HyperGraph and SuperHyperGraph Theory with Applications

Takaaki Fujita, Florentin Smarandache HyperGraph and SuperHyperGraph Theory with Applications I nd 2 edition Foundations, Definitions, and Theoretical Models Neutrosophic Science International Association (NSIA) Publishing House Gallup - Guayaquil United States of America – Ecuador 2026

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Editor: Neutrosophic Science International Association (NSIA) Publishing House https://fs.unm.edu/NSIA/ Division of Mathematics and Sciences University of New Mexico 705 Gurley Ave., Gallup Campus NM 87301, United States of America University of Guayaquil Av. Kennedy and Av. Delta “Dr. Salvador Allende” University Campus Guayaquil 090514, Ecuador Peer-Reviewers: Maikel Leyva-Vázquez Facultad de Ciencias Matemáticas y Físicas Universidad de Guayaquil, Guayas, ECUADOR [email protected] Jesús Rafael Hechavarría Hernández Facultad de Ingenierías, Arquitectura y Ciencias de la Naturaleza Universidad ECOTEC, ECUADOR [email protected] Victor Christianto Malang Institute of Agriculture (IPM), Malang, INDONESIA [email protected] Muhammad Aslam Faculty of Science, King Abdulaziz University, Jeddah, SAUDI ARABIA [email protected] ISBN 978-1-59973-846-8

https://fs.unm.edu/NSIA/

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Table of Contents 1 Introduction 1.1 Graph, Hypergraph, and Superhypergraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Applications of Graph, HyperGraph, and SuperHyperGraph . . . . . . . . . . . . . . . . . . 1.3 Our Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 7 8 8 2 Preliminaries: Basic SuperHyperGraph Theory 2.1 Graphs and Hypergraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 SuperHyperGraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Generalization Theorem for SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . 9 9 10 15 3 Basic Definition for SuperHyperGraph 3.1 Simple, Uniform, and Nonempty-tier SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . 3.2 Matrix for SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 SuperHyperGraph Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 SuperHyperGraph Entropy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5 Similarity and Metric on SuperHyperGraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6 SuperHypergraph Morphism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7 SuperHyperGraph Partitioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.8 SuperHyperGraph Coloring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.9 SuperHyperGraph Domination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.10 Sombor index of SuperHypergraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.11 SuperHyperGraph Labeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.12 SuperHyperGraph Grammar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 21 23 26 31 33 35 37 40 43 46 50 53 4 Some Particular SuperHyperGraphs 4.1 Directed SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Bidirected SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Multidirected SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Mixed SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 Multi-SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 Semi-SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.7 Pseudo-SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8 Directed Multi-SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.9 Signed SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.10 Weighted SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.11 SuperHyperTree and SuperHypertree Decomposition . . . . . . . . . . . . . . . . . . . . . . 4.12 Complete 𝑛-SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.13 co-SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 57 59 61 63 64 67 69 70 73 75 78 82 83 3

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4.14 Perfect SuperHyperGraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 4.15 Line SuperHyperGraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 4.16 Total Superhypergraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 4.17 Interval SuperHypergraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 4.18 Unimodular SuperHypergraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 4.19 Probabilistic Superhypergraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 4.20 Balanced SuperHypergraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 4.21 Spatial Superhypergraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 4.22 Planar SuperHypergraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 4.23 Outerplanar SuperHypergraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 4.24 Multimodal Superhypergraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 4.25 Lattice Superhypergraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 4.26 Hyperbolic Superhypergraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 4.27 Directed Acyclic Superhypergraphs (dash) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 4.28 Meta-SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 4.29 Regular SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122 4.30 Intersection SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 4.31 Bipartite SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 4.32 Threshold SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 4.33 Fractional SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 4.34 Cycle SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 4.35 Friendship SuperHyperGraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 4.36 Wheel SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 4.37 Submodular SuperHypergraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 4.38 Multipartite SuperHypergraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 4.39 Annotated HyperGraph and SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . 143 4.40 Chordal 𝑛-SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 4.41 Kneser SuperHypergraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 4.42 Turán SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 4.43 Book SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 4.44 Pancake SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 4.45 Connected 𝑛-SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 5 Uncertain SuperHyperGraph 161 5.1 Fuzzy 𝑛-SuperHyperGraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 5.1.1 Fuzzy Graph and Fuzzy HyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . 162 5.1.2 Fuzzy 𝑛-SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 5.2 Intuitionistic Fuzzy SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166 5.3 Neutrosophic SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 5.4 Plithogenic SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 5.5 Uncertain SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 5.6 Functorial SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 5.7 Soft SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 5.8 Rough SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 5.9 Fuzzy Directed 𝑛-Superhypergraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 5.10 Single-valued Neutrosophic Directed 𝑛-Superhypergraph . . . . . . . . . . . . . . . . . . . . 191 5.11 Fuzzy Tolerance SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 5.12 Neutrosophic HyperEdgeWeighted 𝑛-SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . 196 6 Applications of SuperHyperGraph 199 6.1 Molecular SuperHyperGraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199 6.2 Competition SuperHyperGraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202 6.3 Property SuperHyperGraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 6.4 Knowledge SuperHyperGraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206 6.5 Quantum Superhypergraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 6.6 SuperHyperGraph Containter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 6.7 SuperHyperGraph-Based Food Web . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 6.8 Crystal SuperHyperGraph in material sciences . . . . . . . . . . . . . . . . . . . . . . . . . . 217 4

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6.9 SuperHyperGraph Neural Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 6.10 Semantic SuperHyperGraphs in Psychology . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 6.11 Behavioral SuperHyperGraphs in Social Sciences . . . . . . . . . . . . . . . . . . . . . . . . 223 6.12 SuperHyperGraph Signal Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 6.13 Bond SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 6.14 Brain Hypergraphs in Neuroscience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230 6.15 Legal Citation SuperHyperGraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232 6.16 River Network SuperHyperGraphs in Geoscientific and Civil Applications . . . . . . . . . . . 234 6.17 Transportation Network SuperHyperGraphs in Geoscientific and Civil Applications . . . . . . 236 6.18 SuperHyperGraph Learning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238 6.19 SuperHyperGraph Attention Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 7 Extensional Definitions: (𝑚, 𝑛)-SuperHyperGraph 245 7.1 (𝑚, 𝑛)-SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 7.2 Fuzzy (𝑚, 𝑛)-SuperHyperGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 8 SuperHyperStructure 253 8.1 HyperStructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 8.2 SuperHyperStructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256 9 Conclusion 259 A Appendix: Multi-Intersection Graph 263 Appendix (List of Tables) 265 5

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HyperGraph and SuperHyperGraph Theory with Applications Takaaki Fujita 1 ∗ and Florentin Smarandache2 1 Independent Researcher, Tokyo, Japan. Email: [email protected] 2 University of New Mexico, Gallup Campus, NM 87301, USA. Email: [email protected] Abstract Hypergraphs generalize this framework by allowing hyperedges that connect more than two vertices [1]. Superhypergraphs further enrich the model through iterated powerset constructions, capturing hierarchical and self-referential structures among hyperedges [2]. An (𝑚, 𝑛)-SuperHyperGraph is a mathematical structure in which each vertex corresponds to an (𝑚, 𝑛)-superhyperfunction defined on a base set, while the hyperedges group such functions together to represent higher-order relationships and contextual connections. Systematic research on SuperHyperGraphs is still relatively limited compared with the extensive literature on graphs and hypergraphs. To help bridge this gap, this book presents a survey of fundamental and advanced concepts related to SuperHy-perGraphs. Our aim is twofold: (i) to increase the visibility and accessibility of SuperHyperGraph theory and thereby stimulate further research, and (ii) to deepen the mathematical understanding of their structures among researchers and practitioners who work with graph- and hypergraph-based models. Keywords SuperHyperGraph Theory, HyperGraph Theory, (𝑚, 𝑛)Superhypergraph Theory, Uncertain Graph Theory, Graph Applications

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Chapter 1 Introduction 1.1 Graph, Hypergraph, and Superhypergraph Network modeling often relies on graphs, where entities are represented by vertices and binary relations are represented by edges [3]. However, classical graphs can be inadequate for describing complex networks in which three or more entities interact simultaneously. Hypergraphs address this limitation by allowing each hyperedge to connect an arbitrary nonempty subset of vertices, thereby capturing higher-order interactions [4]. Despite their expressive power, hypergraphs may still be insufficient for representing layered, nested, and inherently hierarchical relationships that arise in many real-world systems. To bridge this gap, the notion of a SuperHyperGraph was introduced by F. Smarandache. A SuperHyperGraph employs iterative powerset-based constructions to encode nested connectivity patterns and multi-level relations [2,5], and has attracted substantial recent attention [6, 7]. Graphs and hypergraphs provide intuitive visual metaphors for complex systems and support a wide range of applications in artificial intelligence, network science, data mining, informatics, chemistry, physics, and beyond [8–11]. By explicitly accommodating hierarchical and multi-level relationships, SuperHyperGraphs offer a robust framework for modeling and analyzing the intricate structures encountered in modern networked data (e.g.. [12–14, 14–16]). Table 1.1 summarizes the key distinctions among graphs, hypergraphs, and superhypergraphs. Throughout this book, 𝑛 is taken to be a natural number unless stated otherwise. Table 1.1: Key distinctions among graph, hypergraph, and superhypergraph Concept Notation Edge Type Extension Mechanism Graph [3] 𝐺 = (𝑉, 𝐸) 𝐸 ⊆ {{𝑢, 𝑣} | 𝑢, 𝑣 ∈ 𝑉, 𝑢 ≠ 𝑣} Hypergraph [17] 𝐻 = (𝑉, 𝐸) 𝐸 ⊆ P (𝑉) \ {∅} Superhypergraph [2] SHG (𝑛) = (𝑉0 , 𝑉, 𝐸) 𝑉 ⊆ P 𝑛 (𝑉0 ), 𝐸 ⊆ P (𝑉) Standard edges connect exactly two vertices. Hyperedges may join any nonempty subset of vertices. Applies an 𝑛-fold powerset to capture nested structure. Notation. P (𝑋) = { 𝐴 ⊆ 𝑋} and P 0 (𝑋) = 𝑋, P 𝑘+1 (𝑋) = P ( P 𝑘 (𝑋) ). Advantages of Using SuperHyperGraphs include several well-known benefits, such as: • Naturally modeling hierarchical structures through iterated powersets. • Representing multiway, multi-level relations within a unified framework. • Containing graphs [3], multi-graphs [18,19], subset-vertex graphs [20–22], hypergraphs [17], supergraph [23], h-model [24], Quasi-SuperHyperGraphs [5], Powerset Graph [25], k-chain free sets [26], johnson [27], kneser graphs [28], and multi-hypergraphs [29] as special (flattened) instances. 7

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Chapter 1. Introduction • Supporting rich attribute systems (fuzzy, intuitionstic fuzzy, neutrosophic, plithogenic [2]) at every level. • Providing a better fit for real hierarchical systems such as curricula or supply-chain networks. 1.2 Applications of Graph, HyperGraph, and SuperHyperGraph Graph, HyperGraph, and SuperHyperGraph structures have been investigated in a wide range of application domains. Representative examples are summarized in Table 1.2 and 1.3. It should be noted that research on SuperHyperGraphs is still in its early stages, and most existing work remains theoretical at the time of writing. Consequently, future studies are expected to include more practical research supported by computational experiments, machine-learning techniques, and detailed case studies conducted by domain experts. Table 1.2: Applied graph, hypergraph, and superhypergraph models Application domain Graph model HyperGraph model SuperHyperGraph model Generic network Molecular structure Competition / ecology Knowledge / semantics Property-based system Semi-structured network Quantum system Semantic relations Bonding Chemical reactions Legal citation network Fuzzy uncertainty Neutrosophic uncertainty Plithogenic uncertainty Soft-set based modeling Rough approximation Graph Molecular Graph [30] Competition Graph [33] Knowledge Graph [36] Property Graph [40] SemiGraph [42] Quantum Graph [44, 45] Semantic Graph [48] Bond Graph [51, 52] Chemical Graph [54] Legal Citation Graph [59] Fuzzy Graph [61] Neutrosophic Graph [64, 65] Plithogenic Graph [69] Soft Graph [72] Rough Graph [74] HyperGraph Molecular HyperGraph [31] Competition HyperGraph [34] Knowledge HyperGraph [37, 38] Property HyperGraph [41] SemiHyperGraph [43] Quantum HyperGraph [46] Semantic HyperGraph [49] Bond HyperGraph [53] Chemical HyperGraph [55, 56] Legal Citation HyperGraph [60] Fuzzy HyperGraph [62] Neutrosophic HyperGraph [66, 67] Plithogenic HyperGraph [70] Soft HyperGraph [72] Rough HyperGraph [75] SuperHyperGraph Molecular SuperHyperGraph [32] Competition SuperHyperGraph [35] Knowledge SuperHyperGraph [39] Property SuperHyperGraph [41] Semi-SuperHyperGraph [5] Quantum SuperHyperGraph [47] Semantic SuperHyperGraph [50] Bond SuperHyperGraph [53] Chemical SuperHyperGraph [57, 58] Legal Citation SuperHyperGraph [60] Fuzzy SuperHyperGraph [63] Neutrosophic SuperHyperGraph [68] Plithogenic SuperHyperGraph [13, 71] Soft SuperHyperGraph [73] Rough SuperHyperGraph [73] Table 1.3: Additional applied graph, hypergraph, and superhypergraph models (Part 2) Application domain Graph model HyperGraph model SuperHyperGraph model Higher-order containers Ecological food webs Graph Container Graph-based Food Web HyperGraph Container [76–78] Hypergraph-based Food Web [80] Crystal and lattice structures Neural architectures Crystal Graph [81–83] Graph Neural Network [86–88] Social and behavioral modeling Signal processing on networks Behavioral Graphs in Social Sciences [92, 93] Graph Signal Processing [94, 95] Brain connectivity River basin and watershed systems Brain Graphs [98, 99] River Network Graphs Crystal HyperGraph [84] Hypergraph Neural Network [4, 89, 90] Behavioral HyperGraphs in Social Sciences [50] Hypergraph Signal Processing [96, 97] Brain HyperGraphs [100] River Network HyperGraphs [101] Transportation and logistics Transportation Network Graphs SuperHyperGraph Container [79] SuperHyperGraph-Based Food Web [80] Crystal SuperHyperGraph [85] SuperHyperGraph Neural Network [91] Behavioral SuperHyperGraphs in Social Sciences [50] SuperHyperGraph Signal Processing [53] Brain SuperHyperGraphs [100] River Network SuperHyperGraphs [101] Transportation Network SuperHyperGraphs [101] 1.3 Transportation Graphs [101] Network Hyper- Our Contributions From the above discussion, it is clear that SuperHyperGraphs are highly important for modeling hierarchical and multiway structures. However, systematic research on SuperHyperGraphs remains relatively limited compared with the extensive literature on graphs and hypergraphs. To help bridge this gap, this book provides a survey of fundamental and advanced concepts related to SuperHyperGraphs. Our aim is twofold: (i) to increase the visibility and accessibility of SuperHyperGraph theory and thereby stimulate further research, and (ii) to deepen the mathematical understanding of these structures among researchers and practitioners who work with graph- and hypergraph-based models. This book primarily focuses on theoretical developments. We sincerely hope that further computational experiments and real-world case studies will be carried out by experts in the relevant domains. 8

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[beta]

Chapter 2

Preliminaries: Basic SuperHyperGraph Theory

We collect the basic terminology and notation used in what follows. Unless explicitly stated otherwise, all
graphs considered are finite, undirected, and loopless; multiple edges are allowed only when this is specified.

2.1

Graphs and Hypergraphs

Graphs and hypergraphs are fundamental combinatorial models for discrete structures. A classical (undirected)
graph can be viewed as a special case of a hypergraph in which every edge contains exactly two vertices [3].
In contrast, a classical hypergraph permits an edge to connect an arbitrary (finite) number of vertices, making
it suitable for representing multiway relationships [1, 102, 103]. We briefly present the definitions along with
the related concepts.
Definition 2.1.1 (Graph). [3] A (simple) graph is an ordered pair 𝐺 = (𝑉, 𝐸) where 𝑉 is a nonempty finite
set of vertices and

𝐸 ⊆ {𝑢, 𝑣} | 𝑢, 𝑣 ∈ 𝑉, 𝑢 ≠ 𝑣
is a set of unordered pairs of distinct vertices, called edges.
Definition 2.1.2 (Subgraph). [3] Let 𝐺 = (𝑉, 𝐸) be a graph. A graph 𝐻 = (𝑉 ′ , 𝐸 ′ ) is called a subgraph of 𝐺
if

𝑉 ′ ⊆ 𝑉 and 𝐸 ′ ⊆ {𝑢, 𝑣} ∈ 𝐸 | 𝑢, 𝑣 ∈ 𝑉 ′ .
Definition 2.1.3 (Base set). A base (ground) set is a fixed finite set 𝑆 from which higher-level objects are
generated:
𝑆 = { 𝑥 | 𝑥 belongs to the chosen domain }.
All structures introduced below ultimately draw their elements from 𝑆.
Definition 2.1.4 (Powerset). [104, 105] Given a set 𝑋, its powerset is
P (𝑋) := { 𝐴 ⊆ 𝑋 }.
We also use the nonempty powerset
P∗ (𝑋) := P (𝑋) \ {∅}.
Definition 2.1.5 (Hypergraph [1, 17]). A hypergraph is a pair 𝐻 = (𝑉 (𝐻), 𝐸 (𝐻)) where

𝑉 (𝐻) ≠ ∅ and 𝐸 (𝐻) ⊆ P∗ 𝑉 (𝐻) .
Throughout this book both 𝑉 (𝐻) and 𝐸 (𝐻) are assumed to be finite. Elements of 𝑉 (𝐻) are called vertices,
and elements of 𝐸 (𝐻) are called hyperedges.
We present below a concrete example of a HyperGraph.
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Chapter 2. Preliminaries: Basic SuperHyperGraph Theory
Example 2.1.6 (A simple collaboration hypergraph). Consider the finite set of researchers
𝑉 (𝐻) := {Alice, Bob, Carol, Dave}.
We define three research teams (hyperedges) by
𝑒 1 := {Alice, Bob, Carol},

𝑒 2 := {Bob, Dave},

𝑒 3 := {Alice, Dave},

and set
𝐸 (𝐻) := { 𝑒 1 , 𝑒 2 , 𝑒 3 }.
Each 𝑒 𝑖 is a nonempty subset of 𝑉 (𝐻), so

𝐸 (𝐻) ⊆ P∗ 𝑉 (𝐻) ,
and therefore
𝐻 := 𝑉 (𝐻), 𝐸 (𝐻)



is a hypergraph in the sense of the definition above.
Real-life interpretation.
• The vertices Alice, Bob, Carol, Dave represent individual researchers in a laboratory.
• The hyperedge 𝑒 1 represents a large joint project involving Alice, Bob, and Carol.
• The hyperedges 𝑒 2 and 𝑒 3 represent smaller projects: one between Bob and Dave, and one between Alice
and Dave.
In this way, hyperedges encode multi-person collaborations, which cannot be captured by ordinary (pairwise)
graph edges alone.

2.2

SuperHyperGraphs

A SuperHyperGraph carries this idea further by forming vertices and edges from iterated powersets of a
base set; this viewpoint has appeared in several recent contexts [7, 106, 107]. Reported applications include,
among others, molecular structure modeling, complex network analysis, and signal processing [108–112].
Throughout, the level 𝑛 is a fixed nonnegative integer. We briefly present the definitions along with the related
concepts.
Definition 2.2.1 (Iterated powerset). [113–115] For 𝑘 ∈ N0 define
P 0 (𝑋) := 𝑋,


P 𝑘+1 (𝑋) := P P 𝑘 (𝑋) .

For the nonempty version set
0
P∗ (𝑋) := 𝑋,

P∗

 𝑘+1


(𝑋) := P∗ (P∗ ) 𝑘 (𝑋) .

Example 2.2.2 (Iterated powerset for a finite base set). Let the base set be
𝑋 := {𝑎, 𝑏}.
𝑘
We compute the first few iterated powersets P 𝑘 (𝑋) and their nonempty versions P∗ (𝑋).
Step 1: Level 𝑘 = 0. By Definition 2.2.1,
0
P∗ (𝑋) = 𝑋 = {𝑎, 𝑏}.

P 0 (𝑋) = 𝑋 = {𝑎, 𝑏},

Step 2: Level 𝑘 = 1 (ordinary powerset). The powerset of 𝑋 is

P 1 (𝑋) = P (𝑋) = ∅, {𝑎}, {𝑏}, {𝑎, 𝑏} .
10

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Chapter 2. Preliminaries: Basic SuperHyperGraph Theory
The nonempty powerset of 𝑋 is

1
P∗ (𝑋) = P∗ (𝑋) = {𝑎}, {𝑏}, {𝑎, 𝑏} ,
obtained by removing the empty set ∅.
Step 3: Level 𝑘 = 2 (powerset of the powerset). Now P 1 (𝑋) has four elements, so its powerset has 24 = 16
subsets:


P 2 (𝑋) = P P 1 (𝑋) = P {∅, {𝑎}, {𝑏}, {𝑎, 𝑏}} .
Explicitly,

P 2 (𝑋) = ∅, {∅}, {{𝑎}}, {{𝑏}}, {{𝑎, 𝑏}}, {∅, {𝑎}}, {∅, {𝑏}}, {∅, {𝑎, 𝑏}},
{{𝑎}, {𝑏}}, {{𝑎}, {𝑎, 𝑏}}, {{𝑏}, {𝑎, 𝑏}}, {∅, {𝑎}, {𝑏}}, {∅, {𝑎}, {𝑎, 𝑏}},
{∅, {𝑏}, {𝑎, 𝑏}}, {{𝑎}, {𝑏}, {𝑎, 𝑏}}, {∅, {𝑎}, {𝑏}, {𝑎, 𝑏}} .
The nonempty version at level 2 is obtained by removing the empty set:
2


P∗ (𝑋) = P∗ (P∗ ) 1 (𝑋) = P∗ {{𝑎}, {𝑏}, {𝑎, 𝑏}} .
Since (P∗ ) 1 (𝑋) has three elements, its nonempty powerset has 23 − 1 = 7 elements:

2
P∗ (𝑋) = {{𝑎}}, {{𝑏}}, {{𝑎, 𝑏}}, {{𝑎}, {𝑏}}, {{𝑎}, {𝑎, 𝑏}},
{{𝑏}, {𝑎, 𝑏}}, {{𝑎}, {𝑏}, {𝑎, 𝑏}} .
Interpretation.
• Level 0 (P 0 (𝑋)): the original “atomic” elements 𝑎, 𝑏.
• Level 1 (P 1 (𝑋)): all subsets of {𝑎, 𝑏}, such as {𝑎} or {𝑎, 𝑏}.
• Level 2 (P 2 (𝑋)): sets whose elements are themselves subsets of {𝑎, 𝑏}; for instance {{𝑎}, {𝑎, 𝑏}} is one
element of P 2 (𝑋).
Thus the iterated powerset construction builds higher and higher levels of “sets of sets”, which is the basic
combinatorial mechanism behind 𝑛-SuperHyperGraphs and related hierarchical structures.
We state below the definition of an 𝑛-SuperHyperGraph. Although several types of definitions exist for an
𝑛-SuperHyperGraph, we present one representative example below.
Definition 2.2.3 (𝑛-SuperHyperGraph).
𝑛-SuperHyperGraph over 𝑉0 is a triple

[2, 112, 116] Fix a finite base set 𝑉0 and a level 𝑛 ∈ N0 . An

SHG (𝑛) = 𝑉, 𝐸, 𝜕 ,

where
• 𝑉 ⊆ P 𝑛 (𝑉0 ) is a finite set of 𝑛-supervertices;
• 𝐸 ⊆ P (𝑉) is a finite set of (super)edge identifiers;
• 𝜕 : 𝐸 → P∗ (𝑉) is an incidence map sending each edge to a nonempty finite subset of 𝑉.
For 𝑒 ∈ 𝐸, the set 𝜕 (𝑒) ⊆ 𝑉 is called the (super)edge incidence set.
Table 2.1 re-presents the conceptual relationships among Graphs, HyperGraphs, and SuperHyperGraphs.
SuperHyperGraphs are expected to provide a clear and expressive framework for representing hierarchical
network structures that arise in real-world systems.
We present below concrete examples of SuperHyperGraphs.
11

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Chapter 2. Preliminaries: Basic SuperHyperGraph Theory
Structure
Graph

Definition (Core Idea)
A graph 𝐺 = (𝑉, 𝐸) where every
edge connects exactly two vertices.
A hypergraph 𝐻 = (𝑉, 𝐸) where
each hyperedge 𝑒 ∈ 𝐸 is any
nonempty subset of 𝑉.

HyperGraph

Relation to Other Structures
Special case of a hypergraph where
all hyperedges have size 2.
Generalizes graphs by allowing
edges of arbitrary cardinality.
Graphs embed as hypergraphs with
all hyperedges of size 2.
Strict extension of hypergraphs. For
𝑛 = 0 one recovers ordinary hypergraphs; for 𝑛 ≥ 1 vertices and
edges are built from iterated powersets, enabling hierarchical and
multi-level structures.

An 𝑛-SuperHyperGraph SHG (𝑛) =
(𝑉, 𝐸, 𝜕) where 𝑉 ⊆ P 𝑛 (𝑉0 ) are 𝑛supervertices and 𝜕 : 𝐸 → P∗ (𝑉)
gives 𝑛-superedges.

SuperHyperGraph

Table 2.1: Conceptual relationships among Graphs, HyperGraphs, and SuperHyperGraphs
Example 2.2.4 (University curriculum bundle network as a 2-SuperHyperGraph). A university curriculum is a
structured collection of courses organized into modules and programs to guide students’ academic progression
[117, 118]. We model a small part of a university curriculum in which courses are grouped into modules, and
several modules are combined into degree-program patterns.
Step 1: Base set and iterated powersets. Let the finite base set of atomic courses be

𝑉0 := Math101, CS101, AI201, DS201 .
By Definition 2.2.1,
P 1 (𝑉0 ) = P (𝑉0 ),


P 2 (𝑉0 ) = P P (𝑉0 ) .

Elements of P 1 (𝑉0 ) are modules (sets of courses), while elements of P 2 (𝑉0 ) are families of modules.
For readability, define the following modules (elements of P 1 (𝑉0 )):
𝑀core := {Math101, CS101},

𝑀AI := {CS101, AI201},

𝑀DS := {AI201, DS201}.

Step 2: 2-supervertices. We now form program patterns as subsets of P (𝑉0 ), hence elements of P 2 (𝑉0 ):

𝑣 AI-track := 𝑀core , 𝑀AI , 𝑀DS ,

𝑣 DS-track := 𝑀core , 𝑀DS ,

𝑣 foundation := 𝑀core .
Each of 𝑣 AI-track , 𝑣 DS-track , 𝑣 foundation is a subset of P (𝑉0 ), so

𝑣 AI-track , 𝑣 DS-track , 𝑣 foundation ∈ P P (𝑉0 ) = P 2 (𝑉0 ).
We set the 2-supervertex set

𝑉 := 𝑣 AI-track , 𝑣 DS-track , 𝑣 foundation

⊆ P 2 (𝑉0 ).

Step 3: Superedges and incidence map. We introduce three superedges:
𝐸 := {𝑒 AI-only , 𝑒 DS-only , 𝑒 AI-DS-joint },
and define the incidence map
𝜕 : 𝐸 −→ P∗ (𝑉)
by
𝜕 (𝑒 AI-only ) := { 𝑣 foundation , 𝑣 AI-track },
𝜕 (𝑒 DS-only ) := { 𝑣 foundation , 𝑣 DS-track },
12

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14.

Chapter 2. Preliminaries: Basic SuperHyperGraph Theory 𝜕 (𝑒 AI-DS-joint ) := { 𝑣 AI-track , 𝑣 DS-track }. Each 𝜕 (𝑒) is a nonempty subset of 𝑉, so 𝜕 (𝑒) ∈ P∗ (𝑉). Thus SHG (2) := 𝑉, 𝐸, 𝜕 is a valid 2-SuperHyperGraph in the sense of Definition 2.2.3. Real-life interpretation. • The base set 𝑉0 collects individual courses. • Each element of P (𝑉0 ) is a course module (e.g. “core mathematics and programming” or “artificial intelligence”). • Each 2-supervertex 𝑣 ∈ 𝑉 is a program pattern: a finite family of modules that could be offered as a coherent track. • Each superedge 𝑒 ∈ 𝐸 bundles several such patterns that the university regards as mutually comparable or administratively linked (e.g. AI-only, DS-only, or joint AI-DS offering). The double powerset level 𝑛 = 2 is essential: vertices are not single modules, but families of modules, capturing the idea that program design operates on sets of module combinations rather than on individual courses alone. Example 2.2.5 (Multi-hospital monitoring protocols as a 3-SuperHyperGraph). Multi-hospital management has become increasingly necessary in recent years [119, 120]. We model how different hospitals organize multi-level vital-sign monitoring protocols. Step 1: Base set and first-level combinations. Let the base set of atomic vital signals be 𝑉0 := HR, BP, SpO2 , Temp . Then P 1 (𝑉0 ) = P (𝑉0 ), P 2 (𝑉0 ) = P P (𝑉0 ) , P 3 (𝑉0 ) = P P 2 (𝑉0 ) . For clinical use, we define several monitoring templates (elements of P 1 (𝑉0 )): 𝑇cardiac := {HR, BP, SpO2 }, 𝑇resp := {SpO2 , Temp}, 𝑇basic := {HR, BP}. Step 2: Second-level bundles (protocol families). We combine templates into protocol families, which are subsets of P (𝑉0 ) and hence elements of P 2 (𝑉0 ): 𝑄 emerg := {𝑇cardiac , 𝑇resp }, 𝑄 routine := {𝑇basic }. Since each 𝑄 • is a subset of P (𝑉0 ), we have 𝑄 emerg , 𝑄 routine ∈ P P (𝑉0 ) = P 2 (𝑉0 ). Step 3: Third-level vertices (hospital-specific portfolios). Each hospital chooses certain protocol families. Thus a hospital portfolio is a subset of P 2 (𝑉0 ), i.e. an element of P 3 (𝑉0 ). Define 𝑣 HospitalA := { 𝑄 emerg , 𝑄 routine }, 𝑣 HospitalB := { 𝑄 emerg }. {𝑄 emerg , 𝑄 routine } ⊆ P 2 (𝑉0 ), {𝑄 emerg } ⊆ P 2 (𝑉0 ), Because we obtain 𝑣 HospitalA , 𝑣 HospitalB ∈ P P 2 (𝑉0 ) = P 3 (𝑉0 ). 13

#p12
#p272

15.

Chapter 2. Preliminaries: Basic SuperHyperGraph Theory We set the 3-supervertex set 𝑉 := 𝑣 HospitalA , 𝑣 HospitalB ⊆ P 3 (𝑉0 ). Step 4: Superedges and incidence map. We describe national guidelines that relate these hospital portfolios. Introduce 𝐸 := {𝑒 national-minimum , 𝑒 high-intensity }, with incidence map 𝜕 : 𝐸 → P∗ (𝑉) given by 𝜕 (𝑒 national-minimum ) := { 𝑣 HospitalA , 𝑣 HospitalB }, 𝜕 (𝑒 high-intensity ) := { 𝑣 HospitalA }. Again each 𝜕 (𝑒) is a nonempty subset of 𝑉, so 𝜕 (𝑒) ∈ P∗ (𝑉). Hence SHG (3) := 𝑉, 𝐸, 𝜕 is a 3-SuperHyperGraph in the sense of Definition 2.2.3. Real-life interpretation. • Level 0 (𝑉0 ): individual vital signs (HR, BP, SpO2 , Temp). • Level 1 (P 1 (𝑉0 )): monitoring templates, each a concrete set of vital signs to measure together (e.g. cardiac or respiratory). • Level 2 (P 2 (𝑉0 )): protocol families combining templates for emergency or routine monitoring. • Level 3 (P 3 (𝑉0 )): hospital portfolios collecting protocol families actually implemented at each hospital. • Superedges collect hospital portfolios subject to national or regional guidelines (e.g. “national minimum” vs. “high-intensity” monitoring requirements). The triple powerset level 𝑛 = 3 is crucial here: vertices are portfolios of protocol families, which captures the genuinely hierarchical nature of real-world clinical monitoring policies. The theorem is stated as follows. Theorem 2.2.6 (𝑛-SuperHyperGraphs generalize hypergraphs). Every finite hypergraph can be realized as an 𝑛SuperHyperGraph (in particular, as a 0-SuperHyperGraph). Consequently, the class of 𝑛-SuperHyperGraphs strictly generalizes the class of hypergraphs. Proof. Let 𝐻 = (𝑉 (𝐻), 𝐸 (𝐻)) be a finite hypergraph in the sense that 𝑉 (𝐻) ≠ ∅, 𝐸 (𝐻) ⊆ P∗ 𝑉 (𝐻) := P 𝑉 (𝐻) \ {∅}, so each 𝑒 ∈ 𝐸 (𝐻) is a nonempty subset of 𝑉 (𝐻). We construct a 0-SuperHyperGraph that reproduces 𝐻 exactly. Step 1: Base set and level. Take the base set 𝑉0 := 𝑉 (𝐻) and the level 𝑛 := 0. By Definition 2.2.1, we have P 0 (𝑉0 ) = 𝑉0 . 14

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Chapter 2. Preliminaries: Basic SuperHyperGraph Theory
Step 2: Supervertices. Set
𝑉 := 𝑉0 = 𝑉 (𝐻).
Then, by P 0 (𝑉0 ) = 𝑉0 , we obtain

𝑉 ⊆ P 0 (𝑉0 ),

so 𝑉 is an admissible set of 0-supervertices.
Step 3: Superedges and incidence map. Define the superedge set
𝐸 := 𝐸 (𝐻),
and the incidence map
𝜕 : 𝐸 −→ P∗ (𝑉)
by
𝜕 (𝑒) := 𝑒

for all 𝑒 ∈ 𝐸 .

Since 𝐸 (𝐻) ⊆ P∗ (𝑉 (𝐻)) and 𝑉 = 𝑉 (𝐻), each 𝑒 ∈ 𝐸 satisfies
∅ ≠ 𝑒 ⊆ 𝑉,
hence
𝜕 (𝑒) = 𝑒 ∈ P∗ (𝑉)

(∀ 𝑒 ∈ 𝐸).

Therefore
SHG (0) := (𝑉, 𝐸, 𝜕)
is a 0-SuperHyperGraph according to Definition 2.2.3.
Step 4: Identification with the original hypergraph. In the hypergraph 𝐻, the incidence relation is given
by membership 𝑣 ∈ 𝑒 ⊆ 𝑉 (𝐻). In the constructed 0-SuperHyperGraph SHG (0) , the incidence is given by
𝑣 ∈ 𝜕 (𝑒). But by construction
𝜕 (𝑒) = 𝑒 for all 𝑒 ∈ 𝐸,
so for all 𝑣 ∈ 𝑉 and 𝑒 ∈ 𝐸,
𝑣∈𝑒

⇐⇒

𝑣 ∈ 𝜕 (𝑒).

Hence the identity maps
𝑉 (𝐻) → 𝑉,

𝑣 ↦→ 𝑣,

𝐸 (𝐻) → 𝐸,

preserve both vertices, edges, and incidence. Thus 𝐻 and SHG

(0)

𝑒 ↦→ 𝑒,

are isomorphic as incidence structures.

Consequently, every hypergraph is (up to isomorphism) a 0-SuperHyperGraph. Since 𝑛-SuperHyperGraphs
are defined for all 𝑛 ∈ N0 and allow vertices in P 𝑛 (𝑉0 ) for 𝑛 ≥ 1, they form a strictly larger class of objects,
which contains all hypergraphs as the special case 𝑛 = 0.
□

2.3

Generalization Theorem for SuperHyperGraph

SuperHyperGraphs can generalize a wide variety of graphs and related mathematical structures. As an
illustrative starting point, we explicitly examine how SuperHyperGraphs generalize several classical objects,
namely abstract simplicial complexes, finite matroids, and balanced incomplete block designs (BIBDs).
Definition 2.3.1 (Abstract simplicial complex). (cf. [121, 122]) Let 𝑉 be a finite, nonempty set. A family
Δ ⊆ P (𝑉) is called an abstract simplicial complex on 𝑉 if
1. Δ ≠ ∅;
2. (downward closed) whenever 𝜎 ∈ Δ and 𝜏 ⊆ 𝜎, then 𝜏 ∈ Δ.
The elements of Δ are called simplices; singletons {𝑣} with 𝑣 ∈ 𝑉 are the vertices of the complex. We write
𝐾 = (𝑉, Δ) for an abstract simplicial complex.
15

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[beta]

Chapter 2. Preliminaries: Basic SuperHyperGraph Theory
Example 2.3.2 (Abstract simplicial complex of a filled triangle). Let
𝑉 := {1, 2, 3}.
Define

Δ := ∅, {1}, {2}, {3}, {1, 2}, {1, 3}, {2, 3}, {1, 2, 3} .
Then Δ ⊆ P (𝑉) is nonempty and downward closed: whenever 𝜎 ∈ Δ and 𝜏 ⊆ 𝜎, the face 𝜏 is also in Δ (for
instance, {1, 2, 3} ∈ Δ implies that all of {1, 2}, {1, 3}, {2, 3} and singletons {1}, {2}, {3} lie in Δ). Thus
𝐾 = (𝑉, Δ) is an abstract simplicial complex representing a filled triangle with vertices 1, 2, 3.
Definition 2.3.3 (Finite matroid). [123–125] Let 𝐸 be a finite, nonempty set. A family I ⊆ P (𝐸) is called a
system of independent sets on 𝐸 if it satisfies:

1. ∅ ∈ I (nonempty);
2. (hereditary) if 𝐼 ∈ I and 𝐽 ⊆ 𝐼, then 𝐽 ∈ I;
3. (exchange axiom) if 𝐼, 𝐽 ∈ I and |𝐼 | < |𝐽 |, then there exists 𝑒 ∈ 𝐽 \ 𝐼 such that 𝐼 ∪ {𝑒} ∈ I.

A pair 𝑀 = (𝐸, I) satisfying the above axioms is called a finite matroid.
Example 2.3.4 (Cycle matroid of a triangle graph). Let 𝐺 be the simple graph with vertex set
𝑉 (𝐺) := {𝑎, 𝑏, 𝑐}
and edge set
𝐸 := {𝑒 1 , 𝑒 2 , 𝑒 3 }
where
𝑒 1 = 𝑎𝑏,

𝑒 2 = 𝑏𝑐,

𝑒 3 = 𝑐𝑎.

Define

I := 𝐼 ⊆ 𝐸

𝐼 does not contain all three edges simultaneously .

Explicitly,

I = ∅, {𝑒 1 }, {𝑒 2 }, {𝑒 3 }, {𝑒 1 , 𝑒 2 }, {𝑒 1 , 𝑒 3 }, {𝑒 2 , 𝑒 3 } .
Then (𝐸, I) satisfies the matroid axioms: ∅ ∈ I, it is hereditary under taking subsets, and the exchange axiom
holds (any smaller independent set can be extended by an edge from a larger independent set while staying
independent). Hence 𝑀 = (𝐸, I) is a finite matroid, called the cycle matroid of the triangle graph 𝐺.
Definition 2.3.5 (Balanced incomplete block design (BIBD)). [126, 127] Let 𝑋 be a finite set of points with
|𝑋 | = 𝑣. A balanced incomplete block design with parameters (𝑣, 𝑏, 𝑟, 𝑘, 𝜆) is a pair
D = (𝑋, B),
where B is a multiset of 𝑏 blocks 𝐵 ⊆ 𝑋 such that

1. (block size) each block has the same size 𝑘: |𝐵| = 𝑘 for all 𝐵 ∈ B;
2. (replication) each point appears in exactly 𝑟 blocks: for every 𝑥 ∈ 𝑋,
{ 𝐵 ∈ B | 𝑥 ∈ 𝐵 } = 𝑟;
3. (pair balance) every unordered pair of distinct points appears together in exactly 𝜆 blocks: for all
{𝑥, 𝑦} ⊆ 𝑋, 𝑥 ≠ 𝑦,
{ 𝐵 ∈ B | {𝑥, 𝑦} ⊆ 𝐵 } = 𝜆.
16

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Chapter 2. Preliminaries: Basic SuperHyperGraph Theory
Example 2.3.6 (A (3, 3, 2, 2, 1) balanced incomplete block design). Let the point set be
𝑋 := {1, 2, 3},

𝑣 = |𝑋 | = 3.

Consider the multiset of blocks

B := {1, 2}, {1, 3}, {2, 3} ,
so 𝑏 = |B| = 3. Each block has size 𝑘 = 2.
Each point appears in exactly 𝑟 = 2 blocks:
1 occurs in {1, 2}, {1, 3};

2 occurs in {1, 2}, {2, 3};

3 occurs in {1, 3}, {2, 3}.

Every unordered pair of distinct points appears together in exactly 𝜆 = 1 block:
{1, 2} in {1, 2},

{1, 3} in {1, 3},

{2, 3} in {2, 3}.

Thus
D = (𝑋, B)
is a balanced incomplete block design with parameters (𝑣, 𝑏, 𝑟, 𝑘, 𝜆) = (3, 3, 2, 2, 1).
Theorem 2.3.7. Every abstract simplicial complex, every finite matroid, and every balanced incomplete block
design can be represented as a 1-SuperHyperGraph on a suitable base set. More precisely:
(1)
1. For each abstract simplicial complex 𝐾 = (𝑉, Δ) there exists a 1-SuperHyperGraph SHGSC
= (𝑉SC , 𝐸 SC )
(1)
such that 𝐾 is recovered from SHGSC .
(1)
2. For each finite matroid 𝑀 = (𝐸, I) there exists a 1-SuperHyperGraph SHGM
= (𝑉M , 𝐸 M ) from which
𝑀 is recovered.

3. For each BIBD D = (𝑋, B) there exists a 1-SuperHyperGraph SHGB(1) = (𝑉B , 𝐸 B ) from which D is
recovered.
Consequently, these three classes are special cases of 1-SuperHyperGraphs, obtained by imposing additional
axioms on the superedge family.
Proof. We treat the three cases separately, always working with the same pattern: choose a base set 𝑉0 , construct
a 1-SuperHyperGraph (𝑉, 𝐸) with 𝑉, 𝐸 ⊆ P (𝑉0 ), and then show that the original structure is uniquely recovered
from (𝑉, 𝐸).
(1) Abstract simplicial complexes. Let 𝐾 = (𝑉, Δ) be an abstract simplicial complex. Choose the base set
𝑉0 := 𝑉 .
Define
𝑉SC :=



{𝑣} 𝑣 ∈ 𝑉

⊆ P (𝑉0 ),

𝐸 SC := Δ \ {∅} ⊆ P (𝑉0 ).
Then both 𝑉SC and 𝐸 SC are subsets of P (𝑉0 ), so
(1)
SHGSC
:= (𝑉SC , 𝐸 SC )

is a 1-SuperHyperGraph on 𝑉0 .
Conversely, from (𝑉SC , 𝐸 SC ) we reconstruct 𝐾 as follows. The vertex set is

𝑉 = 𝑣 ∈ 𝑉0 {𝑣} ∈ 𝑉SC ,
and the simplices form
Δ := 𝐸 SC ∪ {∅}.
17

19.

[beta]

Chapter 2. Preliminaries: Basic SuperHyperGraph Theory
Downward closedness of Δ comes exactly from the simplicial complex axioms; in the 1-SuperHyperGraph
representation this appears as a closure property of 𝐸 SC inside P (𝑉0 ). Thus there is a one-to-one correspondence
between abstract simplicial complexes on 𝑉 and 1-SuperHyperGraphs of the above form on base 𝑉0 = 𝑉,
showing that 1-SuperHyperGraphs generalize simplicial complexes.
(2) Finite matroids. Let 𝑀 = (𝐸, I) be a finite matroid. Take the base set
𝑉0 := 𝐸 .
Define
𝑉M :=



{𝑒} 𝑒 ∈ 𝐸

⊆ P (𝑉0 ),

𝐸 M := I \ {∅} ⊆ P (𝑉0 ).
Again 𝑉M , 𝐸 M ⊆ P (𝑉0 ), so
(1)
SHGM
:= (𝑉M , 𝐸 M )

is a 1-SuperHyperGraph on base 𝑉0 .
(1)
From SHGM
we recover the matroid as follows. The ground set is

𝐸 = 𝑒 ∈ 𝑉0 {𝑒} ∈ 𝑉M ,

and the independent sets are
I := 𝐸 M ∪ {∅}.
The hereditary and exchange axioms of a matroid are now simply additional conditions on the superedge family
𝐸M :
• hereditary: 𝐼 ∈ 𝐸 M , 𝐽 ⊆ 𝐼 implies either 𝐽 ∈ 𝐸 M or 𝐽 = ∅;
• exchange: if 𝐼, 𝐽 ∈ 𝐸 M and |𝐼 | < |𝐽 |, then there exists 𝑒 ∈ 𝐽 \ 𝐼 with 𝐼 ∪ {𝑒} ∈ 𝐸 M .
Thus every finite matroid can be seen as a 1-SuperHyperGraph satisfying specific incidence–regularity constraints on its superedges, and conversely any 1-SuperHyperGraph of this form determines a matroid. Hence
finite matroids are special cases of 1-SuperHyperGraphs.
(3) Balanced incomplete block designs. Let D = (𝑋, B) be a (𝑣, 𝑏, 𝑟, 𝑘, 𝜆) BIBD. Choose the base set
𝑉0 := 𝑋.
We represent the design as a 1-SuperHyperGraph by taking

𝑉B := {𝑥} 𝑥 ∈ 𝑋 ⊆ P (𝑉0 ),
𝐸 B := { 𝐵 ⊆ 𝑋 | 𝐵 ∈ B } ⊆ P (𝑉0 ).
Thus

SHGB(1) := (𝑉B , 𝐸 B )

is a 1-SuperHyperGraph whose superedges are exactly the blocks of the design.
Conversely, given a 1-SuperHyperGraph (𝑉B , 𝐸 B ) constructed in this way, we recover the design:
𝑋 = {𝑥 ∈ 𝑉0 | {𝑥} ∈ 𝑉B },

B = 𝐸B

(viewing B as a multiset if some blocks repeat). The BIBD constraints (constant block size 𝑘, constant
replication number 𝑟, and constant pair count 𝜆) become numerical regularity conditions on the superedge
family 𝐸 B :
• |𝐵| = 𝑘 for all 𝐵 ∈ 𝐸 B ;
18

20.

[beta]

Chapter 2. Preliminaries: Basic SuperHyperGraph Theory
• for each 𝑥 ∈ 𝑋, the number of superedges containing 𝑥 is 𝑟;
• for each unordered pair {𝑥, 𝑦} ⊆ 𝑋 with 𝑥 ≠ 𝑦, the number of superedges containing {𝑥, 𝑦} is 𝜆.
Hence BIBDs are 1-SuperHyperGraphs endowed with this specific incidence-regularity pattern.
In all three cases the construction is functorial and invertible at the level of underlying sets and incidence families:
an abstract simplicial complex, a finite matroid, or a BIBD is completely encoded by a 1-SuperHyperGraph
with appropriately constrained superedge family, and conversely such constrained 1-SuperHyperGraphs recover
exactly these structures. Therefore abstract simplicial complexes, finite matroids, and balanced incomplete
block designs are all generalized by the 1-SuperHyperGraph framework.
□
From the above observations, we obtain Theorem 2.3.8 (cf. [128]).
Theorem 2.3.8 (Universality of SuperHyperGraphs). Every one of the following structures can be faithfully
represented as an 𝑛-SuperHyperGraph:
• Ordinary graphs;
• Hypergraphs [17];
• Multigraphs [18, 19];
• Supergraphs [23];
• Multihypergraphs [29];
• Quasi-SuperHyperGraphs [5];
• 𝑛-th power graphs [129];
• Subset-Vertex graphs [22];
• Subset-Vertex multigraphs [20];
• ℎ-models [24];
• 𝑘-chain-free hypergraphs [26];
• Power set graphs [130];
• 𝑛-th power set graphs [128];
• Johnson graphs [131];
• Kneser graphs [132];
• Sets [105];
• Multisets [133];
• Iterated multisets [134];
• Powersets [130];
• 𝑛-th powersets [135];
• Abstract simplicial complexes [136, 137];
• Finite matroids [125];
• Balanced incomplete block designs (BIBDs) [127, 138].

19

21.

Chapter 2. Preliminaries: Basic SuperHyperGraph Theory 20

22.

Chapter 3 Basic Definition for SuperHyperGraph In the areas of graphs and hypergraphs, a wide variety of operations and graph structures have been defined and studied in terms of their properties. The same is true for SuperHyperGraphs. We present the core definitions and fundamental properties of SuperHyperGraphs. 3.1 Simple, Uniform, and Nonempty-tier SuperHyperGraph A simple SuperHyperGraph forbids parallel superedges; the incidence map is injective, ensuring that each superedge has a unique incidence pattern. A 𝑘–uniform SuperHyperGraph is one in which every superedge is incident with exactly 𝑘 supervertices. This extends the notion of uniformity from classical uniform hypergraphs to the multi-level setting of SuperHyperGraphs, modeling higher-order interactions of fixed arity [17,139,140]. A nonempty-tier SuperHyperGraph requires that every supervertex belongs to the iterated nonempty powersets at each hierarchical level, thereby excluding empty sets throughout the entire multi-tier construction. Definition 3.1.1 (Simple 𝑛-SuperHyperGraph). Let 𝑉0 be a finite base set and let 𝑛 ∈ N0 . An 𝑛-SuperHyperGraph over 𝑉0 is a triple SHG (𝑛) = (𝑉, 𝐸, 𝜕), where 𝑉 ⊆ P 𝑛 (𝑉0 ), 𝐸 is a finite set of superedges, and 𝜕 : 𝐸 −→ P∗ (𝑉) is the incidence map that assigns to each superedge 𝑒 ∈ 𝐸 a nonempty set 𝜕 (𝑒) ⊆ 𝑉 of 𝑛-supervertices. The 𝑛-SuperHyperGraph SHG (𝑛) is called simple if it has no parallel superedges, that is, if the incidence map 𝜕 is injective: ∀ 𝑒 1 , 𝑒 2 ∈ 𝐸 : 𝑒 1 ≠ 𝑒 2 =⇒ 𝜕 (𝑒 1 ) ≠ 𝜕 (𝑒 2 ). Equivalently, in a simple 𝑛-SuperHyperGraph each superedge is uniquely determined by its incidence set. Definition 3.1.2 (𝑘-uniform 𝑛-SuperHyperGraph). In the setting of Definition 3.1.1, fix an integer 𝑘 ∈ N with 𝑘 ≥ 1. The 𝑛-SuperHyperGraph SHG (𝑛) = (𝑉, 𝐸, 𝜕) is called 𝑘-uniform if every superedge is incident with exactly 𝑘 𝑛-supervertices, i.e., ∀𝑒 ∈ 𝐸 : 𝜕 (𝑒) = 𝑘. In particular, 1-uniform 𝑛-SuperHyperGraphs have superedges incident with a single 𝑛-supervertex, while 2uniform 𝑛-SuperHyperGraphs may be viewed as superedge analogues of ordinary (hyper)edges between pairs of 𝑛-supervertices. 21

#p268
#p22

23.

Chapter 3. Basic Definition for SuperHyperGraph Example 3.1.3 (A 2-uniform 1-SuperHyperGraph: paired joint-degree programmes). Fix the base set of courses 𝑉0 := {Math, Phys, CS, Econ}. At level 𝑛 = 1 we consider subsets of 𝑉0 , so P 1 (𝑉0 ) = P (𝑉0 ). Define the following 1-supervertices, each representing a joint-degree programme built from a bundle of courses: 𝑣 1 := {Math, Phys}, 𝑣 2 := {Math, CS}, 𝑣 3 := {CS, Econ}. Set 𝑉 := {𝑣 1 , 𝑣 2 , 𝑣 3 } ⊆ P 1 (𝑉0 ). We now describe how some pairs of programmes are jointly administered (for example, they share a common committee or accreditation process). Introduce two superedges 𝐸 := {𝑒 12 , 𝑒 23 } with incidence map 𝜕 : 𝐸 −→ P∗ (𝑉) given by 𝜕 (𝑒 12 ) := {𝑣 1 , 𝑣 2 }, 𝜕 (𝑒 23 ) := {𝑣 2 , 𝑣 3 }. By construction, 𝜕 (𝑒 12 ) = 𝜕 (𝑒 23 ) = 2, so every superedge is incident with exactly two 1-supervertices. Hence SHG (1) := (𝑉, 𝐸, 𝜕) is a 2-uniform 1-SuperHyperGraph in the sense of Definition 3.1.2. Each superedge represents a pair of joint-degree programmes that are coordinated at the administrative level. Example 3.1.4 (A 3-uniform 2-SuperHyperGraph: tri-regional emergency clusters). Let the base set of response resources be 𝑉0 := {𝑟 1 , 𝑟 2 , 𝑟 3 , 𝑟 4 , 𝑟 5 , 𝑟 6 }, where each 𝑟 𝑖 is, say, an ambulance or fire unit. At level 1 we group resources into local response cells. For instance, 𝐶1 := {𝑟 1 , 𝑟 2 }, 𝐶2 := {𝑟 3 , 𝑟 4 }, 𝐶3 := {𝑟 5 , 𝑟 6 } ∈ P 1 (𝑉0 ) = P (𝑉0 ). At level 𝑛 = 2 we group these cells into regional clusters, so vertices live in P 2 (𝑉0 ) = P P (𝑉0 ) . Define three 2-supervertices 𝑣 𝐴 := {𝐶1 , 𝐶2 }, 𝑣 𝐵 := {𝐶2 , 𝐶3 }, 𝑣 𝐶 := {𝐶1 , 𝐶3 }, and set 𝑉 := {𝑣 𝐴, 𝑣 𝐵 , 𝑣 𝐶 } ⊆ P 2 (𝑉0 ). Suppose a national emergency protocol specifies that certain training exercises always involve exactly three regional clusters working together. We model one such exercise by a single superedge 𝐸 := {𝑒 𝐴𝐵𝐶 }, 22

#p22

24.

[beta]

Chapter 3. Basic Definition for SuperHyperGraph
with incidence map
𝜕 : 𝐸 −→ P∗ (𝑉),

𝜕 (𝑒 𝐴𝐵𝐶 ) := {𝑣 𝐴, 𝑣 𝐵 , 𝑣 𝐶 }.

Then
𝜕 (𝑒 𝐴𝐵𝐶 ) = 3,
so every superedge (here, the unique one) is incident with exactly three 2-supervertices. Therefore
SHG (2) := (𝑉, 𝐸, 𝜕)
is a 3-uniform 2-SuperHyperGraph.
In this model, each 2-supervertex represents a nested group of resources (local cells within a regional cluster),
and the single superedge encodes a tri-regional emergency exercise involving exactly three such clusters.
Definition 3.1.5 (Nonempty-tier 𝑛-SuperHyperGraph). Let 𝑉0 be a nonempty base set and define the nonempty
iterated powersets recursively by
0
P∗ (𝑉0 ) := 𝑉0 ,

P∗

 𝑘+1

(𝑉0 ) := P∗ (P∗ ) 𝑘 (𝑉0 )



(𝑘 ∈ N0 ),

where P∗ (𝑋) := P (𝑋) \ {∅} denotes the nonempty powerset of 𝑋.
An 𝑛-SuperHyperGraph
SHG (𝑛) = (𝑉, 𝐸, 𝜕)
over 𝑉0 is called nonempty-tier if its vertex set is contained in the nonempty iterated powerset:
𝑛
𝑉 ⊆ P∗ (𝑉0 ).
In this case, every 𝑛-supervertex is built recursively from nonempty sets at each tier, so that no empty set
appears in the construction from 𝑉0 up to level 𝑛. Together with the condition 𝜕 (𝑒) ∈ P∗ (𝑉) for all 𝑒 ∈ 𝐸, this
ensures that the entire hierarchy (base elements, intermediate tiers, vertices, and superedges) is free of empty
components.

3.2

Matrix for SuperHyperGraph

A matrix is a rectangular array of numbers or symbols representing linear transformations, relationships, or
structured data in mathematical applications [141, 142]. Derived notions such as fuzzy matrices [143, 144],
bimatrices [145–147], and neutrosophic matrices [148, 149] are also well known.
A SuperHyperGraph matrix encodes the incidence between all tiered supervertices and superedges in the form
of a binary table, providing a natural generalization of the classical incidence matrices used for graphs and
hypergraphs. This construction extends the ideas behind the matrix for graphs [150, 151] and the matrix for
hypergraphs [17, 152] to the multi-level setting of SuperHyperGraphs. The definition is given as follows.
Definition 3.2.1 (Hypergraph matrix (incidence matrix)). [17] Let 𝐻 = (𝑉, 𝐸) be a finite hypergraph, where
𝑉 = {𝑣 1 , . . . , 𝑣 𝑛 },

𝐸 = {𝑒 1 , . . . , 𝑒 𝑚 }.

The hypergraph matrix (also called the incidence matrix) of 𝐻 is the 𝑛 × 𝑚 matrix
𝑀 (𝐻) = (𝑎 𝑖 𝑗 )1≤𝑖 ≤𝑛, 1≤ 𝑗 ≤𝑚
with rows indexed by vertices and columns indexed by hyperedges, whose entries are defined by
(
1, if 𝑣 𝑖 ∈ 𝑒 𝑗 ,
𝑎𝑖 𝑗 =
0, if 𝑣 𝑖 ∉ 𝑒 𝑗 .
Equivalently, the 𝑗-th column of 𝑀 (𝐻) is the characteristic column vector of the hyperedge 𝑒 𝑗 ⊆ 𝑉.
Definition 3.2.2 (Superhypergraph matrix). Let H (𝑛) = (𝑉0 , 𝑉1 , . . . , 𝑉𝑛 ; 𝐸, 𝜕) be an 𝑛-superhypergraph, where
23

25.

Chapter 3. Basic Definition for SuperHyperGraph • 𝑉0 is a nonempty base set of vertices, • for each tier 𝑖 ∈ {1, . . . , 𝑛}, the 𝑖-th tier vertex set 𝑉𝑖 is a family of nonempty iterated subsets, for example 𝑉𝑖 ⊆ (P ∗ ) 𝑖 (𝑉0 ), • 𝑉 := 𝑉0 ∪ 𝑉1 ∪ · · · ∪ 𝑉𝑛 is the total vertex set, and 𝐸 is a nonempty family of superedges, • 𝜕 : 𝐸 → P ∗ (𝑉) is the boundary map that assigns to each superedge 𝑒 ∈ 𝐸 the nonempty set of (possibly higher-tier) vertices incident with 𝑒. Assume 𝑉 = {𝑤 1 , . . . , 𝑤 𝑁 }, 𝐸 = {𝑒 1 , . . . , 𝑒 𝑀 }. The superhypergraph matrix of H (𝑛) is the 𝑁 × 𝑀 matrix 𝑀 H (𝑛) = (𝑏 𝑝𝑞 )1≤ 𝑝≤ 𝑁 , 1≤𝑞 ≤ 𝑀 , with rows indexed by all vertices 𝑤 𝑝 ∈ 𝑉 (from all tiers) and columns indexed by superedges 𝑒 𝑞 ∈ 𝐸, whose entries are defined by ( 1, if 𝑤 𝑝 ∈ 𝜕 (𝑒 𝑞 ), 𝑏 𝑝𝑞 = 0, if 𝑤 𝑝 ∉ 𝜕 (𝑒 𝑞 ). Equivalently, the 𝑞-th column of 𝑀 H (𝑛) is the characteristic column vector of the incident vertex set 𝜕 (𝑒 𝑞 ) ⊆ 𝑉. If the rows of 𝑀 H (𝑛) are ordered so that 𝑉0 , 𝑉1 , . . . , 𝑉𝑛 form consecutive blocks, then the matrix naturally decomposes into block rows corresponding to the different tiers: 𝑀0 © ª 𝑀1 ®® 𝑀 H (𝑛) = . ® , .. ® ® « 𝑀𝑛 ¬ where 𝑀𝑖 has one row for each vertex in 𝑉𝑖 and the same 𝑀 columns indexed by the superedges in 𝐸. In the special case 𝑛 = 0 and 𝑉0 = 𝑉, the superhypergraph matrix 𝑀 H (0) reduces to the usual hypergraph matrix 𝑀 (𝐻). Example 3.2.3 (One-tier superhypergraph matrix for a small project structure). Consider a 1-superhypergraph modelling two developers and one joint team. Base vertices: 𝑉0 := {Dev1 , Dev2 }. First-tier vertices (team-level group): 𝑉1 := 𝑇 , 𝑇 := {Dev1 , Dev2 }. The total vertex set is 𝑉 := 𝑉0 ∪ 𝑉1 = {Dev1 , Dev2 , 𝑇 }. We define two superedges: 𝐸 := {𝑒 1 , 𝑒 2 }, with boundary map 𝜕 (𝑒 1 ) := {Dev1 , 𝑇 }, 𝜕 (𝑒 2 ) := {Dev2 , 𝑇 }. Here 𝑒 1 represents a task that involves developer 1 and the team as a whole, while 𝑒 2 involves developer 2 and the team. Ordering the vertices as 𝑤 1 = Dev1 , 𝑤 2 = Dev2 , 24 𝑤 3 = 𝑇,

26.

[beta]

Chapter 3. Basic Definition for SuperHyperGraph
and the superedges as 𝑒 1 , 𝑒 2 , the superhypergraph matrix is
1

©
𝑀 H (1) = (𝑏 𝑝𝑞 ) = 0
«1

0
ª
1® ,
1¬

where, for example, the entry 𝑏 31 = 1 encodes that the team vertex 𝑇 is incident with 𝑒 1 , and 𝑏 12 = 0 encodes
that Dev1 is not incident with 𝑒 2 .
Example 3.2.4 (Two-tier superhypergraph matrix for a nested team hierarchy). Consider a 2-superhypergraph
describing employees, subteams, and a department.
Base vertices (employees):
𝑉0 := {𝑝, 𝑞, 𝑟 }.
First-tier vertices (subteams):
𝑃 := {𝑝, 𝑞},

𝑄 := {𝑞, 𝑟},

𝑉1 := {𝑃, 𝑄}.

Second-tier vertex (department grouping subteams 𝑃 and 𝑄):
𝑆 := {𝑃, 𝑄},

𝑉2 := {𝑆}.

Thus the total vertex set is
𝑉 := 𝑉0 ∪ 𝑉1 ∪ 𝑉2 = {𝑝, 𝑞, 𝑟, 𝑃, 𝑄, 𝑆}.
We introduce three superedges that connect different tiers:
𝐸 := {𝑒 1 , 𝑒 2 , 𝑒 3 },
with boundary map
𝜕 (𝑒 1 ) := {𝑝, 𝑃, 𝑆},

𝜕 (𝑒 2 ) := {𝑞, 𝑃, 𝑄, 𝑆},

𝜕 (𝑒 3 ) := {𝑟, 𝑄}.

For instance, 𝑒 1 encodes an initiative involving employee 𝑝, subteam 𝑃, and the department 𝑆; 𝑒 2 involves 𝑞
and both subteams plus the department; 𝑒 3 is specific to 𝑟 and subteam 𝑄.
Order the vertices as
𝑤 1 = 𝑝, 𝑤 2 = 𝑞, 𝑤 3 = 𝑟, 𝑤 4 = 𝑃, 𝑤 5 = 𝑄, 𝑤 6 = 𝑆,
and keep the superedge order 𝑒 1 , 𝑒 2 , 𝑒 3 . The superhypergraph matrix is then
1
©
0


0
𝑀 H (2) = (𝑏 𝑝𝑞 ) = 
1

0
«1

0
1
0
1
1
1

0
ª
0®
®
1®
®.
0®
®
1®
0¬

Each row block corresponds to a tier: rows 1–3 for employees 𝑉0 , rows 4–5 for subteams 𝑉1 , and row 6 for the
department 𝑉2 . For example, 𝑏 46 = 0 does not appear since there is no sixth column; instead, 𝑏 41 = 1 records
that subteam 𝑃 is incident with 𝑒 1 , and 𝑏 63 = 0 shows that the department 𝑆 is not incident with 𝑒 3 .
The theorem is written as follows.
Theorem 3.2.5 (Superhypergraph matrix generalizes the hypergraph matrix). Let 𝐻 = (𝑉 (𝐻), 𝐸 (𝐻)) be a
finite hypergraph with

𝑉 (𝐻) = {𝑣 1 , . . . , 𝑣 𝑛 },
𝐸 (𝐻) = {𝑒 1 , . . . , 𝑒 𝑚 } ⊆ P∗ 𝑉 (𝐻) .
Let 𝑀 (𝐻) = (𝑎 𝑖 𝑗 )1≤𝑖 ≤𝑛, 1≤ 𝑗 ≤𝑚 be its hypergraph (incidence) matrix, defined by
(
1, if 𝑣 𝑖 ∈ 𝑒 𝑗 ,
𝑎𝑖 𝑗 =
0, if 𝑣 𝑖 ∉ 𝑒 𝑗 .
25

27.

Chapter 3. Basic Definition for SuperHyperGraph Consider the 0-SuperHyperGraph SHG (0) := (𝑉, 𝐸, 𝜕) defined by 𝑉 := 𝑉 (𝐻), Let 𝑀 SHG (0) 𝐸 := 𝐸 (𝐻), 𝜕 (𝑒) := 𝑒 (∀𝑒 ∈ 𝐸). = (𝑏 𝑖 𝑗 )1≤𝑖 ≤𝑛, 1≤ 𝑗 ≤𝑚 be its superhypergraph matrix, defined by ( 𝑏𝑖 𝑗 = 1, if 𝑣 𝑖 ∈ 𝜕 (𝑒 𝑗 ), 0, if 𝑣 𝑖 ∉ 𝜕 (𝑒 𝑗 ). Then 𝑀 SHG (0) = 𝑀 (𝐻). In particular, the notion of a superhypergraph matrix strictly generalizes the usual hypergraph matrix, obtained as the special case 𝑛 = 0. Proof. By construction we have, for every 𝑗, 𝜕 (𝑒 𝑗 ) = 𝑒 𝑗 ⊆ 𝑉 = 𝑉 (𝐻). Hence, for all indices 𝑖, 𝑗, ( 1, if 𝑣 𝑖 ∈ 𝜕 (𝑒 𝑗 ), 0, if 𝑣 𝑖 ∉ 𝜕 (𝑒 𝑗 ), ( 1, if 𝑣 𝑖 ∈ 𝑒 𝑗 , 0, if 𝑣 𝑖 ∉ 𝑒 𝑗 . 𝑏𝑖 𝑗 = 𝑎𝑖 𝑗 (∀ 𝑖, 𝑗), 𝑏𝑖 𝑗 = becomes 𝑏𝑖 𝑗 = Therefore, by comparing with the definition of 𝑎 𝑖 𝑗 , so 𝑀 SHG (0) = 𝑀 (𝐻). Since for 𝑛 ≥ 1 a superhypergraph allows vertices in higher iterated powersets and incidence with higher-tier objects, its matrix extends the usual hypergraph matrix beyond the case 𝑛 = 0. Hence the superhypergraph matrix generalizes the hypergraph matrix. □ 3.3 SuperHyperGraph Products Graph products combine two graphs into a new one, with vertices paired and edges defined via specific product rules systematically [153–155]. Related concepts such as Directed Graph Products [156], Fuzzy Graph Products [157–159], and Neutrosophic Graph Products [160, 161] are also well established. A hypergraph product combines two hypergraphs into a new one, pairing vertices and constructing hyperedges according to a specified rule [162, 163]. A SuperHypergraph product forms an 𝑛-SuperHyperGraph from two factors, pairing supervertices and aggregating superedges through iterated powerset-based construction and connectivity. We recall that a (finite) hypergraph is a pair 𝐻 = (𝑉 (𝐻), 𝐸 (𝐻)) with 𝑉 (𝐻) ≠ ∅ and 𝐸 (𝐻) ⊆ P∗ (𝑉 (𝐻)). Definition 3.3.1 (Hypergraph product). [162, 163] Let 𝐻1 = (𝑉1 , 𝐸 1 ) and 𝐻2 = (𝑉2 , 𝐸 2 ) be hypergraphs. A hypergraph product is a binary operation ⊠ on hypergraphs such that 𝐻1 ⊠ 𝐻2 = (𝑉1 × 𝑉2 , 𝐸 (𝐻1 ⊠ 𝐻2 )), where the edge set 𝐸 (𝐻1 ⊠ 𝐻2 ) is specified by a rule that generalizes a chosen graph product. Typical examples are the Cartesian, direct, lexicographic, and square products defined below. 26

#p273

28.

Chapter 3. Basic Definition for SuperHyperGraph Definition 3.3.2 (Cartesian product of hypergraphs). [163] Let 𝐻1 = (𝑉1 , 𝐸 1 ) and 𝐻2 = (𝑉2 , 𝐸 2 ) be hypergraphs. The Cartesian product 𝐻 = 𝐻1 □𝐻2 is the hypergraph with 𝑉 (𝐻) = 𝑉1 × 𝑉2 , and edge set 𝐸 (𝐻) = {𝑥} × 𝑓 | 𝑥 ∈ 𝑉1 , 𝑓 ∈ 𝐸 2 ∪ 𝑒 × {𝑦} | 𝑒 ∈ 𝐸 1 , 𝑦 ∈ 𝑉2 . Each hyperedge of 𝐻1 □𝐻2 is thus either “horizontal” ({𝑥} × 𝑓 ) or “vertical” (𝑒 × {𝑦}). Definition 3.3.3 (Minimal rank–preserving direct product). (cf. [164]) Let 𝐻1 = (𝑉1 , 𝐸 1 ) and 𝐻2 = (𝑉2 , 𝐸 2 ) be hypergraphs. For 𝑒 𝑖 ∈ 𝐸 𝑖 put 𝑟 𝑒−1 ,𝑒2 := min{|𝑒 1 |, |𝑒 2 |}. ⊩ The minimal rank–preserving direct product 𝐻 = 𝐻1 × 𝐻2 is the hypergraph with vertex set 𝑉 (𝐻) = 𝑉1 × 𝑉2 and edge set n o 𝐸 (𝐻) := 𝑒 ⊆ 𝑉1 × 𝑉2 ∃ 𝑒 1 ∈ 𝐸 1 , 𝑒 2 ∈ 𝐸 2 : |𝑒| = 𝑟 𝑒−1 ,𝑒2 , 𝑝 𝑖 (𝑒) ⊆ 𝑒 𝑖 , | 𝑝 𝑖 (𝑒)| = 𝑟 𝑒−1 ,𝑒2 (𝑖 = 1, 2) , where 𝑝 1 , 𝑝 2 denote the coordinate projections 𝑉1 × 𝑉2 → 𝑉1 , 𝑉2 . Equivalently, 𝑒 = {(𝑥1 , 𝑦 1 ), . . . , (𝑥𝑟 , 𝑦 𝑟 )} is an edge of 𝐻 if 𝑟 = 𝑟 𝑒−1 ,𝑒2 for some 𝑒 1 ∈ 𝐸 1 , 𝑒 2 ∈ 𝐸 2 and {𝑥1 , . . . , 𝑥𝑟 } ∈ {𝑒 1 , subset of 𝑒 1 }, {𝑦 1 , . . . , 𝑦 𝑟 } ∈ {𝑒 2 , subset of 𝑒 2 }, with at least one of these sets equal to the corresponding 𝑒 𝑖 . Definition 3.3.4 (Lexicographic product of hypergraphs). (cf. [165,166]) Let 𝐻1 = (𝑉1 , 𝐸 1 ) and 𝐻2 = (𝑉2 , 𝐸 2 ) be hypergraphs. The lexicographic product 𝐻 = 𝐻1 ◦ 𝐻2 is the hypergraph with vertex set 𝑉 (𝐻) = 𝑉1 × 𝑉2 and edge set 𝐸 (𝐻) = 𝑒 ⊆ 𝑉 (𝐻) 𝑝 1 (𝑒) ∈ 𝐸 1 , | 𝑝 1 (𝑒)| = |𝑒| ∪ {𝑥} × 𝑒 2 𝑥 ∈ 𝑉1 , 𝑒 2 ∈ 𝐸 2 , where 𝑝 1 : 𝑉1 × 𝑉2 → 𝑉1 is the projection onto the first coordinate. Thus an edge is either a “lift” of an edge of 𝐻1 , with all first coordinates distinct, or a copy of an edge of 𝐻2 anchored at a fixed vertex 𝑥 ∈ 𝑉1 . Definition 3.3.5 (Square product of hypergraphs). (cf. [162, 167]) Let 𝐻1 = (𝑉1 , 𝐸 1 ) and 𝐻2 = (𝑉2 , 𝐸 2 ) be hypergraphs. The square product 𝐻 = 𝐻1 □□ 𝐻2 is the hypergraph with vertex set 𝑉 (𝐻) = 𝑉1 × 𝑉2 and edge set 𝐸 (𝐻) = { 𝑒 1 × 𝑒 2 | 𝑒 1 ∈ 𝐸 1 , 𝑒 2 ∈ 𝐸 2 }. In particular, each edge of 𝐻 is a full Cartesian product of an edge of 𝐻1 and an edge of 𝐻2 . Definition 3.3.6 (Product of 𝑛-SuperHyperGraphs induced by a hypergraph product). Let ⊠ be a fixed hypergraph product as above, i.e. for hypergraphs 𝐻1 = (𝑉1 , 𝐸 1 ) and 𝐻2 = (𝑉2 , 𝐸 2 ) we have 𝐻1 ⊠ 𝐻2 = (𝑉1 × 𝑉2 , 𝐸 1 ⊠ 𝐸 2 ). Let SHG1(𝑛) = (𝑉1 , 𝐸 1 ) and SHG2(𝑛) = (𝑉2 , 𝐸 2 ) be 𝑛-SuperHyperGraphs based on finite sets 𝑉0(1) and 𝑉0(2) , respectively, so that 𝑉𝑖 , 𝐸 𝑖 ⊆ P𝑛 (𝑉0(𝑖) ) (𝑖 = 1, 2). Form the disjoint union 𝑉0 := 𝑉0(1) ⊔ 𝑉0(2) , and let 𝜄𝑖 : 𝑉0(𝑖) ↩→ 𝑉0 (𝑖 = 1, 2) be the natural injections. Extend these injections levelwise to maps 𝜄𝑖(𝑘 ) : P𝑘 (𝑉0(𝑖) ) −→ P𝑘 (𝑉0 ) (𝑘 ≥ 0) by recursion: 𝜄𝑖(0) := 𝜄𝑖 , 𝜄𝑖(𝑘+1) ( 𝐴) := 𝜄𝑖(𝑘 ) (𝑎) | 𝑎 ∈ 𝐴 27 for 𝐴 ∈ P𝑘+1 (𝑉0(𝑖) ).

#p273

29.

[beta]

Chapter 3. Basic Definition for SuperHyperGraph
Define
𝛽(𝑣 1 , 𝑣 2 ) := 𝜄1(𝑛) (𝑣 1 ) ∪ 𝜄2(𝑛) (𝑣 2 ).

𝛽 : 𝑉1 × 𝑉2 −→ P𝑛 (𝑉0 ),

Let 𝐻 := 𝐻1 ⊠ 𝐻2 = (𝑉1 × 𝑉2 , 𝐸 1 ⊠ 𝐸 2 ) be the hypergraph product of the underlying hypergraphs. We define
the SuperHyperGraph product
SHG1(𝑛) ⊠ SHG2(𝑛) := (𝑉 ′ , 𝐸 ′ )
by
𝑉 ′ := 𝛽(𝑉1 × 𝑉2 ) ⊆ P𝑛 (𝑉0 ),

𝐸 ′ := 𝛽[𝑒] | 𝑒 ∈ 𝐸 1 ⊠ 𝐸 2 ⊆ P𝑛 (𝑉0 ),
where 𝛽[𝑒] := {𝛽(𝑣) | 𝑣 ∈ 𝑒} is the pointwise image of 𝑒 under 𝛽.
Then (𝑉 ′ , 𝐸 ′ ) is an 𝑛-SuperHyperGraph on the unified base set 𝑉0(1) ⊔ 𝑉0(2) ; we call it the ⊠-product of
𝑛-SuperHyperGraphs.
Remark 3.3.7. Choosing ⊠ to be, for example, the Cartesian product □, the minimal rank–preserving direct
product, the lexicographic product, or the square product yields the corresponding Cartesian, direct, lexicographic, or square SuperHyperGraph products. When 𝑛 = 0 (so that P0 (𝑉0 ) = 𝑉0 ), the above construction
reduces to the usual hypergraph product on 𝐻1 and 𝐻2 .
For reference, Table 3.1 presents a comparison of graph, hypergraph, and SuperHyperGraph products.
Table 3.1: Comparison of graph, hypergraph, and SuperHyperGraph products
Aspect

Graph products

HyperGraph products

SuperHyperGraph products

Input objects
Vertex set of the
product
Edge / hyperedge /
superedge type

𝐺𝑖 = (𝑉𝑖 , 𝐸𝑖 )
𝑉1 × 𝑉2

𝐻𝑖 = (𝑉𝑖 , 𝐸𝑖 )
𝑉1 × 𝑉2

SHG𝑖 = (𝑉𝑖 , 𝐸𝑖 ) on bases 𝑉0
(1)
(2) 
𝛽 (𝑉1 × 𝑉2 ) ⊆ P𝑛 𝑉0 ⊔ 𝑉0

Edges are 2-element subsets of
𝑉1 × 𝑉2 .

Hyperedges are arbitrary
nonempty subsets of 𝑉1 × 𝑉2 .

Product rule

Edges determined by adjacencies
in 𝐺1 , 𝐺2 (Cartesian, direct,
lexicographic, etc.).

Hierarchy level

Single-level (binary relations on
𝑉).

Hyperedges built from hyperedges
of 𝐻1 , 𝐻2 by a chosen product
rule (Cartesian, direct,
lexicographic, square, etc.).
Single-level higher-order relations
on 𝑉.

Superedges are subsets of
𝛽 (𝑉1 × 𝑉2 ) (sets of
𝑛-supervertices).
Superedges are images 𝛽 [𝑒] of
hyperedges 𝑒 ∈ 𝐸 (𝐻1 ⊠ 𝐻2 ) for
a fixed hypergraph product
𝐻1 ⊠ 𝐻2 .
Multi-level relations on iterated
powersets P𝑛 (𝑉0 ); graphs and
hypergraphs appear as the special
case 𝑛 = 0.

(𝑛)

(𝑖)

Several concrete examples are provided below.
Example 3.3.8 (Cartesian product of two small 1-SuperHyperGraphs). We illustrate the construction for 𝑛 = 1
using the Cartesian product of hypergraphs.
First component. Let the first base set be
𝑉0(1) := {𝑎, 𝑏}.
At level 𝑛 = 1 the 1-supervertices are subsets of 𝑉0(1) . Set

𝑉1 := 𝐴1 , 𝐴2

with

𝐴1 := {𝑎}, 𝐴2 := {𝑎, 𝑏}.

Define a single hyperedge
𝑒 1 := {𝐴1 , 𝐴2 } ⊆ 𝑉1 ,

𝐸 1 := {𝑒 1 }.

Then
SHG1(1) := (𝑉1 , 𝐸 1 )
is a 1-SuperHyperGraph (its underlying hypergraph has vertex set 𝑉1 and edge set 𝐸 1 ).
28

#p29

30.

Chapter 3. Basic Definition for SuperHyperGraph Second component. Let the second base set be 𝑉0(2) := {𝑥, 𝑦}, and define 1-supervertices 𝑉2 := 𝐵1 , 𝐵2 with 𝐵1 := {𝑥}, 𝐵2 := {𝑥, 𝑦}. Again take a single hyperedge 𝑓1 := {𝐵1 , 𝐵2 } ⊆ 𝑉2 , so 𝐸 2 := { 𝑓1 }, SHG2(1) := (𝑉2 , 𝐸 2 ) is a second 1-SuperHyperGraph. Underlying Cartesian product of hypergraphs. Consider the underlying hypergraphs 𝐻1 := (𝑉1 , 𝐸 1 ), 𝐻2 := (𝑉2 , 𝐸 2 ). Their Cartesian product 𝐻 := 𝐻1 □𝐻2 has vertex set 𝑉 (𝐻) = 𝑉1 × 𝑉2 = {( 𝐴1 , 𝐵1 ), ( 𝐴1 , 𝐵2 ), ( 𝐴2 , 𝐵1 ), ( 𝐴2 , 𝐵2 )}, and edge set 𝐸 (𝐻) = {𝐴𝑖 } × 𝑓1 | 𝑖 = 1, 2 ∪ 𝑒 1 × {𝐵 𝑗 } | 𝑗 = 1, 2 . Explicitly, 𝑒 hor 𝐴1 = {( 𝐴1 , 𝐵1 ), ( 𝐴1 , 𝐵2 )}, 𝑒 hor 𝐴2 = {( 𝐴2 , 𝐵1 ), ( 𝐴2 , 𝐵2 )}, 𝑒 ver 𝐵1 = {( 𝐴1 , 𝐵1 ), ( 𝐴2 , 𝐵1 )}, 𝑒 ver 𝐵2 = {( 𝐴1 , 𝐵2 ), ( 𝐴2 , 𝐵2 )}, hor ver ver so 𝐸 (𝐻) = {𝑒 hor 𝐴1 , 𝑒 𝐴2 , 𝑒 𝐵1 , 𝑒 𝐵2 }. Embedding into a product 1-SuperHyperGraph. Form the disjoint union of base sets 𝑉0 := 𝑉0(1) ⊔ 𝑉0(2) = {𝑎, 𝑏, 𝑥, 𝑦}. Since 𝑛 = 1, each 1-supervertex is just a subset of the corresponding base set. We define the embedding 𝛽 : 𝑉1 × 𝑉2 −→ P (𝑉0 ) by taking unions of the underlying subsets: 𝛽(𝑣 1 , 𝑣 2 ) := 𝑣 1 ∪ 𝑣 2 (now viewed as a subset of 𝑉0 ). Thus 𝛽( 𝐴1 , 𝐵1 ) = {𝑎} ∪ {𝑥} = {𝑎, 𝑥}, 𝛽( 𝐴1 , 𝐵2 ) = {𝑎} ∪ {𝑥, 𝑦} = {𝑎, 𝑥, 𝑦}, 𝛽( 𝐴2 , 𝐵1 ) = {𝑎, 𝑏} ∪ {𝑥} = {𝑎, 𝑏, 𝑥}, 𝛽( 𝐴2 , 𝐵2 ) = {𝑎, 𝑏} ∪ {𝑥, 𝑦} = {𝑎, 𝑏, 𝑥, 𝑦}. We take as the vertex set of the product 1-SuperHyperGraph 𝑉 ′ := 𝛽(𝑉1 × 𝑉2 ) = {{𝑎, 𝑥}, {𝑎, 𝑥, 𝑦}, {𝑎, 𝑏, 𝑥}, {𝑎, 𝑏, 𝑥, 𝑦}} ⊆ P1 (𝑉0 ). For each hyperedge 𝑒 ∈ 𝐸 (𝐻) we set 𝛽[𝑒] := {𝛽(𝑣) | 𝑣 ∈ 𝑒} ⊆ 𝑉 ′ , 29

31.

Chapter 3. Basic Definition for SuperHyperGraph and define 𝐸 ′ := {𝛽[𝑒] | 𝑒 ∈ 𝐸 (𝐻)}. Concretely, 𝛽[𝑒 hor 𝐴1 ] = {𝑎, 𝑥}, {𝑎, 𝑥, 𝑦} , 𝛽[𝑒 hor 𝐴2 ] = {𝑎, 𝑏, 𝑥}, {𝑎, 𝑏, 𝑥, 𝑦} , 𝛽[𝑒 ver 𝐵1 ] = {𝑎, 𝑥}, {𝑎, 𝑏, 𝑥} , 𝛽[𝑒 ver 𝐵2 ] = {𝑎, 𝑥, 𝑦}, {𝑎, 𝑏, 𝑥, 𝑦} . Therefore SHG1(1) □SHG2(1) := (𝑉 ′ , 𝐸 ′ ) is a 1-SuperHyperGraph whose vertices are 1-supervertices in P1 (𝑉0 ) and whose hyperedges are induced from the Cartesian product of the underlying hypergraphs. Example 3.3.9 (Square product of two small 1-SuperHyperGraphs). We now use the same level 𝑛 = 1 but take the square product of hypergraphs. Component SuperHyperGraphs. Let 𝑉0(1) := {𝑝, 𝑞}, 𝑉0(2) := {𝑟, 𝑠}. Define 𝑉1 := {𝑃1 , 𝑃2 }, 𝑃1 := {𝑝}, 𝑃2 := {𝑝, 𝑞}, and 𝑒 1 := {𝑃1 , 𝑃2 } ⊆ 𝑉1 , 𝐸 1 := {𝑒 1 }, so SHG1(1) := (𝑉1 , 𝐸 1 ) is a 1-SuperHyperGraph. Similarly, set 𝑉2 := {𝑄 1 , 𝑄 2 }, 𝑄 1 := {𝑟 }, 𝑄 2 := {𝑟, 𝑠}, and 𝑓1 := {𝑄 1 , 𝑄 2 } ⊆ 𝑉2 , 𝐸 2 := { 𝑓1 }, so SHG2(1) := (𝑉2 , 𝐸 2 ) is another 1-SuperHyperGraph. Underlying square product of hypergraphs. Consider the underlying hypergraphs 𝐻1 := (𝑉1 , 𝐸 1 ), 𝐻2 := (𝑉2 , 𝐸 2 ). Their square product 𝐻 := 𝐻1 □□ 𝐻2 has vertex set 𝑉 (𝐻) = 𝑉1 × 𝑉2 = {(𝑃1 , 𝑄 1 ), (𝑃1 , 𝑄 2 ), (𝑃2 , 𝑄 1 ), (𝑃2 , 𝑄 2 )}, and, by definition of the square product, 𝐸 (𝐻) = {𝑒 1 × 𝑓1 }, i.e. a single hyperedge 𝑒 ∗ := 𝑒 1 × 𝑓1 = {(𝑃1 , 𝑄 1 ), (𝑃1 , 𝑄 2 ), (𝑃2 , 𝑄 1 ), (𝑃2 , 𝑄 2 )}. Embedding into a product 1-SuperHyperGraph. Form the combined base set 𝑉0 := 𝑉0(1) ⊔ 𝑉0(2) = {𝑝, 𝑞, 𝑟, 𝑠}. Again, at level 𝑛 = 1 each 1-supervertex is a subset of 𝑉0 . Define 𝛽 : 𝑉1 × 𝑉2 −→ P (𝑉0 ), 𝛽(𝑣 1 , 𝑣 2 ) := 𝑣 1 ∪ 𝑣 2 . 30

32.

[beta]

Chapter 3. Basic Definition for SuperHyperGraph
Hence
𝛽(𝑃1 , 𝑄 1 ) = {𝑝} ∪ {𝑟 } = {𝑝, 𝑟},
𝛽(𝑃1 , 𝑄 2 ) = {𝑝} ∪ {𝑟, 𝑠} = {𝑝, 𝑟, 𝑠},
𝛽(𝑃2 , 𝑄 1 ) = {𝑝, 𝑞} ∪ {𝑟 } = {𝑝, 𝑞, 𝑟 },
𝛽(𝑃2 , 𝑄 2 ) = {𝑝, 𝑞} ∪ {𝑟, 𝑠} = {𝑝, 𝑞, 𝑟, 𝑠}.
Thus the vertex set of the product 1-SuperHyperGraph is
𝑉 ′′ := 𝛽(𝑉1 × 𝑉2 ) = {{𝑝, 𝑟}, {𝑝, 𝑟, 𝑠}, {𝑝, 𝑞, 𝑟 }, {𝑝, 𝑞, 𝑟, 𝑠}} ⊆ P1 (𝑉0 ).
The unique hyperedge 𝑒 ∗ ∈ 𝐸 (𝐻) induces

𝛽[𝑒 ∗ ] = 𝛽(𝑃1 , 𝑄 1 ), 𝛽(𝑃1 , 𝑄 2 ), 𝛽(𝑃2 , 𝑄 1 ), 𝛽(𝑃2 , 𝑄 2 ) = 𝑉 ′′ ,
so we put
𝐸 ′′ := {𝛽[𝑒 ∗ ]}.
Therefore

SHG1(1) □□ SHG2(1) := (𝑉 ′′ , 𝐸 ′′ )

is a 1-SuperHyperGraph whose single 1-superedge connects all four 1-supervertices. It is precisely the product
of the two 1-SuperHyperGraphs induced by the square product of their underlying hypergraphs.

3.4

SuperHyperGraph Entropy

Entropy measures disorder or uncertainty in a system, quantifying missing information or the number of
microscopic configurations accessible to it [168]. Related concepts such as Fuzzy Entropy [169, 170] and
Neutrosophic Entropy [171, 172] are also well known.
SuperHyperGraph entropy quantifies the uncertainty inherent in weighted, multi-level hyperedge connectivity
by employing minimal cut weights to evaluate how much information flows across external partitions of the
supervertex hierarchy [173]. The formulation extends and adapts the principles of graph entropy [174, 175],
and hypergraph entropy [176, 177] to the richer, iterated-powerset structure of SuperHyperGraphs.
Definition 3.4.1 (𝑛-SuperHyperGraph Entropy). [173] Let 𝑉0 be a finite base set and, for each integer 𝑘 ≥ 0,
define the iterated powerset by

P0 (𝑉0 ) := 𝑉0 ,
P𝑘+1 (𝑉0 ) := P P𝑘 (𝑉0 ) ,
where 𝑃(·) denotes the usual powerset.
Fix 𝑛 ∈ N0 and an integer 𝑚 ≥ 1. A weighted 𝑛-SuperHyperGraph is a tuple
SHG (𝑛) = (𝑉, 𝐸, 𝜕, 𝜔, 𝜕𝑉, 𝜒),
where
• 𝑉 ⊆ P𝑛 (𝑉0 ) is a finite set of 𝑛-supervertices,
• 𝐸 is a finite set of 𝑛-superedges,
• 𝜕 : 𝐸 → 𝑃∗ (𝑉) is the incidence map, where P∗ (𝑉) := P (𝑉) \ {∅},
• 𝜔 : 𝐸 → R>0 assigns a strictly positive weight to each 𝑛-superedge,
• 𝜕𝑉 ⊆ 𝑉 is the distinguished set of external 𝑛-supervertices,
• 𝜒 : 𝜕𝑉 → [𝑚] := {1, 2, . . . , 𝑚} labels each external supervertex by one of 𝑚 parties. For 𝐼 ⊆ [𝑚] we
set
𝜕𝑉𝐼 := 𝜒 −1 (𝐼) = { 𝑣 ∈ 𝜕𝑉 : 𝜒(𝑣) ∈ 𝐼 }.
31

#p273

33.

[beta]

Chapter 3. Basic Definition for SuperHyperGraph
For any 𝑊 ⊆ 𝑉 we define the 𝑛-SuperHyperGraph cut

𝐶 (𝑛) (𝑊) := 𝑒 ∈ 𝐸 𝜕 (𝑒) ∩ 𝑊 ≠ ∅, 𝜕 (𝑒) ∩ (𝑉 \ 𝑊) ≠ ∅ ,
and its total cut-weight
∑︁

𝑐 (𝑛) (𝑊) :=

𝜔(𝑒).

𝑒∈𝐶 (𝑛) (𝑊 )

For each nonempty index set 𝐼 ⊆ [𝑚], the 𝑛-SuperHyperGraph entropy of the subsystem 𝐼 is defined by
𝑆 (𝑛) (𝐼) :=

min

𝑊 ⊆𝑉
𝑊∩𝜕𝑉=𝜕𝑉𝐼

𝑐 (𝑛) (𝑊),

provided that the set of admissible 𝑊 is nonempty (otherwise one may set 𝑆 (𝑛) (𝐼) := +∞).
The family


𝑆 (𝑛) (𝐼)

∅ ≠ 𝐼 ⊆ [𝑚]

is called the 𝑛-SuperHyperGraph entropy vector of SHG (𝑛) . When 𝑛 is clear from the context, we simply write
𝑆 (𝑛) and refer to it as the SuperHyperGraph Entropy.
For reference, Table 3.2 presents a comparison of Graph Entropy, HyperGraph Entropy, and SuperHyperGraph
Entropy.
Table 3.2: Comparison of Graph Entropy, HyperGraph Entropy, and SuperHyperGraph Entropy
Aspect

Graph Entropy

HyperGraph Entropy

SuperHyperGraph Entropy

Underlying
structure

Finite graph 𝐺 = (𝑉, 𝐸),
where each edge joins exactly two vertices.

Finite hypergraph 𝐻 =
(𝑉, 𝐸), where each hyperedge 𝑒 ∈ 𝐸 is a nonempty
subset of 𝑉.

Interaction
level

Binary (pairwise) edges;
only 2-vertex interactions are
represented.

Higher-order
interactions
via hyperedges on arbitrary
nonempty vertex subsets.

Entropy construction

Shannon-type entropy 𝐻 ( 𝑝)
of a probability distribution
on 𝑉 or 𝐸, typically induced
by degrees, distances, or centrality measures.

Main focus

Quantifies uncertainty or information content in ordinary network connectivity.

Entropy of a probability distribution on vertices or hyperedges derived from incidence patterns or hyperedge
weights, extending graph entropy to higher-order edges.
Quantifies uncertainty in
higher-order group interactions on a single structural
tier.

Weighted
𝑛SuperHyperGraph
SHG (𝑛)
=
(𝑉, 𝐸, 𝜕, 𝜔, 𝜕𝑉, 𝜒)
with
𝑉 ⊆ P𝑛 (𝑉0 ).
Multi-level and hierarchical
interactions between supervertices formed from iterated
powersets.
Cut-based entropy vector
𝑆 (𝑛) (𝐼) defined by the minimal total weight of superedges crossing admissible cuts separating external
parties 𝐼 ⊆ [𝑚].
Quantifies uncertainty in
weighted, multi-tier superedge connectivity across
hierarchical partitions of the
supervertex system.

Example 3.4.2 (A simple 1-SuperHyperGraph entropy). Let 𝑉0 := {𝑎, 𝑏, 𝑐} and 𝑃0 (𝑉0 ) := 𝑉0 , 𝑃1 (𝑉0 ) :=
𝑃(𝑉0 ). Consider the 1-SuperHyperGraph
SHG (1) = (𝑉, 𝐸, 𝜕, 𝜔, 𝜕𝑉, 𝜒)
with
𝑉 := {{𝑎}, {𝑏}, {𝑎, 𝑏}} ⊆ 𝑃1 (𝑉0 ),

𝐸 := {𝑒 1 , 𝑒 2 },

incidence map
𝜕 (𝑒 1 ) := {{𝑎}, {𝑎, 𝑏}},

𝜕 (𝑒 2 ) := {{𝑏}, {𝑎, 𝑏}},
32

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Chapter 3. Basic Definition for SuperHyperGraph and positive weights 𝜔(𝑒 1 ) := 1, 𝜔(𝑒 2 ) := 2. Let the external supervertices and labels be 𝜕𝑉 := {{𝑎}, {𝑏}}, 𝑚 := 2, 𝜒({𝑎}) := 1, 𝜒({𝑏}) := 2. For 𝐼 ⊆ [𝑚] = {1, 2} we have 𝜕𝑉{1} = {{𝑎}}, 𝜕𝑉{2} = {{𝑏}}. We compute the entropy 𝑆 (1) ({1}). By definition, 𝑆 (1) ({1}) := min 𝑊 ⊆𝑉 𝑊∩𝜕𝑉=𝜕𝑉{1} 𝑐 (1) (𝑊), 𝑐 (1) (𝑊) := ∑︁ 𝜔(𝑒), 𝑒∈𝐶 (1) (𝑊 ) where 𝐶 (1) (𝑊) := { 𝑒 ∈ 𝐸 | 𝜕 (𝑒) ∩ 𝑊 ≠ ∅, 𝜕 (𝑒) ∩ (𝑉 \ 𝑊) ≠ ∅ }. The constraint 𝑊 ∩ 𝜕𝑉 = 𝜕𝑉{1} = {{𝑎}} means that 𝑊 must contain {𝑎} but not {𝑏}. Thus the admissible subsets 𝑊 are 𝑊1 := {{𝑎}}, 𝑊2 := {{𝑎}, {𝑎, 𝑏}}. For 𝑊1 we have 𝑉 \ 𝑊1 = {{𝑏}, {𝑎, 𝑏}} and 𝐶 (1) (𝑊1 ) = {𝑒 1 }, 𝑐 (1) (𝑊1 ) = 𝜔(𝑒 1 ) = 1, since 𝜕 (𝑒 1 ) meets both 𝑊1 and 𝑉 \ 𝑊1 , whereas 𝜕 (𝑒 2 ) does not intersect 𝑊1 . For 𝑊2 we have 𝑉 \ 𝑊2 = {{𝑏}} and 𝐶 (1) (𝑊2 ) = {𝑒 2 }, 𝑐 (1) (𝑊2 ) = 𝜔(𝑒 2 ) = 2, since 𝜕 (𝑒 2 ) meets both 𝑊2 and 𝑉 \ 𝑊2 , whereas 𝜕 (𝑒 1 ) is entirely contained in 𝑊2 . Hence 𝑆 (1) ({1}) = min{𝑐 (1) (𝑊1 ), 𝑐 (1) (𝑊2 )} = min{1, 2} = 1. This value 𝑆 (1) ({1}) = 1 is the 1-SuperHyperGraph entropy of the subsystem corresponding to party 1. 3.5 Similarity and Metric on SuperHyperGraphs Similarity and metric on SuperHyperGraphs evaluate the closeness of multi-level incidence structures by comparing the patterns of their tiered superedges, producing normalized distance values and similarity scores for structured uncertain networks. This notion extends the established ideas of similarity and metric on graphs and on hypergraphs (cf. [17, 178, 179]) to the richer SuperHyperGraph framework. Definition 3.5.1 (Similarity and metric on hypergraphs). [17] Let 𝑉 = {𝑣 1 , . . . , 𝑣 𝑝 } and 𝐸 = {𝑒 1 , . . . , 𝑒 𝑞 } be finite sets. A (simple) hypergraph on (𝑉, 𝐸) is given by a map 𝜕 : 𝐸 → P∗ (𝑉), 𝑒 ↦→ 𝜕 (𝑒), where P∗ (𝑉) is the set of all nonempty subsets of 𝑉. Its incidence matrix is the ( 𝑝 × 𝑞)–matrix 𝑀 (𝐻) = (𝑚 𝑖 𝑗 ) with ( 1, 𝑣 𝑖 ∈ 𝜕 (𝑒 𝑗 ), 𝑚 𝑖 𝑗 := 0, 𝑣 𝑖 ∉ 𝜕 (𝑒 𝑗 ). Fix 𝑁 := 𝑝𝑞. For two hypergraphs 𝐻1 , 𝐻2 on (𝑉, 𝐸) with incidence matrices 𝑀 (𝐻1 ) = (𝑚 𝑖(1) 𝑗 ) and 𝑀 (𝐻2 ) = (𝑚 𝑖(2) 𝑗 ), define the hypergraph distance and similarity by 𝑝 𝑑 𝐻 (𝐻1 , 𝐻2 ) := 𝑞 1 ∑︁ ∑︁ (1) 𝑚 − 𝑚 𝑖(2) 𝑗 , 𝑁 𝑖=1 𝑗=1 𝑖 𝑗 𝑠 𝐻 (𝐻1 , 𝐻2 ) := 1 − 𝑑 𝐻 (𝐻1 , 𝐻2 ). Then 𝑑 𝐻 is a metric on the set of all hypergraphs on (𝑉, 𝐸), and 𝑠 𝐻 takes values in [0, 1]. 33

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Chapter 3. Basic Definition for SuperHyperGraph Definition 3.5.2 (Similarity and metric on 𝑛-SuperHyperGraphs). Fix a finite base set 𝑉0 and 𝑛 ∈ N0 . Let 𝑉 ⊆ P 𝑛 (𝑉0 ) and 𝐸 be finite sets, and let 𝜕 : 𝐸 → P∗ (𝑉) be an incidence map. Then (𝑉, 𝐸, 𝜕) is an 𝑛-SuperHyperGraph. Label 𝑉 = {𝑣 1 , . . . , 𝑣 𝑝 } and 𝐸 = {𝑒 1 , . . . , 𝑒 𝑞 } and define the incidence matrix 𝑀 (SHG (𝑛) ) = (𝑎 𝑖 𝑗 ) by ( 1, 𝑣 𝑖 ∈ 𝜕 (𝑒 𝑗 ), 𝑎 𝑖 𝑗 := 0, 𝑣 𝑖 ∉ 𝜕 (𝑒 𝑗 ). For two 𝑛-SuperHyperGraphs G1 , G2 on the same indexed sets (𝑉, 𝐸) with incidence matrices 𝑀 (G1 ) = (𝑎 𝑖(1) 𝑗 ) and 𝑀 (G2 ) = (𝑎 𝑖(2) 𝑗 ), put 𝑁 := 𝑝𝑞 and define 𝑝 (𝑛) 𝑑SH (G1 , G2 ) := 𝑞 1 ∑︁ ∑︁ (1) 𝑎 − 𝑎 𝑖(2) 𝑗 , 𝑁 𝑖=1 𝑗=1 𝑖 𝑗 (𝑛) (𝑛) 𝑠SH (G1 , G2 ) := 1 − 𝑑SH (G1 , G2 ). (𝑛) (𝑛) Then 𝑑SH is a metric on the set of all 𝑛-SuperHyperGraphs on (𝑉, 𝐸), and 𝑠SH ∈ [0, 1]. For reference, an overview of the comparison between Similarity and Metric on HyperGraphs and on SuperHyperGraphs is presented in Table 3.3. Table 3.3: Comparison of Similarity and Metric on HyperGraphs and on SuperHyperGraphs Aspect Similarity / Metric on HyperGraphs Similarity / Metric on SuperHyperGraphs Underlying structure Simple hypergraph 𝐻 = (𝑉, 𝐸) with incidence map 𝜕 : 𝐸 → P∗ (𝑉). Incidence matrix 𝑀 (𝐻) = (𝑚 𝑖 𝑗 ) with 𝑚 𝑖 𝑗 = 1 if 𝑣 𝑖 ∈ 𝜕 (𝑒 𝑗 ), and 0 otherwise. 𝑛-SuperHyperGraph (𝑉, 𝐸, 𝜕) with 𝑉 ⊆ P 𝑛 (𝑉0 ) and 𝜕 : 𝐸 → P∗ (𝑉). Incidence representation Distance Normalized Hamming distance on incidence matrices: 𝑑 𝐻 (𝐻1 , 𝐻2 ) = (2) (1) 1 Í 𝑖, 𝑗 |𝑚 𝑖 𝑗 − 𝑚 𝑖 𝑗 |, a metric on 𝑝𝑞 all hypergraphs on (𝑉, 𝐸). Similarity Similarity score 𝑠 𝐻 (𝐻1 , 𝐻2 ) = 1 − 𝑑 𝐻 (𝐻1 , 𝐻2 ) ∈ [0, 1]. Generalization Defined on a single-level hypergraph structure. Incidence matrix 𝑀 (G (𝑛) ) = (𝑎 𝑖 𝑗 ) with 𝑎 𝑖 𝑗 = 1 if 𝑣 𝑖 ∈ 𝜕 (𝑒 𝑗 ), and 0 otherwise (same scheme, but vertices are 𝑛-supervertices). Same normalized Hamming (𝑛) distance: 𝑑SH (G1 , G2 ) = (1) (2) 1 Í − 𝑎 |, a metric |𝑎 𝑖, 𝑗 𝑖𝑗 𝑖𝑗 𝑝𝑞 on all 𝑛-SuperHyperGraphs on (𝑉, 𝐸). (𝑛) Similarity score 𝑠SH (G1 , G2 ) = 1− (𝑛) 𝑑SH (G1 , G2 ) ∈ [0, 1]. Extends the hypergraph case: when 𝑛 = 0, similarity and metric reduce exactly to 𝑠 𝐻 and 𝑑 𝐻 . For 𝑛 ≥ 1, they compare multi-level superincidence patterns of SuperHyperGraphs. The concrete example is presented as follows. Example 3.5.3 (Concrete distance and similarity of two 1-SuperHyperGraphs). Let the finite base set be 𝑉0 := {𝑎, 𝑏}, and take 𝑛 = 1, so 𝑃1 (𝑉0 ) = 𝑃(𝑉0 ). Set 𝑉 := {𝑎}, {𝑏} ⊆ 𝑃1 (𝑉0 ), 34 𝐸 := {𝑒 1 }.

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Chapter 3. Basic Definition for SuperHyperGraph Define two 1-SuperHyperGraphs on the same indexed sets (𝑉, 𝐸): G1(1) := (𝑉, 𝐸, 𝜕1 ), G2(1) := (𝑉, 𝐸, 𝜕2 ), 𝜕1 (𝑒 1 ) := {𝑎} , 𝜕2 (𝑒 1 ) := {𝑎}, {𝑏} . with incidences Index 𝑉 = {𝑣 1 , 𝑣 2 } := {𝑎}, {𝑏} , 𝐸 = {𝑒 1 }, so 𝑝 = 2, 𝑞 = 1, and 𝑁 = 𝑝𝑞 = 2. The incidence matrices are 1 1 (1) (1) 𝑀 (G1 ) = , 𝑀 (G2 ) = . 0 1 By definition, 2 (1) 𝑑SH (G1(1) , G2(1) ) = 1 1 1 1 ∑︁ ∑︁ (1) 𝑎 − 𝑎 𝑖(2) 𝑗 = 2 |1 − 1| + |0 − 1| = 2 , 𝑁 𝑖=1 𝑗=1 𝑖 𝑗 and hence the similarity is (1) (1) 𝑠SH (G1(1) , G2(1) ) = 1 − 𝑑SH (G1(1) , G2(1) ) = 1 − 1 1 = . 2 2 Thus these two 1-SuperHyperGraphs have distance 21 and similarity 12 . Theorem 3.5.4 (Generalization of hypergraph similarity and metric). Let 𝑉, 𝐸 be fixed finite sets and let 𝐻1 , 𝐻2 be two hypergraphs on (𝑉, 𝐸). Regard each 𝐻𝑟 as a 0-SuperHyperGraph G𝑟(0) := (𝑉, 𝐸, 𝜕𝑟 ), 𝑟 = 1, 2, with the same incidence map 𝜕𝑟 as 𝐻𝑟 . Then (0) 𝑑SH (G1(0) , G2(0) ) = 𝑑 𝐻 (𝐻1 , 𝐻2 ), (0) 𝑠SH (G1(0) , G2(0) ) = 𝑠 𝐻 (𝐻1 , 𝐻2 ). In particular, similarity and metric on 𝑛-SuperHyperGraphs extend those on hypergraphs, which are recovered as the special case 𝑛 = 0. Proof. For 𝑟 = 1, 2 the incidence matrix of 𝐻𝑟 and of G𝑟(0) have the same entries by definition: 𝑚 𝑖(𝑟𝑗 ) = 1 ⇐⇒ 𝑣 𝑖 ∈ 𝜕𝑟 (𝑒 𝑗 ) ⇐⇒ 𝑎 𝑖(𝑟𝑗 ) = 1. (0) (0) Hence 𝑀 (𝐻𝑟 ) = 𝑀 (G𝑟(0) ) for 𝑟 = 1, 2, and therefore the formulas defining 𝑑 𝐻 , 𝑠 𝐻 and 𝑑SH , 𝑠SH coincide term by term. This proves the equalities in the statement. □ 3.6 SuperHypergraph Morphism SuperHyperGraph morphism maps supervertices and superedges between superhypergraphs, preserving incidence structure across all tiers and connections in a structure-preserving way. This is obtained by applying the concept of graph morphisms [180, 181] and hypergraph morphisms [17, 182, 183] to the framework of SuperHyperGraphs. Definition 3.6.1 (Hypergraph morphism). [17] Let 𝐻 = (𝑉, 𝐸) and 𝐻 ′ = (𝑉 ′ , 𝐸 ′ ) be hypergraphs without repeated hyperedges. A map 𝑓 : 𝑉 −→ 𝑉 ′ is called a hypergraph morphism from 𝐻 to 𝐻 ′ if for every hyperedge 𝑒 ∈ 𝐸 the image 𝑓 [𝑒] := { 𝑓 (𝑣) | 𝑣 ∈ 𝑒 } is a hyperedge of 𝐻 ′ , i.e. 𝑓 [𝑒] ∈ 𝐸 ′ . 35

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Chapter 3. Basic Definition for SuperHyperGraph Definition 3.6.2 (SuperHypergraph morphism). Let H1 = (𝑉1 , 𝐸 1 , 𝜕1 ) and H2 = (𝑉2 , 𝐸 2 , 𝜕2 ) be SuperHyperGraphs, where 𝑉𝑖 is the (possibly tiered) supervertex set, 𝐸 𝑖 is the set of superedges, and 𝜕𝑖 : 𝐸 𝑖 −→ P∗ (𝑉𝑖 ) is the incidence map assigning to each superedge a nonempty set of supervertices, with P∗ (𝑉𝑖 ) := P (𝑉𝑖 ) \ {∅}. A SuperHyperGraph morphism 𝐹 : H1 −→ H2 is a pair 𝐹 = ( 𝑓 , 𝑔) consisting of 𝑓 : 𝑉1 −→ 𝑉2 , 𝑔 : 𝐸 1 −→ 𝐸 2 , such that the following compatibility condition holds for every 𝑒 ∈ 𝐸 1 : 𝜕2 𝑔(𝑒) = 𝑓# 𝜕1 (𝑒) , where 𝑓# : P (𝑉1 ) −→ P (𝑉2 ), 𝑓# (𝑋) := { 𝑓 (𝑣) | 𝑣 ∈ 𝑋 }, is the direct image map on subsets. Table 3.4 presents a comparison of Hypergraph morphisms and SuperHyperGraph morphisms. Table 3.4: Comparison of Hypergraph morphisms and SuperHyperGraph morphisms Aspect Hypergraph morphism SuperHyperGraph morphism Underlying objects Hypergraphs 𝐻 = (𝑉, 𝐸) and 𝐻 ′ = (𝑉 ′ , 𝐸 ′ ) without repeated hyperedges. Maps A single vertex map 𝑓 : 𝑉 → 𝑉 ′ . Incidence preservation For every 𝑒 ∈ 𝐸, the image 𝑓 [𝑒] = { 𝑓 (𝑣) | 𝑣 ∈ 𝑒} is required to be a hyperedge of 𝐻 ′ , i.e. 𝑓 [𝑒] ∈ 𝐸 ′ . Level of structure Preserves membership of vertices in hyperedges at a single level. Reduction Fundamental notion in classical hypergraph theory. SuperHyperGraphs H1 = (𝑉1 , 𝐸 1 , 𝜕1 ) and H2 = (𝑉2 , 𝐸 2 , 𝜕2 ), where vertices and edges may be tiered. A pair of maps 𝐹 = ( 𝑓 , 𝑔) with 𝑓 : 𝑉1 → 𝑉2 (on supervertices) and 𝑔 : 𝐸 1 → 𝐸 2 (on superedges). For every 𝑒 ∈ 𝐸 1, the incidence condition 𝜕2 𝑔(𝑒) = 𝑓# 𝜕1 (𝑒) must hold, where 𝑓# (𝑋) = { 𝑓 (𝑣) | 𝑣 ∈ 𝑋 }. Preserves membership of supervertices in superedges across possibly multi-level superstructures via a compatible pair ( 𝑓 , 𝑔). Extends the hypergraph case: when supervertices/edges collapse to ordinary vertices/edges, the notion reduces to a hypergraph morphism. Example 3.6.3 (A simple SuperHyperGraph morphism). Let H1 = (𝑉1 , 𝐸 1 , 𝜕1 ) and H2 = (𝑉2 , 𝐸 2 , 𝜕2 ) be SuperHyperGraphs defined by 𝑉1 := {𝑣 1 , 𝑣 2 , 𝑣 3 }, 𝐸 1 := {𝑒 1 }, 𝜕1 (𝑒 1 ) := {𝑣 1 , 𝑣 2 }, 𝑉2 := {𝑤 1 , 𝑤 2 }, 𝐸 2 := { 𝑓1 }, 𝜕2 ( 𝑓1 ) := {𝑤 1 , 𝑤 2 }. Define maps 𝑓 : 𝑉1 → 𝑉2 , 𝑓 (𝑣 1 ) := 𝑤 1 , 𝑓 (𝑣 2 ) := 𝑤 2 , 𝑓 (𝑣 3 ) := 𝑤 2 , 𝑔 : 𝐸1 → 𝐸2 , 𝑔(𝑒 1 ) := 𝑓1 . 36

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Chapter 3. Basic Definition for SuperHyperGraph The direct image of the incident set of 𝑒 1 is 𝑓# 𝜕1 (𝑒 1 ) = 𝑓# ({𝑣 1 , 𝑣 2 }) = { 𝑓 (𝑣 1 ), 𝑓 (𝑣 2 )} = {𝑤 1 , 𝑤 2 }. Hence 𝜕2 𝑔(𝑒 1 ) = 𝜕2 ( 𝑓1 ) = {𝑤 1 , 𝑤 2 } = 𝑓# 𝜕1 (𝑒 1 ) , so the pair 𝐹 = ( 𝑓 , 𝑔) is a SuperHyperGraph morphism 𝐹 : H1 −→ H2 . Theorem 3.6.4 (SuperHyperGraph morphisms generalize hypergraph morphisms). Let 𝐻 = (𝑉, 𝐸) and 𝐻 ′ = (𝑉 ′ , 𝐸 ′ ) be hypergraphs without repeated hyperedges, and regard them as SuperHyperGraphs via H = (𝑉, 𝐸, 𝜕), H ′ = (𝑉 ′ , 𝐸 ′ , 𝜕 ′ ), where 𝜕 (𝑒) = 𝑒 ⊆ 𝑉, 𝜕 ′ (𝑒 ′ ) = 𝑒 ′ ⊆ 𝑉 ′ (𝑒 ∈ 𝐸, 𝑒 ′ ∈ 𝐸 ′ ). Then a map 𝑓 : 𝑉 → 𝑉 ′ is a hypergraph morphism 𝐻 → 𝐻 ′ if and only if there exists a map 𝑔 : 𝐸 → 𝐸 ′ such that ( 𝑓 , 𝑔) is a SuperHyperGraph morphism H → H ′ in the sense of Definition 3.6.2. Proof. (⇒) Suppose 𝑓 : 𝑉 → 𝑉 ′ is a hypergraph morphism. For each 𝑒 ∈ 𝐸 the image 𝑓 [𝑒] = { 𝑓 (𝑣) | 𝑣 ∈ 𝑒} is a hyperedge of 𝐻 ′ , so 𝑓 [𝑒] ∈ 𝐸 ′ . Define 𝑔 : 𝐸 → 𝐸 ′ by 𝑔(𝑒) := 𝑓 [𝑒] ∈ 𝐸 ′ . Then, for every 𝑒 ∈ 𝐸, 𝜕 ′ 𝑔(𝑒) = 𝑔(𝑒) = 𝑓 [𝑒] = 𝑓# 𝜕 (𝑒) , because 𝜕 (𝑒) = 𝑒 and 𝜕 ′ (𝑔(𝑒)) = 𝑔(𝑒) by construction. Hence ( 𝑓 , 𝑔) satisfies the compatibility condition and is a SuperHyperGraph morphism. (⇐) Conversely, assume there exists 𝑔 : 𝐸 → 𝐸 ′ such that ( 𝑓 , 𝑔) is a SuperHyperGraph morphism. For each 𝑒 ∈ 𝐸 we then have 𝜕 ′ 𝑔(𝑒) = 𝑓# 𝜕 (𝑒) . Using 𝜕 (𝑒) = 𝑒 and 𝜕 ′ (𝑔(𝑒)) = 𝑔(𝑒), this becomes 𝑔(𝑒) = 𝑓# (𝑒) = { 𝑓 (𝑣) | 𝑣 ∈ 𝑒}. Thus 𝑓 [𝑒] = 𝑔(𝑒) ∈ 𝐸 ′ , so 𝑓 sends every hyperedge of 𝐻 to a hyperedge of 𝐻 ′ . Therefore 𝑓 is a hypergraph morphism. Consequently, hypergraph morphisms are precisely those vertex maps that admit a completion to a SuperHyperGraph morphism between the associated SuperHyperGraphs, so the notion of SuperHyperGraph morphism is a genuine generalization of hypergraph morphism. □ 3.7 SuperHyperGraph Partitioning Graph partitioning divides a graph’s vertices into disjoint blocks, minimizing the number (or weight) of edges crossing between different blocks [184]. Related concepts such as Fuzzy Graph Partitioning [185, 186] and Directed Graph Partitioning [187–189] are also well known. Graph partitioning is essential for scalable computation, reducing communication costs, enabling parallelism, improving clustering quality, and accelerating large-scale optimization and learning. Hypergraph partitioning splits vertices into blocks, minimizing cut hyperedges while balancing block sizes, better capturing multiway relationships than standard graph partitioning [190–192]. SuperHyperGraph partitioning divides supervertices and superedges into balanced groups, minimizing cut weight while respecting hierarchical multi-level connectivity constraints and structure [193]. 37

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[beta]

Chapter 3. Basic Definition for SuperHyperGraph
Definition 3.7.1 (𝑘-way 𝑛-SuperHyperGraph partition). [193] Let 𝐻 (𝑛) = (𝑉, 𝐸) be an 𝑛-SuperHyperGraph,
and let 𝑘 ∈ N, 𝑘 ≥ 2. A 𝑘-way partition of 𝑉 is a family of subsets
V := {𝑉1 , . . . , 𝑉𝑘 }
such that
𝑉𝑖 ⊆ 𝑉,

𝑉𝑖 ∩ 𝑉 𝑗 = ∅ (𝑖 ≠ 𝑗),

𝑘
Ø

𝑉𝑖 = 𝑉 .

𝑖=1

Fix a balance parameter 𝑐 ≥ 1. The partition V is called 𝑐-balanced if
|𝑉 |
1 |𝑉 |
≤ |𝑉𝑖 | ≤ 𝑐
𝑐 𝑘
𝑘

for all 𝑖 = 1, . . . , 𝑘.

For a given partition V and a superedge 𝑒 ∈ 𝐸, define the number of parts spanned by 𝑒 as
span V (𝑒) := { 𝑖 ∈ {1, . . . , 𝑘 } | 𝑒 ∩ 𝑉𝑖 ≠ ∅ } .
The superedge-cut cost of V is
𝑓cut (V) :=

∑︁


span V (𝑒) − 1 .

𝑒∈𝐸

The 𝑘-way 𝑛-SuperHyperGraph partitioning problem is: given 𝐻 (𝑛) = (𝑉, 𝐸), 𝑘, and 𝑐 ≥ 1, find a 𝑐-balanced
𝑘-way partition V = {𝑉1 , . . . , 𝑉𝑘 } of 𝑉 that minimizes 𝑓cut (V) (or another chosen objective such as the sum
of external degrees).
Table 3.5 presents a Comparison of Graph, HyperGraph, and SuperHyperGraph Partitioning.
Table 3.5: Comparison of Graph, HyperGraph, and SuperHyperGraph Partitioning
Aspect

Graph Partitioning

HyperGraph Partitioning

SuperHyperGraph Partitioning

Underlying structure

Graph 𝐺 = (𝑉, 𝐸) with
edges joining two vertices.

HyperGraph 𝐻 = (𝑉, 𝐸)
with hyperedges 𝑒 ⊆ 𝑉.

Partition object

Vertex set 𝑉 split into disjoint blocks.
Number or total weight
of edges crossing between
blocks.

Vertex set 𝑉 split into disjoint blocks.
Number or total weight
of hyperedges incident to
more than one block.

𝑛-SuperHyperGraph
𝐻 (𝑛) = (𝑉, 𝐸) with supervertices and superedges
on iterated powersets.
Supervertex set 𝑉 split into
disjoint blocks.
Superedge-cut
cost
𝑓cut (V)
=
∑︁
(span V (𝑒)
− 1),

Cut notion

𝑒∈𝐸

Balance constraint

Block sizes approximately
equal (e.g., bounded ratio
to |𝑉 |/𝑘).

Block sizes approximately
equal under a chosen balance parameter.

Goal

Minimize edges crossing between blocks while
maintaining balance.

Minimize cut hyperedges (and possibly their
weights) while maintaining balance; better
captures multiway relationships.

Hereafter, we present a concrete example.
38

measuring how many
blocks each superedge
spans.
1 |𝑉 |
𝑐-balanced:
≤
𝑐 𝑘
|𝑉 |
|𝑉𝑖 | ≤ 𝑐
for all parts
𝑘
𝑉𝑖 .
Minimize superedge-cut
cost while respecting hierarchical, multi-level connectivity and structural
constraints.

#p274
#p39

40.

Chapter 3. Basic Definition for SuperHyperGraph Example 3.7.2 (2-way partition of a small 2-SuperHyperGraph). We give a concrete 2-SuperHyperGraph and an explicit optimal 2-way partition with respect to the cut objective. Base level (individuals). Let 𝑉0 := {𝑎, 𝑏, 𝑐, 𝑑} represent four individual employees. Level 1 (teams). Consider the following nonempty subsets of 𝑉0 : 𝑇1 := {𝑎, 𝑏}, 𝑇2 := {𝑏, 𝑐}, 𝑇3 := {𝑐, 𝑑}. Level 2 (departments as sets of teams). Define three departments 𝐷 1 := {𝑇1 , 𝑇2 }, 𝐷 2 := {𝑇2 , 𝑇3 }, 𝐷 3 := {𝑇1 , 𝑇3 }. Each 𝐷 𝑖 is a nonempty subset of {𝑇1 , 𝑇2 , 𝑇3 }, so 𝐷 𝑖 ∈ 𝑃 𝑃(𝑉0 ) = 𝑃2 (𝑉0 ). We set the 2-supervertex set and 2-superedge set as 𝑉 := {𝐷 1 , 𝐷 2 , 𝐷 3 }, n o 𝐸 := 𝑒 1 := {𝐷 1 , 𝐷 2 }, 𝑒 2 := {𝐷 2 , 𝐷 3 } . Then 𝐻 (2) = (𝑉, 𝐸) is a finite 2-SuperHyperGraph. We now partition 𝑉 into 𝑘 = 2 parts. Let 𝑉1 := {𝐷 1 , 𝐷 2 }, 𝑉2 := {𝐷 3 }. Clearly 𝑉1 ∩ 𝑉2 = ∅ and 𝑉1 ∪ 𝑉2 = 𝑉. Balance check. Here |𝑉 | = 3 and 𝑘 = 2, so the ideal size is |𝑉 |/𝑘 = 3/2. Choose 𝑐 = 2. Then 1 |𝑉 | 1 3 3 = · = , 𝑐 𝑘 2 2 4 We have |𝑉1 | = 2 and |𝑉2 | = 1, so 3 ≤ 1 ≤ 3, 4 hence the partition is 2-balanced. 𝑐 |𝑉 | 3 = 2 · = 3. 𝑘 2 3 ≤ 2 ≤ 3, 4 Cut cost. We compute span V (𝑒) for each superedge 𝑒 ∈ 𝐸, where V = {𝑉1 , 𝑉2 }. For 𝑒 1 = {𝐷 1 , 𝐷 2 } we have 𝑒 1 ⊆ 𝑉1 , so span V (𝑒 1 ) = 1, span V (𝑒 1 ) − 1 = 0. For 𝑒 2 = {𝐷 2 , 𝐷 3 } we have 𝐷 2 ∈ 𝑉1 and 𝐷 3 ∈ 𝑉2 , hence span V (𝑒 2 ) = 2, span V (𝑒 2 ) − 1 = 1. Therefore the total cut cost is 𝑓cut (V) = span V (𝑒 1 ) − 1 + span V (𝑒 2 ) − 1 = 0 + 1 = 1. If we instead consider the alternative partition 𝑉1′ := {𝐷 1 , 𝐷 3 }, 𝑉2′ := {𝐷 2 }, then both superedges span both parts: span V ′ (𝑒 1 ) = 2, span V ′ (𝑒 2 ) = 2, so 𝑓cut (V ′ ) = (2 − 1) + (2 − 1) = 2. Hence the original partition V = {𝑉1 , 𝑉2 } is strictly better with respect to the cut objective 𝑓cut . This example shows explicitly how a small 2-SuperHyperGraph can be partitioned into two balanced parts while minimizing the number of superedges that cross between parts. 39

41.

Chapter 3. Basic Definition for SuperHyperGraph 3.8 SuperHyperGraph Coloring Graph coloring assigns colors to vertices so adjacent vertices differ, modeling resource allocation, scheduling conflicts, or frequency assignment constraints [194–197]. Related concepts such as Fuzzy Graph Coloring [198, 199], Directed Graph Coloring [200–202], Edge Coloring [203, 204], Total coloring [205, 206], Face coloring [207, 208], and Neutrosophic Graph Coloring [194, 209] are also well known. HyperGraph coloring assigns colors to vertices so no hyperedge is monochromatic, extending classical coloring to multiway interactions and constraints [210–213]. SuperHyperGraph coloring assigns colors to supervertices across iterated powerset levels, preventing monochromatic superedges and capturing hierarchical multi-level conflict structures. Definition 3.8.1 (Hypergraph coloring). [214, 215] Let 𝐻 = (𝑉 (𝐻), 𝐸 (𝐻)) be a finite hypergraph with ∅ ≠ 𝑉 (𝐻), ∅ ≠ 𝐸 (𝐻) ⊆ P∗ 𝑉 (𝐻) , where P∗ (𝑋) := P (𝑋) \ {∅}. Let 𝑐 ∈ N with 𝑐 ≥ 1, and let C := {1, 2, . . . , 𝑐} be a set of 𝑐 colors. A 𝑐-coloring of 𝐻 is a function 𝜑 : 𝑉 (𝐻) −→ C. Such a coloring 𝜑 is called proper if no hyperedge is monochromatic, that is, ∀ 𝑒 ∈ 𝐸 (𝐻) : {𝜑(𝑣) | 𝑣 ∈ 𝑒} ≠ {𝑖} for every 𝑖 ∈ C. Equivalently, every 𝑒 ∈ 𝐸 (𝐻) contains at least two vertices with distinct colors. The chromatic number of 𝐻 is 𝜒(𝐻) := min 𝑐 ∈ N | 𝐻 admits a proper 𝑐-coloring . Definition 3.8.2 (SuperHyperGraph coloring). Let SHG (𝑛) = (𝑉𝑛 , 𝐸 𝑛 ) be an 𝑛-SuperHyperGraph as above. Fix 𝑐 ∈ N with 𝑐 ≥ 1 and a color set C := {1, 2, . . . , 𝑐}. A 𝑐-coloring of the 𝑛-SuperHyperGraph SHG (𝑛) is a function 𝜓 : 𝑉𝑛 −→ C. Such a coloring 𝜓 is called proper if no 𝑛-superedge is monochromatic, that is, ∀ 𝑒 ∈ 𝐸𝑛 : {𝜓(𝑣) | 𝑣 ∈ 𝑒} ≠ {𝑖} for every 𝑖 ∈ C. The SuperHyperGraph chromatic number of SHG (𝑛) is 𝜒 SHG (𝑛) := min 𝑐 ∈ N | SHG (𝑛) admits a proper 𝑐-coloring . Table 3.6 presents an overview of the comparison among Graph Coloring, HyperGraph Coloring, and SuperHyperGraph Coloring. Hereafter, we present a concrete example. 40

#p274
#p42

42.

[beta]

Chapter 3. Basic Definition for SuperHyperGraph
Table 3.6: Comparison of Graph Coloring, HyperGraph Coloring, and SuperHyperGraph Coloring
Aspect

Graph Coloring

HyperGraph Coloring

SuperHyperGraph Coloring

Underlying structure

Graph 𝐺 = (𝑉, 𝐸) with
edges joining pairs of vertices.
Vertices 𝑉 are colored.

HyperGraph 𝐻 = (𝑉, 𝐸)
with hyperedges 𝑒 ⊆ 𝑉.

Proper-coloring constraint

Adjacent vertices must receive different colors; no
edge is monochromatic.

No
hyperedge
is
monochromatic;
every hyperedge contains at
least two distinct colors.

Chromatic parameter

Chromatic number 𝜒(𝐺):
minimum number of colors in a proper coloring.

Chromatic number 𝜒(𝐻):
minimum number of colors in a proper hypergraph
coloring.

Level of conflict modeled

Pairwise conflicts between
individual vertices.

Multiway conflicts within
vertex subsets (hyperedges).

𝑛-SuperHyperGraph
SHG (𝑛) = (𝑉𝑛 , 𝐸 𝑛 ) on
iterated powersets.
Supervertices 𝑉𝑛 (collections on higher levels) are
colored.
No
𝑛-superedge
is
monochromatic;
every
superedge contains at least
two distinct colors at the
supervertex level.
SuperHyperGraph chromatic number 𝜒(SHG (𝑛) ):
minimum number of
colors in a proper
𝑛-SuperHyperGraph coloring.
Hierarchical multi-level
conflicts between supervertices and their
superedges.

Coloring object

Vertices 𝑉 are colored.

Example 3.8.3 (A 2-colorable SuperHyperGraph). Let
𝑉0 := {𝑣 1 , 𝑣 2 , 𝑣 3 },

𝐸 0 := {𝑒 1 , 𝑒 2 }

𝑒 1 := {𝑣 1 , 𝑣 2 },

𝑒 2 := {𝑣 2 , 𝑣 3 }.

with hyperedges
Then SHG (0) := (𝑉0 , 𝐸 0 ) is a 0-SuperHyperGraph.
Take 𝑐 = 2 and the color set
C := {1, 2}.
Define a coloring 𝜓 : 𝑉0 → C by
𝜓(𝑣 1 ) := 1,

𝜓(𝑣 2 ) := 2,

𝜓(𝑣 3 ) := 1.

For each 𝑒 ∈ 𝐸 0 we have
{𝜓(𝑣) | 𝑣 ∈ 𝑒 1 } = {𝜓(𝑣 1 ), 𝜓(𝑣 2 )} = {1, 2},
{𝜓(𝑣) | 𝑣 ∈ 𝑒 2 } = {𝜓(𝑣 2 ), 𝜓(𝑣 3 )} = {1, 2},
so no edge is monochromatic and 𝜓 is a proper 2-coloring.
If we tried 𝑐 = 1 and colored all vertices with a single color, then each edge would be monochromatic, so no
proper 1-coloring exists. Therefore

𝜒 SHG (0) = 2.
Example 3.8.4 (A 3-chromatic 1-SuperHyperGraph). Let the base set be
𝑉0 := {𝑎, 𝑏, 𝑐}.
Form three 1-supervertices
𝐴 := {𝑎, 𝑏},

𝐵 := {𝑏, 𝑐},
41

𝐶 := {𝑎, 𝑐},

43.

[beta]

Chapter 3. Basic Definition for SuperHyperGraph
and set
𝑉1 := {𝐴, 𝐵, 𝐶}.
Define 1-superedges
𝑒 1 := {𝐴, 𝐵},

𝑒 2 := {𝐵, 𝐶},

𝑒 3 := {𝐴, 𝐶},

and let
𝐸 1 := {𝑒 1 , 𝑒 2 , 𝑒 3 }.
(1)

Then SHG := (𝑉1 , 𝐸 1 ) is a 1-SuperHyperGraph whose underlying structure on the tier-1 vertices 𝐴, 𝐵, 𝐶 is
the complete graph 𝐾3 .
Take 𝑐 = 3 with color set
C := {1, 2, 3},
and define 𝜓 : 𝑉1 → C by
𝜓( 𝐴) := 1,

𝜓(𝐵) := 2,

𝜓(𝐶) := 3.

Then
{𝜓(𝑣) | 𝑣 ∈ 𝑒 1 } = {𝜓( 𝐴), 𝜓(𝐵)} = {1, 2},
{𝜓(𝑣) | 𝑣 ∈ 𝑒 2 } = {𝜓(𝐵), 𝜓(𝐶)} = {2, 3},
{𝜓(𝑣) | 𝑣 ∈ 𝑒 3 } = {𝜓( 𝐴), 𝜓(𝐶)} = {1, 3},
so no 1-superedge is monochromatic and 𝜓 is a proper 3-coloring.
On the other hand, any 2-coloring of 𝐴, 𝐵, 𝐶 must assign the same color to some pair, say 𝜓( 𝐴) = 𝜓(𝐵). Since
{𝐴, 𝐵} is a 1-superedge, this edge would then be monochromatic, contradicting properness. Hence no proper
2-coloring exists and

𝜒 SHG (1) = 3.
Theorem 3.8.5 (SuperHyperGraph coloring generalizes hypergraph coloring). Every hypergraph coloring
problem is a special case of SuperHyperGraph coloring at level 𝑛 = 0. More precisely, for every finite
hypergraph 𝐻 = (𝑉 (𝐻), 𝐸 (𝐻)) there exists a level-0 SuperHyperGraph
SHG (0) = (𝑉0 , 𝐸 0 )
such that:
1. 𝑉0 = 𝑉 (𝐻) and 𝐸 0 = 𝐸 (𝐻);
2. for every integer 𝑐 ≥ 1, the proper 𝑐-colorings of 𝐻 are exactly the proper 𝑐-colorings of SHG (0) (via
the same vertex-coloring functions);
3. in particular,
𝜒 𝐻


= 𝜒 SHG (0) .



Proof. Let 𝐻 = (𝑉 (𝐻), 𝐸 (𝐻)) be a finite hypergraph. Set
𝑉0 := 𝑉 (𝐻),

𝐸 0 := 𝐸 (𝐻).

Recall that by definition
P0 (𝑉0 ) = 𝑉0 ,

P∗ (𝑉0 ) = P (𝑉0 ) \ {∅}.


Since 𝐸 (𝐻) ⊆ P∗ 𝑉 (𝐻) = P∗ (𝑉0 ), the pair
SHG (0) := (𝑉0 , 𝐸 0 )
satisfies
∅ ≠ 𝐸 0 ⊆ P∗ (𝑉0 ),

∅ ≠ 𝑉0 ⊆ P0 (𝑉0 ),
so it is a level-0 SuperHyperGraph on the base set 𝑉0 .

Fix 𝑐 ∈ N, 𝑐 ≥ 1, and let C = {1, . . . , 𝑐} be the set of colors.
42

44.

Chapter 3. Basic Definition for SuperHyperGraph (1) Suppose first that 𝜑 : 𝑉 (𝐻) → C is a proper hypergraph 𝑐-coloring of 𝐻. Define 𝜓 : 𝑉0 −→ C, 𝜓(𝑣) := 𝜑(𝑣) (𝑣 ∈ 𝑉0 ). Since 𝑉0 = 𝑉 (𝐻) and 𝐸 0 = 𝐸 (𝐻), for every edge 𝑒 ∈ 𝐸 0 we have {𝜓(𝑣) | 𝑣 ∈ 𝑒} = {𝜑(𝑣) | 𝑣 ∈ 𝑒}. Because 𝜑 is proper on 𝐻, no 𝑒 ∈ 𝐸 (𝐻) = 𝐸 0 is monochromatic under 𝜑, hence no 𝑒 ∈ 𝐸 0 is monochromatic under 𝜓. Thus 𝜓 is a proper 𝑐-coloring of the level-0 SuperHyperGraph SHG (0) . (2) Conversely, suppose that 𝜓 : 𝑉0 → C is a proper 𝑐-coloring of SHG (0) . Define 𝜑 : 𝑉 (𝐻) −→ C, 𝜑(𝑣) := 𝜓(𝑣) (𝑣 ∈ 𝑉 (𝐻) = 𝑉0 ). For every hyperedge 𝑒 ∈ 𝐸 (𝐻) = 𝐸 0 we again have {𝜑(𝑣) | 𝑣 ∈ 𝑒} = {𝜓(𝑣) | 𝑣 ∈ 𝑒}. Since 𝜓 is proper on SHG (0) , no 𝑒 ∈ 𝐸 0 is monochromatic under 𝜓, hence no 𝑒 ∈ 𝐸 (𝐻) is monochromatic under 𝜑. Therefore 𝜑 is a proper 𝑐-coloring of the original hypergraph 𝐻. The constructions in (1) and (2) are inverses of each other (they are both the identity map on the underlying set 𝑉 (𝐻) = 𝑉0 ). Thus, for every 𝑐 ≥ 1, there is a natural bijection proper 𝑐-colorings of 𝐻 proper 𝑐-colorings of SHG (0) . Taking the minimum 𝑐 for which these sets are nonempty on each side, we obtain 𝜒(𝐻) = 𝜒 SHG (0) . Hence hypergraph coloring is realized exactly as the special case 𝑛 = 0 of SuperHyperGraph coloring, which proves that SuperHyperGraph coloring is a proper generalization of hypergraph coloring. □ 3.9 SuperHyperGraph Domination Graph domination investigates subsets of vertices such that every vertex either belongs to the subset or is adjacent to at least one vertex in it, with a primary focus on minimizing the size of such subsets in graphs [216–218]. Related notions of domination and its variants have also been extensively studied in the settings of fuzzy graphs and neutrosophic graphs (e.g., [219–222]). In addition, several well-known variants of domination exist, including secure domination [223, 224], paired domination [225, 226], double domination [227, 228], roman domination [229–231], connected domination [232–234], star domination [235–237], and total domination [238]. Hypergraph domination extends graph domination by requiring that each vertex outside a dominating set shares at least one hyperedge with a dominating vertex, thereby modeling influence coverage in more complex multiway interaction systems [239–242]. SuperHyperGraph domination further generalizes hypergraph domination to multi-tier supervertices, by requiring that every supervertex is connected, via at least one superedge, to some dominating supervertex while respecting the hierarchical structure across the superhypergraph levels. Definition 3.9.1 (Domination in a hypergraph). (cf. [239–241, 243]) Let 𝐻 = (𝑉, 𝐸) be a finite hypergraph with nonempty vertex set 𝑉 and hyperedge family 𝐸 ⊆ P∗ (𝑉) := P (𝑉) \ {∅}. A subset 𝐷 ⊆ 𝑉 is called a dominating set of 𝐻 if for every vertex 𝑣 ∈ 𝑉 \ 𝐷 there exists an edge 𝑒 ∈ 𝐸 such that 𝑣 ∈ 𝑒 and 𝑒 ∩ 𝐷 ≠ ∅. Equivalently, every vertex outside 𝐷 is contained in some edge that also contains at least one vertex of 𝐷. The domination number of 𝐻 is 𝛾(𝐻) := min{ |𝐷 | | 𝐷 ⊆ 𝑉 is a dominating set of 𝐻 }. 43

#p275

45.

Chapter 3. Basic Definition for SuperHyperGraph Example 3.9.2 (Domination in a small hypergraph). Consider the hypergraph 𝐻 = (𝑉, 𝐸) with vertex set 𝑉 := {1, 2, 3, 4} and hyperedge family 𝐸 := 𝑒 1 , 𝑒 2 , 𝑒 3 := {1, 2}, {2, 3}, {3, 4} . Define 𝐷 := {2, 3} ⊆ 𝑉 . We check that 𝐷 is a dominating set of 𝐻. For each vertex 𝑣 ∈ 𝑉 \ 𝐷 = {1, 4}: • 𝑣 = 1: we have 1 ∈ 𝑒 1 = {1, 2} and 𝑒 1 ∩ 𝐷 = {2} ≠ ∅. • 𝑣 = 4: we have 4 ∈ 𝑒 3 = {3, 4} and 𝑒 3 ∩ 𝐷 = {3} ≠ ∅. Thus every vertex outside 𝐷 lies in some hyperedge that also contains a vertex from 𝐷, so 𝐷 is dominating. No singleton {1}, {2}, {3}, or {4} is dominating: • {1} fails to dominate 4, • {2} fails to dominate 4, • {3} fails to dominate 1, • {4} fails to dominate 1. Hence no dominating set of size 1 exists, and the domination number is 𝛾(𝐻) = 2. Definition 3.9.3 (Domination in an 𝑛-SuperHyperGraph). (cf. [112]) Let SHG (𝑛) = (𝑉, 𝐸) be an 𝑛-SuperHyperGraph on a finite base set 𝑉0 . A subset 𝐷 ⊆ 𝑉 is called a dominating set of SHG (𝑛) if for every 𝑛-supervertex 𝑣 ∈ 𝑉 \ 𝐷 there exists an 𝑛-superedge 𝑒 ∈ 𝐸 such that 𝑣 ∈ 𝑒 and 𝑒 ∩ 𝐷 ≠ ∅. Equivalently, every 𝑛-supervertex outside 𝐷 lies in some 𝑛-superedge that also contains at least one 𝑛supervertex from 𝐷. The domination number of SHG (𝑛) is 𝛾 SHG (𝑛) := min{ |𝐷| | 𝐷 ⊆ 𝑉 is a dominating set of SHG (𝑛) }. Table 3.7 provides an overview of the comparison between graph, hypergraph, and superhypergraph domination. Hereafter, we present a concrete example. 44

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#p46

46.

[beta]

Chapter 3. Basic Definition for SuperHyperGraph
Table 3.7: Comparison of graph, hypergraph, and superhypergraph domination
Framework

Underlying structure

Domination condition

Graph domination

Vertices joined by ordinary edges; adjacency is pairwise between vertices.
Vertices joined by hyperedges; each
hyperedge is a nonempty subset of 𝑉.

A set 𝐷 ⊆ 𝑉 such that every 𝑣 ∈ 𝑉 \ 𝐷
is adjacent to at least one vertex in 𝐷.
A set 𝐷 ⊆ 𝑉 such that for every 𝑣 ∈
𝑉 \ 𝐷 there exists a hyperedge 𝑒 with
𝑣 ∈ 𝑒 and 𝑒 ∩ 𝐷 ≠ ∅.
A set 𝐷 ⊆ 𝑉 such that for every 𝑣 ∈
𝑉 \𝐷 there exists an 𝑛-superedge 𝑒 with
𝑣 ∈ 𝑒 and 𝑒 ∩ 𝐷 ≠ ∅, respecting the
hierarchical supervertex structure.

HyperGraph domination
SuperHyperGraph
domination

𝑛-supervertices 𝑉 ⊆ P 𝑛 (𝑉0 ) joined by
𝑛-superedges (images of the incidence
map).

Example 3.9.4 (Domination in a 1-SuperHyperGraph). Let the base set be
𝑉0 := {𝑎, 𝑏, 𝑐}.
Form three 1-supervertices
𝐴 := {𝑎, 𝑏},

𝐵 := {𝑏, 𝑐},

𝐶 := {𝑎, 𝑐},

and set
𝑉 := {𝐴, 𝐵, 𝐶}.
Define two 1-superedges
𝑒 1 := {𝐴, 𝐵},

𝑒 2 := {𝐵, 𝐶},

and let
𝐸 := {𝑒 1 , 𝑒 2 }.
Then
SHG (1) := (𝑉, 𝐸)
is a 1-SuperHyperGraph.
Consider the subset
𝐷 := {𝐵} ⊆ 𝑉 .
We verify that 𝐷 is a dominating set of SHG

(1)

.

For each 1-supervertex 𝑣 ∈ 𝑉 \ 𝐷 = {𝐴, 𝐶}:

• 𝑣 = 𝐴: we have 𝐴 ∈ 𝑒 1 = {𝐴, 𝐵} and 𝑒 1 ∩ 𝐷 = {𝐵} ≠ ∅.
• 𝑣 = 𝐶: we have 𝐶 ∈ 𝑒 2 = {𝐵, 𝐶} and 𝑒 2 ∩ 𝐷 = {𝐵} ≠ ∅.

Thus every 1-supervertex outside 𝐷 belongs to some 1-superedge that also contains an element of 𝐷, so 𝐷 is
dominating.
No dominating set of size 0 exists, so 𝐷 is a minimum dominating set and the domination number is

𝛾 SHG (1) = 1.
Theorem 3.9.5 (SuperHyperGraph domination generalizes hypergraph domination). Every finite hypergraph
can be viewed as a 0-SuperHyperGraph in such a way that dominating sets (and hence the domination number)
coincide. In particular, hypergraph domination is a special case of 𝑛-SuperHyperGraph domination (for
𝑛 = 0).
45

47.

Chapter 3. Basic Definition for SuperHyperGraph Proof. Let 𝐻 = (𝑉, 𝐸) be an arbitrary finite hypergraph with ∅ ≠ 𝑉 and ∅ ≠ 𝐸 ⊆ P∗ (𝑉). Take the base set 𝑉0 := 𝑉 and consider the 0-fold iterated powerset P 0 (𝑉0 ) = 𝑉0 . Define the 0-SuperHyperGraph (0) SHG 𝐻 := (𝑉 (0) , 𝐸 (0) ) by 𝑉 (0) := 𝑉, 𝐸 (0) := 𝐸 . Since 𝐸 (0) ⊆ P∗ (𝑉 (0) ) and 𝑉 (0) ⊆ P 0 (𝑉0 ), this is a valid 0-SuperHyperGraph on the base set 𝑉0 in the sense of the previous definition. We now compare dominating sets. Let 𝐷 ⊆ 𝑉. (i) Suppose 𝐷 is a dominating set of 𝐻. By definition of hypergraph domination, for every vertex 𝑣 ∈ 𝑉 \ 𝐷 there exists an edge 𝑒 ∈ 𝐸 such that 𝑣 ∈ 𝑒 and 𝑒 ∩ 𝐷 ≠ ∅. But 𝐸 (0) = 𝐸 and 𝑉 (0) = 𝑉, so the same condition reads: for every 𝑣 ∈ 𝑉 (0) \ 𝐷 there exists 𝑒 ∈ 𝐸 (0) with (0) 𝑣 ∈ 𝑒 and 𝑒 ∩ 𝐷 ≠ ∅. This is exactly the condition that 𝐷 is a dominating set of SHG 𝐻 . (0) (ii) Conversely, suppose 𝐷 ⊆ 𝑉 (0) = 𝑉 is a dominating set of SHG 𝐻 . By definition of 0-SuperHyperGraph domination, for every 𝑣 ∈ 𝑉 (0) \ 𝐷 there exists 𝑒 ∈ 𝐸 (0) such that 𝑣∈𝑒 and 𝑒 ∩ 𝐷 ≠ ∅. Since 𝐸 (0) = 𝐸, this is exactly the condition that 𝐷 is a dominating set of the original hypergraph 𝐻. Thus (0) }. { 𝐷 ⊆ 𝑉 | 𝐷 dominates 𝐻 } = { 𝐷 ⊆ 𝑉 (0) | 𝐷 dominates SHG 𝐻 Taking minima of the cardinalities of dominating sets on both sides, we obtain (0) 𝛾(𝐻) = 𝛾 SHG 𝐻 . Therefore every hypergraph domination problem can be regarded as a special case of 𝑛-SuperHyperGraph domination (with 𝑛 = 0), and SuperHyperGraph domination strictly generalizes hypergraph domination. □ 3.10 Sombor index of SuperHypergraphs Sombor index of a graph sums, over edges, the square root of squared endpoint degrees, capturing degree-based structural complexity information [244–246]. These concepts have been further extended and studied in various settings, including chemical graphs [247, 248], fuzzy graphs [249, 250], and neutrosophic graphs [251, 252]. Moreover, related concepts such as the modified Sombor index [253–255], the Zagreb index [256–258], the Hyper-Zagreb Index [259, 260], the ABC index [261, 262], and the GA index [263, 264] are also well known. Sombor index of a hypergraph generalizes this by summing square-rooted degree squares over each hyperedge’s incident vertices within complex interactions [265]. Sombor index of a superhypergraph extends further, aggregating degree-squared contributions over multi-tier superedges, reflecting hierarchical connectivity across nested structural levels. Definition 3.10.1 (Sombor index of a hypergraph). [265] Let 𝐻 = (𝑉, 𝐸) be a finite hypergraph, where 𝑉 is a nonempty finite vertex set and 𝐸 ⊆ P∗ (𝑉) is a finite family of nonempty subsets of 𝑉 (the hyperedges). For each vertex 𝑣 ∈ 𝑉, the degree of 𝑣 in 𝐻 is 𝑑 𝐻 (𝑣) := { 𝑒 ∈ 𝐸 | 𝑣 ∈ 𝑒 } . 46

#p275
#p276

48.

Chapter 3. Basic Definition for SuperHyperGraph The Sombor index of the hypergraph 𝐻 is defined by ∑︁ √︄ ∑︁ 𝑆𝑂 (𝐻) := 𝑑 𝐻 (𝑣) 2 . 𝑣 ∈𝑒 𝑒∈𝐸 When 𝐻 is 2-uniform (i.e., every hyperedge has size 2), this reduces to the classical Sombor index of a simple graph. Example 3.10.2 (Sombor index of a small hypergraph). Consider the hypergraph 𝐻 = (𝑉, 𝐸), where the vertex set and hyperedge family are 𝑉 := {𝑥, 𝑦, 𝑧}, 𝐸 := {𝑒 1 , 𝑒 2 , 𝑒 3 }, with 𝑒 1 := {𝑥, 𝑦}, 𝑒 2 := {𝑦, 𝑧}, 𝑒 3 := {𝑥, 𝑦, 𝑧}. This is a non–2-uniform hypergraph (since |𝑒 3 | = 3). Step 1: Vertex degrees. For each 𝑣 ∈ 𝑉, the degree 𝑑 𝐻 (𝑣) := |{𝑒 ∈ 𝐸 | 𝑣 ∈ 𝑒}| is: 𝑑 𝐻 (𝑥) = 2 (appears in 𝑒 1 , 𝑒 3 ), 𝑑 𝐻 (𝑦) = 3 (appears in 𝑒 1 , 𝑒 2 , 𝑒 3 ), 𝑑 𝐻 (𝑧) = 2 (appears in 𝑒 2 , 𝑒 3 ). Step 2: Sombor index. By definition, 𝑆𝑂 (𝐻) := ∑︁ √︄ ∑︁ 𝑑 𝐻 (𝑣) 2 . 𝑣 ∈𝑒 𝑒∈𝐸 We compute the contribution of each hyperedge. For 𝑒 1 = {𝑥, 𝑦}: ∑︁ 𝑑 𝐻 (𝑣) 2 = 𝑑 𝐻 (𝑥) 2 + 𝑑 𝐻 (𝑦) 2 = 22 + 32 = 4 + 9 = 13, 𝑣 ∈𝑒1 so the contribution of 𝑒 1 is √ 13. For 𝑒 2 = {𝑦, 𝑧}: ∑︁ 𝑑 𝐻 (𝑣) 2 = 𝑑 𝐻 (𝑦) 2 + 𝑑 𝐻 (𝑧) 2 = 32 + 22 = 9 + 4 = 13, 𝑣 ∈𝑒2 so the contribution of 𝑒 2 is also √ 13. For 𝑒 3 = {𝑥, 𝑦, 𝑧}: ∑︁ 𝑑 𝐻 (𝑣) 2 = 𝑑 𝐻 (𝑥) 2 + 𝑑 𝐻 (𝑦) 2 + 𝑑 𝐻 (𝑧) 2 = 22 + 32 + 22 = 4 + 9 + 4 = 17, 𝑣 ∈𝑒3 so the contribution of 𝑒 3 is √ 17. Therefore, the Sombor index of 𝐻 is √ √ √ √ √ 𝑆𝑂 (𝐻) = 13 + 13 + 17 = 2 13 + 17. In this example, the presence of a 3-vertex hyperedge 𝑒 3 shows how the Sombor index naturally extends beyond the graph (2-uniform) case. 47

49.

Chapter 3. Basic Definition for SuperHyperGraph Definition 3.10.3 (Degree in an 𝑛-SuperHyperGraph). Let SHG (𝑛) = (𝑉, 𝐸, 𝜕) be a level-𝑛 SuperHyperGraph. For each 𝑣 ∈ 𝑉, the degree of 𝑣 in SHG (𝑛) is 𝑑SHG (𝑛) (𝑣) := { 𝑒 ∈ 𝐸 | 𝑣 ∈ 𝜕 (𝑒) } . Definition 3.10.4 (Sombor index of an 𝑛-SuperHyperGraph). Let SHG (𝑛) = (𝑉, 𝐸, 𝜕) be a level-𝑛 SuperHyperGraph. The Sombor index of SHG (𝑛) is defined by ∑︁ √︄ ∑︁ (𝑛) 𝑆𝑂 SHG := 𝑑SHG (𝑛) (𝑣) 2 . 𝑒∈𝐸 𝑣 ∈𝜕(𝑒) Remark 3.10.5. If we view a hypergraph 𝐻 = (𝑉, 𝐸) in incidence form by taking 𝜕 (𝑒) = 𝑒 for all 𝑒 ∈ 𝐸, then the above formula coincides with the Sombor index of a hypergraph. Table 3.8 provides an overview of the comparison of the Sombor index for graphs, hypergraphs, and superhypergraphs. Table 3.8: Comparison of Sombor index for graphs, hypergraphs, and superhypergraphs Framework Underlying structure Graph Simple graph 𝐺 = (𝑉, 𝐸) with pairwise edges between vertices. Hypergraph SuperHypergraph Hypergraph 𝐻 = (𝑉, 𝐸) where each hyperedge 𝑒 ∈ 𝐸 is a nonempty subset of 𝑉. Level-𝑛 SuperHyperGraph SHG (𝑛) = (𝑉, 𝐸, 𝜕) with 𝑛-supervertices and 𝑛superedges. Sombor index ∑︁ √︁ 𝑆𝑂 (𝐺) = 𝑑𝐺 (𝑢) 2 + 𝑑𝐺 (𝑣) 2 . 𝑢𝑣 ∈𝐸 𝑆𝑂 (𝐻) = ∑︁ √︄∑︁ 𝑒∈𝐸 𝑆𝑂 SHG (𝑛) ∑︁ √︄ ∑︁ 𝑒∈𝐸 𝑑 𝐻 (𝑣) 2 . 𝑣 ∈𝑒 = 𝑑SHG (𝑛) (𝑣) 2 . 𝑣 ∈𝜕(𝑒) Example 3.10.6 (Sombor index of a 1-SuperHyperGraph with two tiers). We now consider a simple 1SuperHyperGraph that mixes base vertices and 1-supervertices. Step 1: Vertex sets and supervertices. Let the base set be 𝑉0 := {𝑎, 𝑏, 𝑐}. Form two first-tier (super)vertices 𝑃 := {𝑎, 𝑏}, 𝑄 := {𝑏, 𝑐}, and set 𝑉1 := {𝑃, 𝑄}. The total vertex set is 𝑉 := 𝑉0 ∪ 𝑉1 = {𝑎, 𝑏, 𝑐, 𝑃, 𝑄}. Step 2: Superedges and boundary map. Define three superedges 𝐸 := {𝑒 1 , 𝑒 2 , 𝑒 3 }, with boundary map 𝜕 : 𝐸 → P ∗ (𝑉) given by 𝜕 (𝑒 1 ) := {𝑎, 𝑃}, 𝜕 (𝑒 2 ) := {𝑏, 𝑃, 𝑄}, 𝜕 (𝑒 3 ) := {𝑐, 𝑄}. Thus SHG (1) := (𝑉, 𝐸, 𝜕) is a level-1 SuperHyperGraph: 𝑎, 𝑏, 𝑐 are base vertices, 𝑃, 𝑄 are 1-supervertices, and each superedge connects a small subset of these across tiers. 48

#p49

50.

Chapter 3. Basic Definition for SuperHyperGraph Step 3: Vertex degrees in SHG (1) . For 𝑣 ∈ 𝑉, the degree 𝑑SHG (1) (𝑣) := {𝑒 ∈ 𝐸 | 𝑣 ∈ 𝜕 (𝑒)} is: 𝑑SHG (1) (𝑎) = 1 (only in 𝜕 (𝑒 1 )), 𝑑SHG (1) (𝑏) = 1 (only in 𝜕 (𝑒 2 )), 𝑑SHG (1) (𝑐) = 1 (only in 𝜕 (𝑒 3 )), 𝑑SHG (1) (𝑃) = 2 (in 𝜕 (𝑒 1 ) and 𝜕 (𝑒 2 )), 𝑑SHG (1) (𝑄) = 2 (in 𝜕 (𝑒 2 ) and 𝜕 (𝑒 3 )). Step 4: Sombor index of the 1-SuperHyperGraph. By definition, ∑︁ √︄ ∑︁ 𝑑SHG (1) (𝑣) 2 . 𝑆𝑂 SHG (1) := 𝑣 ∈𝜕(𝑒) 𝑒∈𝐸 We compute each term. For 𝑒 1 with 𝜕 (𝑒 1 ) = {𝑎, 𝑃}: ∑︁ 𝑑SHG (1) (𝑣) 2 = 𝑑SHG (1) (𝑎) 2 + 𝑑SHG (1) (𝑃) 2 𝑣 ∈𝜕(𝑒1 ) = 12 + 22 = 1 + 4 = 5, so the contribution of 𝑒 1 is √ 5. For 𝑒 2 with 𝜕 (𝑒 2 ) = {𝑏, 𝑃, 𝑄}: ∑︁ 𝑑SHG (1) (𝑣) 2 = 𝑑SHG (1) (𝑏) 2 + 𝑑SHG (1) (𝑃) 2 + 𝑑SHG (1) (𝑄) 2 𝑣 ∈𝜕(𝑒2 ) = 12 + 22 + 22 = 1 + 4 + 4 = 9, so the contribution of 𝑒 2 is √ 9 = 3. For 𝑒 3 with 𝜕 (𝑒 3 ) = {𝑐, 𝑄}: ∑︁ 𝑑SHG (1) (𝑣) 2 = 𝑑SHG (1) (𝑐) 2 + 𝑑SHG (1) (𝑄) 2 𝑣 ∈𝜕(𝑒3 ) = 12 + 22 = 1 + 4 = 5, so the contribution of 𝑒 3 is √ 5. Therefore, the Sombor index of the 1-SuperHyperGraph is √ √ √ 𝑆𝑂 SHG (1) = 5 + 3 + 5 = 2 5 + 3. In this example, the Sombor index incorporates both base vertices (𝑎, 𝑏, 𝑐) and higher-tier supervertices (𝑃, 𝑄), reflecting how hierarchical incidences in a SuperHyperGraph contribute jointly to the overall index. 49

51.

[beta]

Chapter 3. Basic Definition for SuperHyperGraph
Theorem 3.10.7 (SuperHyperGraph Sombor index generalises the hypergraph Sombor index). Let 𝐻 = (𝑉, 𝐸)
be a finite hypergraph. Define the associated level-0 SuperHyperGraph
(0)
SHG 𝐻
:= (𝑉, 𝐸, 𝜕𝐻 ),

𝜕𝐻 (𝑒) := 𝑒

(𝑒 ∈ 𝐸).

Then
(0)
𝑆𝑂 SHG 𝐻



= 𝑆𝑂 (𝐻).

In particular, the Sombor index of an 𝑛-SuperHyperGraph is a strict extension of the Sombor index of a
hypergraph (the case 𝑛 = 0).
(0)
Proof. By construction, 𝑉 is the vertex set of both 𝐻 and SHG 𝐻
, and 𝐸 is the edge/superedge set in both
structures. For every vertex 𝑣 ∈ 𝑉 we have

𝑑SHG (0) (𝑣) = { 𝑒 ∈ 𝐸 | 𝑣 ∈ 𝜕𝐻 (𝑒) } = { 𝑒 ∈ 𝐸 | 𝑣 ∈ 𝑒 } = 𝑑 𝐻 (𝑣).
𝐻

(0)
Thus the degree of each vertex is identical in 𝐻 and in SHG 𝐻
.

Next, for every edge 𝑒 ∈ 𝐸 we have 𝜕𝐻 (𝑒) = 𝑒, so the inner sum in the SuperHyperGraph Sombor index is
∑︁
∑︁
𝑑SHG (0) (𝑣) 2 =
𝑑 𝐻 (𝑣) 2 .
𝐻

𝑣 ∈𝑒

𝑣 ∈𝜕𝐻 (𝑒)

Therefore
(0) 
𝑆𝑂 SHG 𝐻

=

∑︁ √︄
𝑒∈𝐸

∑︁

𝑑SHG

2
(0) (𝑣)

=

∑︁ √︄ ∑︁

𝐻

𝑣 ∈𝜕𝐻 (𝑒)

𝑒∈𝐸

𝑑 𝐻 (𝑣) 2 = 𝑆𝑂 (𝐻).

𝑣 ∈𝑒

Hence the Sombor index of an 𝑛-SuperHyperGraph extends the Sombor index of a hypergraph, and the latter
is recovered exactly when we restrict to level 𝑛 = 0 with 𝜕 (𝑒) = 𝑒.
□

3.11

SuperHyperGraph Labeling

Graph labeling assigns labels to a graph’s vertices and/or edges so that specified constraints hold, typically
driven by adjacency, incidence, or distances [266–268]. As related concepts in graph labeling, graceful
labeling [269, 270], magic labeling [271, 272], harmonious labeling [273, 274], and lucky labeling [275, 276]
are well known. Graph labeling has also been studied within the frameworks of fuzzy graphs, neutrosophic
graphs, and related generalized graph models (e.g., [277–280]).
Hypergraph labeling assigns labels to vertices and/or hyperedges so that incidence-based or overlap-based
constraints are satisfied across the hypergraph structure [281–283]. SuperHyperGraph labeling assigns labels
to 𝑛-supervertices and/or n-superedges so that constraints respect the super-incidence structure induced at
level 𝑛 [284]. SuperHyperGraph multilabeling assigns several label components to each supervertex and/or
superedge, requiring these components to satisfy coupled constraints and remain consistent [284].
Definition 3.11.1 (Graph Labeling). [266–268] Let 𝐺 = (𝑉, 𝐸) be a finite graph and let 𝐿 𝑉 and 𝐿 𝐸 be
nonempty label alphabets. A (possibly partial) graph labeling on 𝐺 consists of maps
ℓ𝑉 : 𝑉 → 𝐿 𝑉

and/or ℓ𝐸 : 𝐸 → 𝐿 𝐸 ,

where either map may be omitted if not used. A labeling schema is a predicate Φ(𝐺; ℓ𝑉 , ℓ𝐸 ) built from
adjacency/incidence in 𝐺, the graph distance dist𝐺 on 𝑉, and fixed relations/operations on the alphabets (e.g.
=, ≠, order, arithmetic, etc.). We call (ℓ𝑉 , ℓ𝐸 ) valid (for Φ) if Φ(𝐺; ℓ𝑉 , ℓ𝐸 ) holds.
Example 3.11.2 (An 𝐿 (2, 1) vertex-labeling on the path 𝑃5 ). Let 𝑃5 have vertices 𝑣 1 , 𝑣 2 , 𝑣 3 , 𝑣 4 , 𝑣 5 and edges
𝑣 𝑖 𝑣 𝑖+1 for 𝑖 = 1, 2, 3, 4. Let 𝐿 𝑉 = Z and define a vertex labeling ℓ𝑉 : 𝑉 (𝑃5 ) → Z by
ℓ𝑉 (𝑣 1 ) = 0, ℓ𝑉 (𝑣 2 ) = 2, ℓ𝑉 (𝑣 3 ) = 4, ℓ𝑉 (𝑣 4 ) = 1, ℓ𝑉 (𝑣 5 ) = 3.
50

#p276
#p277

52.

[beta]

Chapter 3. Basic Definition for SuperHyperGraph
Let Φ encode the 𝐿(2, 1) constraints:
dist 𝑃5 (𝑢, 𝑣) = 1 ⇒ |ℓ𝑉 (𝑢) − ℓ𝑉 (𝑣)| ≥ 2,

dist 𝑃5 (𝑢, 𝑣) = 2 ⇒ |ℓ𝑉 (𝑢) − ℓ𝑉 (𝑣)| ≥ 1.

Verification (distance 1):
|0 − 2| = 2, |2 − 4| = 2, |4 − 1| = 3, |1 − 3| = 2.
Verification (distance 2):
|0 − 4| = 4, |2 − 1| = 1, |4 − 3| = 1.
Hence Φ(𝑃5 ; ℓ𝑉 , ∅) holds, so ℓ𝑉 is a valid 𝐿(2, 1) graph labeling.
Definition 3.11.3 (HyperGraph Labeling). [281–283] Let 𝐻 = (𝑉, 𝐸) be a finite hypergraph with 𝐸 ⊆
P (𝑉) \ {∅}, and let 𝐿 𝑉 , 𝐿 𝐸 be nonempty alphabets. A (possibly partial) hypergraph labeling consists of maps
ℓ𝑉 : 𝑉 → 𝐿 𝑉

and/or ℓ𝐸 : 𝐸 → 𝐿 𝐸 .

Write 𝐺 (𝐻) for the primal (2-section) graph of 𝐻 on vertex set 𝑉, where {𝑢, 𝑣} is an edge of 𝐺 (𝐻) iff 𝑢 ≠ 𝑣 and
∃𝑒 ∈ 𝐸 with {𝑢, 𝑣} ⊆ 𝑒. Let dist 𝐻 denote the usual graph distance in 𝐺 (𝐻). A labeling schema is a predicate
Φ(𝐻; ℓ𝑉 , ℓ𝐸 ) built from the incidence relation 𝑣 ∈ 𝑒, the distance dist 𝐻 on 𝑉, and fixed relations/operations on
the alphabets. We call (ℓ𝑉 , ℓ𝐸 ) valid if Φ(𝐻; ℓ𝑉 , ℓ𝐸 ) holds.
Example 3.11.4 (Strong hyperedge coloring as a hypergraph labeling). Let 𝑉 = {1, 2, 3, 4} and let 𝐸 = {𝑒 1 , 𝑒 2 }
with
𝑒 1 = {1, 2, 3},
𝑒 2 = {3, 4}.
Take 𝐿 𝑉 = {𝑟, 𝑔, 𝑏} (colors) and define ℓ𝑉 by
ℓ𝑉 (1) = 𝑟,

ℓ𝑉 (2) = 𝑔,

ℓ𝑉 (3) = 𝑏,

ℓ𝑉 (4) = 𝑟.

Let Φ require strong hyperedge coloring: for every hyperedge 𝑒 ∈ 𝐸, the set {ℓ𝑉 (𝑣) : 𝑣 ∈ 𝑒} is pairwise
distinct. Then for 𝑒 1 we have {𝑟, 𝑔, 𝑏} (all distinct), and for 𝑒 2 we have {𝑏, 𝑟} (distinct). Hence Φ(𝐻; ℓ𝑉 , ∅)
holds, so ℓ𝑉 is a valid hypergraph labeling.
Definition 3.11.5 (SuperHyperGraph Labeling). [284] Fix 𝑛 ∈ N0 and a finite base set 𝑉0 . Write P 0 (𝑉0 ) = 𝑉0
and P 𝑘+1 (𝑉0 ) = P (P 𝑘 (𝑉0 )). An 𝑛-SuperHyperGraph is a pair SHG(𝑛) = (𝑉, 𝐸) where
𝑉 ⊆ P 𝑛 (𝑉0 ),

∅ ≠ 𝐸 ⊆ P (𝑉) \ {∅}.

Its primal (2-section) graph is 𝐺 (SHG(𝑛)) = (𝑉, 𝐸 ′ ) where {𝑋, 𝑌 } ∈ 𝐸 ′ iff 𝑋 ≠ 𝑌 and ∃𝐹 ∈ 𝐸 with
{𝑋, 𝑌 } ⊆ 𝐹. Let distSHG be the graph distance in 𝐺 (SHG(𝑛)).
Let 𝐿 𝑉 , 𝐿 𝐸 be nonempty alphabets. A (possibly partial) SuperHyperGraph labeling consists of maps
ℓ𝑉 : 𝑉 → 𝐿 𝑉

and/or ℓ𝐸 : 𝐸 → 𝐿 𝐸 .

A labeling schema is a predicate Φ(SHG(𝑛); ℓ𝑉 , ℓ𝐸 ) built from: the incidence relation 𝑋 ∈ 𝐹 (supervertex–
superedge), the distance distSHG on 𝑉, and the set-membership relations available inside P 𝑘 (𝑉0 ) for 0 ≤ 𝑘 ≤ 𝑛
(e.g. 𝑥 ∈ 𝑋 when 𝑋 ∈ P (𝑉0 )). We call (ℓ𝑉 , ℓ𝐸 ) valid if Φ(SHG(𝑛); ℓ𝑉 , ℓ𝐸 ) holds.
Example 3.11.6 (An 𝐿(2, 1) vertex-labeling on a level-𝑛 = 1 SuperHyperGraph). Let 𝑉0 = {𝑎, 𝑏, 𝑐, 𝑑} and
𝑛 = 1. Define supervertices (elements of P (𝑉0 )):
𝐴 = {𝑎, 𝑏},

𝐵 = {𝑏, 𝑐},

𝐶 = {𝑐, 𝑑},

𝐷 = {𝑎, 𝑑},

and let 𝑉 = {𝐴, 𝐵, 𝐶, 𝐷}. Define superedges (nonempty subsets of 𝑉):
𝐹1 = {𝐴, 𝐵, 𝐶},

𝐹2 = {𝐴, 𝐷},

and set SHG(1) = (𝑉, 𝐸) with 𝐸 = {𝐹1 , 𝐹2 }.
Take 𝐿 𝑉 = Z and define ℓ𝑉 : 𝑉 → Z by
ℓ𝑉 ( 𝐴) = 0,

ℓ𝑉 (𝐵) = 2,

ℓ𝑉 (𝐶) = 4,
51

ℓ𝑉 (𝐷) = 3.

#p276
#p277

53.

[beta]

Chapter 3. Basic Definition for SuperHyperGraph
Let Φ encode 𝐿 (2, 1) constraints using distSHG :
distSHG (𝑋, 𝑌 ) = 1 ⇒ |ℓ𝑉 (𝑋) − ℓ𝑉 (𝑌 )| ≥ 2,

distSHG (𝑋, 𝑌 ) = 2 ⇒ |ℓ𝑉 (𝑋) − ℓ𝑉 (𝑌 )| ≥ 1.

In the primal graph, 𝐴 is adjacent to 𝐵, 𝐶, 𝐷 and 𝐵 is adjacent to 𝐶 (via 𝐹1 ), so
|0 − 2| = 2, |0 − 4| = 4, |0 − 3| = 3, |2 − 4| = 2
for all distance-1 pairs, and
distSHG (𝐷, 𝐵) = 2, |3 − 2| = 1;

distSHG (𝐷, 𝐶) = 2, |3 − 4| = 1.

Hence Φ(SHG(1); ℓ𝑉 , ∅) holds, so ℓ𝑉 is a valid SuperHyperGraph labeling.
Definition 3.11.7 (SuperHyperGraph MultiLabeling). [284] Let SHG(𝑛) = (𝑉, 𝐸) be an 𝑛-SuperHyperGraph
over a base set 𝑉0 . Define the flattening (base support) maps ♭𝑛 : P 𝑛 (𝑉0 ) → P (𝑉0 ) recursively by
Ø
♭0 (𝑥) = 𝑥 (𝑥 ∈ 𝑉0 ),
♭ 𝑘+1 (𝑋) =
♭ 𝑘 (𝑌 ) (𝑋 ∈ P 𝑘+1 (𝑉0 )).
𝑌 ∈𝑋

Thus ♭𝑛 (𝑋) ⊆ 𝑉0 is the set of base elements that occur inside the 𝑛-level object 𝑋.
Fix nonnegative integers 𝑝, 𝑞 and choose nonempty alphabets
𝐿 𝑉(1) , . . . , 𝐿 𝑉( 𝑝) ,

𝐿 𝐸(1) , . . . , 𝐿 𝐸(𝑞) .

A SuperHyperGraph MultiLabeling on SHG(𝑛) consists of coordinate maps
ℓ𝑉(𝑎) : 𝑉 → 𝐿 𝑉(𝑎) (1 ≤ 𝑎 ≤ 𝑝),
ℓ𝐸(𝑏) : 𝐸 → 𝐿 𝐸(𝑏) (1 ≤ 𝑏 ≤ 𝑞),
Î
Î𝑝
equivalently ℓ𝑉 : 𝑉 → 𝑎=1
𝐿 𝑉(𝑎) and ℓ𝐸 : 𝐸 → 𝑞𝑏=1 𝐿 𝐸(𝑏) .
A multilabeling schema is a predicate Φ(SHG(𝑛); ℓ𝑉 , ℓ𝐸 ) built from the incidence relation 𝑋 ∈ 𝐹, the primal
distance distSHG on 𝑉, the membership relations inside P 𝑘 (𝑉0 ) (0 ≤ 𝑘 ≤ 𝑛), and the flattening operator ♭𝑛 (plus
fixed relations/operations on the alphabets). We call (ℓ𝑉 , ℓ𝐸 ) valid if Φ(SHG(𝑛); ℓ𝑉 , ℓ𝐸 ) holds.
Example 3.11.8 (A distance-aware ( 𝑝, 𝑞) = (2, 1) multilabel on a level-𝑛 = 1 SuperHyperGraph). Let
𝑉0 = {𝑎, 𝑏, 𝑐, 𝑑} and 𝑛 = 1. Define supervertices
𝑋1 = {𝑎, 𝑏},

𝑋2 = {𝑏, 𝑐},

𝑋3 = {𝑐, 𝑑},

set 𝑉 = {𝑋1 , 𝑋2 , 𝑋3 }, and define superedges
𝐹1 = {𝑋1 , 𝑋2 },

𝐹2 = {𝑋2 , 𝑋3 },

so SHG(1) = (𝑉, 𝐸) with 𝐸 = {𝐹1 , 𝐹2 }. In the primal graph we have distSHG (𝑋1 , 𝑋2 ) = 1, distSHG (𝑋2 , 𝑋3 ) = 1,
and distSHG (𝑋1 , 𝑋3 ) = 2.
Take alphabets 𝐿 𝑉(1) = Z, 𝐿 𝑉(2) = N, and 𝐿 𝐸(1) = N. Define the coordinate maps by
ℓ𝑉(1) (𝑋1 ) = 0, ℓ𝑉(1) (𝑋2 ) = 2, ℓ𝑉(1) (𝑋3 ) = 4,
ℓ𝑉(2) (𝑋1 ) = 2, ℓ𝑉(2) (𝑋2 ) = 2, ℓ𝑉(2) (𝑋3 ) = 2,
ℓ𝐸(1) (𝐹1 ) = 1,

ℓ𝐸(1) (𝐹2 ) = 1.

Let Φ require the following three constraints:
(L2,1)

distSHG (𝑋, 𝑌 ) = 1 ⇒ |ℓ𝑉(1) (𝑋) − ℓ𝑉(1) (𝑌 )| ≥ 2,
(Sup) ℓ𝑉(2) (𝑋) = |♭1 (𝑋)| for all 𝑋 ∈ 𝑉;

distSHG (𝑋, 𝑌 ) = 2 ⇒ |ℓ𝑉(1) (𝑋) − ℓ𝑉(1) (𝑌 )| ≥ 1;

(Int) ℓ𝐸(1) (𝐹) =

Ù

♭1 (𝑋) for all 𝐹 ∈ 𝐸 .

𝑋∈𝐹

Verification:
|ℓ𝑉(1) (𝑋1 ) − ℓ𝑉(1) (𝑋2 )| = |0 − 2| = 2,

|ℓ𝑉(1) (𝑋2 ) − ℓ𝑉(1) (𝑋3 )| = |2 − 4| = 2,

|0 − 4| = 4 (dist = 2),

and
♭1 (𝑋1 ) = {𝑎, 𝑏}, ♭1 (𝑋2 ) = {𝑏, 𝑐}, ♭1 (𝑋3 ) = {𝑐, 𝑑},
so |♭1 (𝑋𝑖 )| = 2 for all 𝑖, and
|♭1 (𝑋1 ) ∩ ♭1 (𝑋2 )| = |{𝑏}| = 1 = ℓ𝐸(1) (𝐹1 ),

|♭1 (𝑋2 ) ∩ ♭1 (𝑋3 )| = |{𝑐}| = 1 = ℓ𝐸(1) (𝐹2 ).

Hence Φ(SHG(1); ℓ𝑉 , ℓ𝐸 ) holds, so (ℓ𝑉 , ℓ𝐸 ) is a valid SuperHyperGraph MultiLabeling.
52

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54.

Chapter 3. Basic Definition for SuperHyperGraph 3.12 SuperHyperGraph Grammar A graph grammar rewrites labeled rank-two edges by replacement graphs, gluing two ordered attachment vertices, generating terminal graphs [285, 286]. Related concepts such as fuzzy graph grammars [287–289], digraph grammars [290,291], attributed graph grammars [292,293], and molecular graph grammars [294,295] are also known. A hypergraph grammar rewrites labeled hyperedges of arity r(A) by replacement hypergraphs, identifying ordered attachment tuples, generating terminals [296–298]. A superhypergraph grammar rewrites labeled superhyperedges by ranked n-superhypergraphs with port orderings, gluing external vertices, producing terminal superhypergraphs. Definition 3.12.1 (Ranked hypergraphs in ordered attachment form). Let Σ be a set of edge labels equipped with an arity map 𝑟 : Σ → N ≥1 . A ranked Σ-hypergraph is a tuple 𝐻 = (𝑉, 𝐸, lab, att) where 𝑉 is a finite vertex set, 𝐸 is a finite edge set, lab : 𝐸 → Σ, and att(𝑒) = (𝑣 1 , . . . , 𝑣 𝑟 (lab(𝑒) ) ) ∈ 𝑉 𝑟 (lab(𝑒) ) is the ordered attachment tuple of 𝑒. Definition 3.12.2 (Graph grammar (rank-2 hyperedge replacement)). Let Σ = 𝑁 ∪ 𝑇 be a disjoint union of nonterminals 𝑁 and terminals 𝑇, with arity map 𝑟 : Σ → N ≥1 satisfying 𝑟 (𝑎) = 2 for all 𝑎 ∈ Σ. A graph grammar (hyperedge-replacement, rank 2) is a tuple G𝐺 = (𝑁, 𝑇, 𝑆, 𝑃) where 𝑆 ∈ 𝑁 and each production is 𝐴 ⇒ 𝑅 with 𝐴 ∈ 𝑁 and 𝑅 a ranked Σ-hypergraph together with an ordered list of external vertices ext(𝑅) = (𝑢 1 , 𝑢 2 ) ∈ 𝑉 (𝑅) 2 . A derivation starts from the single-edge handle of 𝑆 and repeatedly replaces a nonterminal edge labeled 𝐴 by a fresh copy of 𝑅, identifying the two attachment vertices of the replaced edge with 𝑢 1 , 𝑢 2 , and deleting the replaced edge. The language 𝐿 (G𝐺 ) is the set of terminal graphs obtained. Definition 3.12.3 (Hypergraph grammar (hyperedge replacement)). Let Σ = 𝑁 ∪ 𝑇 be a disjoint union, with arity map 𝑟 : Σ → N ≥1 . A hypergraph grammar (hyperedge-replacement) is a tuple G𝐻 = (𝑁, 𝑇, 𝑆, 𝑃) where 𝑆 ∈ 𝑁 and each production is 𝐴 ⇒ 𝑅 with 𝐴 ∈ 𝑁 and 𝑅 a ranked Σ-hypergraph equipped with an ordered list of external vertices ext(𝑅) = (𝑢 1 , . . . , 𝑢𝑟 ( 𝐴) ) ∈ 𝑉 (𝑅) 𝑟 ( 𝐴) . A derivation starts from the single-edge handle of 𝑆 and repeatedly replaces a nonterminal edge 𝑒 labeled 𝐴 (with attachment tuple (𝑥1 , . . . , 𝑥𝑟 ( 𝐴) )) by a fresh copy of 𝑅, identifying 𝑢 𝑖 with 𝑥 𝑖 for all 𝑖, and deleting 𝑒. The language 𝐿(G𝐻 ) is the set of terminal hypergraphs obtained. Definition 3.12.4 (Ranked 𝑛-superhypergraphs with ports). Fix 𝑛 ∈ N0 , a base set 𝑉0 , a label set Σ and an arity map 𝑟 : Σ → N ≥1 . A ranked 𝑛-superhypergraph is a tuple S = (𝑉, 𝐸, lab, 𝜕, port) such that (𝑉, 𝐸, 𝜕) is an 𝑛-SuperHyperGraph over 𝑉0 , lab : 𝐸 → Σ, and for each 𝑒 ∈ 𝐸 we have a bijection (a port-ordering) port𝑒 : [𝑟 (lab(𝑒))] −−→ 𝜕 (𝑒). Equivalently, each edge has an ordered attachment tuple att(𝑒) = (port𝑒 (1), . . . , port𝑒 (𝑟 (lab(𝑒)))). Example 3.12.5 (A hypergraph grammar generating all finite loose paths (rank 2)). Let Σ = 𝑁 ∪ 𝑇 where 𝑁 = {𝐴} and 𝑇 = {𝑡}, and let the arity map be 𝑟 ( 𝐴) = 2, 𝑟 (𝑡) = 2. 53

#p277

55.

[beta]

Chapter 3. Basic Definition for SuperHyperGraph
We define a hyperedge-replacement hypergraph grammar
G𝐻 = (𝑁, 𝑇, 𝑆, 𝑃)

with

𝑆 := 𝐴.

Intuitively, terminals 𝑡 will form a loose path of 2-edges (i.e., an ordinary path graph seen as a 2-uniform
hypergraph). A derivation starts from the handle consisting of one nonterminal edge labeled 𝐴.
Define two productions (both of rank 2):
(1) Stop (produce one terminal edge).
𝐴 ⇒ 𝑅stop ,
where 𝑅stop is the ranked hypergraph with vertex set
𝑉 (𝑅stop ) = {𝑢 1 , 𝑢 2 },
edge set
𝐸 (𝑅stop ) = {𝑒},
label lab(𝑒) = 𝑡, attachment att(𝑒) = (𝑢 1 , 𝑢 2 ), and externals
ext(𝑅stop ) = (𝑢 1 , 𝑢 2 ).
(2) Extend (add one terminal edge and keep one nonterminal for further growth).
𝐴 ⇒ 𝑅ext ,
where 𝑅ext has vertex set
𝑉 (𝑅ext ) = {𝑢 1 , 𝑢 2 , 𝑤},
edge set
𝐸 (𝑅ext ) = {𝑒 1 , 𝑒 2 },
labels
lab(𝑒 1 ) = 𝑡,

lab(𝑒 2 ) = 𝐴,

attachments
att(𝑒 1 ) = (𝑢 1 , 𝑤),

att(𝑒 2 ) = (𝑤, 𝑢 2 ),

and externals
ext(𝑅ext ) = (𝑢 1 , 𝑢 2 ).
Then 𝐿 (G𝐻 ) is exactly the set of finite loose paths: each derivation applies 𝑅ext some number of times and
finally applies 𝑅stop , yielding a terminal 2-uniform hypergraph whose hyperedges form a path.
Definition 3.12.6 (𝑛-SuperHyperGraph grammar (superhyperedge replacement)). Let 𝑛 ∈ N0 , let Σ = 𝑁 ∪ 𝑇
be a disjoint union with arity map 𝑟, and fix a base set 𝑉0 . An 𝑛-superhypergraph grammar is a tuple
G𝑆(𝑛) = (𝑁, 𝑇, 𝑆, 𝑃; 𝑉0 )
where 𝑆 ∈ 𝑁 and each production is 𝐴 ⇒ 𝑅 with 𝐴 ∈ 𝑁 and
𝑅 = (𝑉𝑅 , 𝐸 𝑅 , lab𝑅 , 𝜕𝑅 , port 𝑅 )
a ranked 𝑛-superhypergraph together with an ordered list of external vertices
ext(𝑅) = (𝑢 1 , . . . , 𝑢𝑟 ( 𝐴) ) ∈ 𝑉𝑅𝑟 ( 𝐴) .
A derivation starts from the single-edge handle of 𝑆 (as a ranked 𝑛-superhypergraph) and repeatedly: choose
a nonterminal edge 𝑒 labeled 𝐴 with ordered attachment tuple (𝑥1 , . . . , 𝑥𝑟 ( 𝐴) ), take a fresh copy of 𝑅, identify
𝑢 𝑖 with 𝑥𝑖 for all 𝑖 ∈ [𝑟 ( 𝐴)], and delete 𝑒. The language 𝐿 (G𝑆(𝑛) ) is the set of terminal 𝑛-superhypergraphs
obtained.
54

56.

[beta]

Chapter 3. Basic Definition for SuperHyperGraph
Example 3.12.7 (A 2-SuperHyperGraph grammar generating a chain of supervertices (rank 2)). Fix a base set
𝑉0 := {𝑎, 𝑏, 𝑐},

𝑛 = 2.

Define the level-2 supervertex set (each element is a subset of P (𝑉0 ), hence lies in P 2 (𝑉0 ))
𝑝 𝑎 := {𝑎},
𝑣 𝐿 := {𝑝 𝑎 },

𝑣 𝑀 := {𝑝 𝑏 },

𝑝 𝑏 := {𝑏},

𝑝 𝑐 := {𝑐},
𝑉 := {𝑣 𝐿 , 𝑣 𝑀 , 𝑣 𝑅 } ⊆ P 2 (𝑉0 ).

𝑣 𝑅 := {𝑝 𝑐 },

Let Σ = 𝑁 ∪ 𝑇 with 𝑁 = {𝐴}, 𝑇 = {𝑡}, and arities
𝑟 ( 𝐴) = 2,

𝑟 (𝑡) = 2.

G𝑆(2) = (𝑁, 𝑇, 𝑆, 𝑃; 𝑉0 )

with

We define a 2-superhypergraph grammar
𝑆 := 𝐴.

We specify two productions 𝐴 ⇒ 𝑅stop and 𝐴 ⇒ 𝑅ext . In both, the external list has length 2 and the port maps
impose an order on each (super)edge incidence set.
(1) Stop. Let 𝑅stop = (𝑉𝑅 , 𝐸 𝑅 , lab𝑅 , 𝜕𝑅 , port 𝑅 ) where
𝑉𝑅 = {𝑣 𝐿 , 𝑣 𝑅 },
𝜕𝑅 (𝑒) = {𝑣 𝐿 , 𝑣 𝑅 },

𝐸 𝑅 = {𝑒},

lab𝑅 (𝑒) = 𝑡,

port𝑒𝑅 (1) = 𝑣 𝐿 , port𝑒𝑅 (2) = 𝑣 𝑅 ,

and
ext(𝑅stop ) = (𝑣 𝐿 , 𝑣 𝑅 ).
Thus 𝑅stop produces one terminal superedge connecting the two external supervertices.
(2) Extend. Let 𝑅ext = (𝑉𝑅 , 𝐸 𝑅 , lab𝑅 , 𝜕𝑅 , port 𝑅 ) where
𝑉𝑅 = {𝑣 𝐿 , 𝑣 𝑀 , 𝑣 𝑅 },

𝐸 𝑅 = {𝑒 1 , 𝑒 2 },

𝜕𝑅 (𝑒 1 ) = {𝑣 𝐿 , 𝑣 𝑀 },

lab𝑅 (𝑒 1 ) = 𝑡, lab𝑅 (𝑒 2 ) = 𝐴,

𝜕𝑅 (𝑒 2 ) = {𝑣 𝑀 , 𝑣 𝑅 },

port𝑒𝑅1 (1) = 𝑣 𝐿 , port𝑒𝑅1 (2) = 𝑣 𝑀 ,

port𝑒𝑅2 (1) = 𝑣 𝑀 , port𝑒𝑅2 (2) = 𝑣 𝑅 ,

and
ext(𝑅ext ) = (𝑣 𝐿 , 𝑣 𝑅 ).
Starting from the single-edge handle of 𝑆 = 𝐴, repeated application of 𝑅ext inserts a new intermediate
supervertex (a fresh copy of 𝑣 𝑀 ) and a terminal superedge to its left, while keeping a nonterminal superedge
to the right. A final application of 𝑅stop terminates the derivation. Hence 𝐿(G𝑆(2) ) consists of terminal
2-superhypergraphs whose terminal superedges labeled 𝑡 form a (super)edge-chain between the two original
external supervertices.
Theorem 3.12.8 (𝑛-superhypergraph grammars generalize hypergraph grammars). Let G𝐻 = (𝑁, 𝑇, 𝑆, 𝑃) be
a hypergraph grammar over (Σ, 𝑟).
(i) For 𝑛 = 0, there exists a 0-superhypergraph grammar G𝑆(0) such that (up to the notational identification of
hypergraphs with 0-SuperHyperGraphs)
𝐿(G𝑆(0) ) = 𝐿(G𝐻 ).
(ii) More generally, for any 𝑛 ∈ N0 there exists an 𝑛-superhypergraph grammar G𝑆(𝑛) and an embedding 𝜄𝑛
from terminal hypergraphs to terminal 𝑛-superhypergraphs such that

𝐿 (G𝑆(𝑛) ) = 𝜄𝑛 𝐿(G𝐻 ) .
55

57.

Chapter 3. Basic Definition for SuperHyperGraph Proof. (i) View every ranked Σ-hypergraph 𝐻 = (𝑉, 𝐸, lab, att) as a ranked 0-superhypergraph S(𝐻) = (𝑉, 𝐸, lab, 𝜕, port) over base set 𝑉0 := 𝑉, defined by 𝜕 (𝑒) := {𝑣 1 , . . . , 𝑣 𝑟 (lab(𝑒) ) } if att(𝑒) = (𝑣 1 , . . . , 𝑣 𝑟 (lab(𝑒) ) ), and port𝑒 (𝑖) := 𝑣 𝑖 for each 𝑖. This is well-defined because 𝑉 ⊆ P 0 (𝑉0 ) = 𝑉0 and 𝜕 (𝑒) ∈ P∗ (𝑉). Now define G𝑆(0) to have the same 𝑁, 𝑇, 𝑆, 𝑃, but interpret every right-hand side 𝑅 of a rule 𝐴 ⇒ 𝑅 as S(𝑅) and keep the same external list. A single replacement step in G𝐻 replaces an edge with attachment tuple (𝑥1 , . . . , 𝑥𝑟 ( 𝐴) ) by gluing the external vertices (𝑢 1 , . . . , 𝑢𝑟 ( 𝐴) ) of 𝑅 onto that tuple. Because S(·) preserves the ordered attachment tuple via the port maps, the same gluing and deletion operation is exactly a replacement step in G𝑆(0) . Hence derivations correspond step-by-step, and terminal objects coincide (up to the identification above), so 𝐿(G𝑆(0) ) = 𝐿 (G𝐻 ). (ii) Fix 𝑛 ∈ N0 and define the 𝑛-fold singleton nesting map 𝑠 𝑛 : 𝑉0 → P 𝑛 (𝑉0 ) by 𝑠0 (𝑣) := 𝑣, 𝑠 𝑘+1 (𝑣) := {𝑠 𝑘 (𝑣)} (𝑘 ≥ 0). Given a ranked Σ-hypergraph 𝐻 = (𝑉, 𝐸, lab, att), define 𝜄𝑛 (𝐻) := 𝑉 ′ , 𝐸, lab, 𝜕 ′ , port′ where 𝑉 ′ := {𝑠 𝑛 (𝑣) : 𝑣 ∈ 𝑉 } ⊆ P 𝑛 (𝑉0 ) (choose 𝑉0 to contain all vertex names used), and for each edge 𝑒 with att(𝑒) = (𝑣 1 , . . . , 𝑣 𝑟 (lab(𝑒) ) ) set 𝜕 ′ (𝑒) := {𝑠 𝑛 (𝑣 1 ), . . . , 𝑠 𝑛 (𝑣 𝑟 (lab(𝑒) ) )}, port′𝑒 (𝑖) := 𝑠 𝑛 (𝑣 𝑖 ). Thus 𝜄𝑛 (𝐻) is a ranked 𝑛-superhypergraph and preserves attachment order. Construct G𝑆(𝑛) from G𝐻 by applying 𝜄𝑛 to every right-hand side 𝑅 of a production 𝐴 ⇒ 𝑅, and by applying 𝑠 𝑛 to the external vertex list: if ext(𝑅) = (𝑢 1 , . . . , 𝑢𝑟 ( 𝐴) ), set ext(𝜄𝑛 (𝑅)) = (𝑠 𝑛 (𝑢 1 ), . . . , 𝑠 𝑛 (𝑢𝑟 ( 𝐴) )). Now check one-step rewriting: replacing a nonterminal edge 𝑒 in a sentential form identifies its attachment vertices (𝑥 1 , . . . , 𝑥𝑟 ( 𝐴) ) with the external vertices of the chosen rule. Since 𝜄𝑛 maps each attachment vertex 𝑥𝑖 to 𝑠 𝑛 (𝑥𝑖 ) and each external vertex 𝑢 𝑖 to 𝑠 𝑛 (𝑢 𝑖 ), the identifications commute with 𝜄𝑛 : 𝑠 𝑛 (𝑢 𝑖 ) identified with 𝑠 𝑛 (𝑥𝑖 ) ⇐⇒ 𝑢 𝑖 identified with 𝑥𝑖 . Therefore, applying a rule in G𝐻 and then embedding by 𝜄𝑛 yields the same result as first embedding the sentential form and then applying the corresponding rule in G𝑆(𝑛) . By induction on the length of derivations, terminal derivations correspond, and terminal languages satisfy 𝐿 (G𝑆(𝑛) ) = 𝜄𝑛 (𝐿(G𝐻 )). □ 56

58.

Chapter 4 Some Particular SuperHyperGraphs In graph theory and hypergraph theory, many graph classes have been studied extensively. Here, a graph class is a family of graphs defined by shared properties or constraints, typically closed under specified operations, which enables systematic analysis and the design of algorithms [299]. Studying graph classes reveals structural patterns, yields efficient algorithms for restricted inputs, clarifies complexity boundaries, and enables transferable theorems across graphs sharing forbidden substructures. In this chapter, we present the description and formulation of several particular types of SuperHyperGraphs. 4.1 Directed SuperHyperGraph As discussed above, graphs are widely applied across numerous domains. However, when modeling concepts that inherently involve directional information, the use of directed graphs becomes essential [300,301]. Several extensions of directed graphs are known, including fuzzy directed graphs [302], intuitionistic fuzzy directed graphs [303], rough directed graphs [304], soft directed graphs [305, 306], and neutrosophic directed graphs [307–309]. These structures have been further extended to directed hypergraphs [310–312] and directed superhypergraphs [73, 313, 314], which have attracted growing research interest. Definition 4.1.1 (Directed Hypergraph). (cf. [315, 316]) A directed hypergraph is a pair 𝐻 = (𝑉, 𝐸), where • 𝑉 is a finite set of vertices. • 𝐸 is a finite set of hyperarcs, each hyperarc 𝑒 ∈ 𝐸 being an ordered pair 𝑒 = 𝑇 (𝑒), 𝐻 (𝑒) ∈ P (𝑉) × P (𝑉), with 𝑇 (𝑒) ⊆ 𝑉, 𝑇 (𝑒) ≠ ∅, 𝐻 (𝑒) ⊆ 𝑉, 𝐻 (𝑒) ≠ ∅. Intuitively, each 𝑒 = (𝑇 (𝑒), 𝐻 (𝑒)) carries “flow” from all vertices in 𝑇 (𝑒) (the tail) to all vertices in 𝐻 (𝑒) (the head). Example 4.1.2 (A simple directed hypergraph: project dependency flow). Consider the finite vertex set 𝑉 := {Spec, Design, Implement, Test}, representing the phases of a software project: Specification, Design, Implementation, and Testing. Define the set of hyperarcs 𝐸 by 𝐸 := {𝑒 1 , 𝑒 2 }, 57

59.

Chapter 4. Some Particular SuperHyperGraphs where 𝑒 1 := 𝑇 (𝑒 1 ), 𝐻 (𝑒 1 ) := {Spec}, {Design, Implement} , 𝑒 2 := 𝑇 (𝑒 2 ), 𝐻 (𝑒 2 ) := {Design, Implement}, {Test} . Then 𝐻 := (𝑉, 𝐸) is a directed hypergraph in the sense of Definition 4.1.1. The hyperarc 𝑒 1 models that once the specification is completed, both Design and Implementation can start, while 𝑒 2 models that Testing starts only after both Design and Implementation are available. Definition 4.1.3 (Directed 𝑛-SuperHyperGraph). (cf. [2, 73]) Let 𝑆 be a nonempty base set and let 𝑛 ≥ 0 be an integer. Define iterated powersets by P 0 (𝑆) = 𝑆, P 𝑘+1 (𝑆) = P P 𝑘 (𝑆) (𝑘 ≥ 0). A directed 𝑛-SuperHyperGraph is a pair DSHG (𝑛) = (𝑉, 𝐸), where 𝑉 ⊆ P 𝑛 (𝑆), 𝐸 ⊆ P 𝑛 (𝑆) × P 𝑛 (𝑆), and each directed 𝑛-superedge 𝑒 ∈ 𝐸 is an ordered pair 𝑒 = Tail(𝑒), Head(𝑒) , Tail(𝑒), Head(𝑒) ⊆ P 𝑛 (𝑆), typically both nonempty. Such an 𝑒 carries “flow” from the entire set Tail(𝑒) of 𝑛-supervertices into Head(𝑒). Example 4.1.4 (A simple directed 1-SuperHyperGraph: information flow between groups). Let the base set of individuals be 𝑆 := {𝑢 1 , 𝑢 2 , 𝑢 3 , 𝑢 4 }, so that P 0 (𝑆) = 𝑆, P 1 (𝑆) = P (𝑆). We construct a directed 1-SuperHyperGraph, where each vertex is a group of individuals. Define the set of 1-supervertices 𝑉 := 𝐴 := {𝑢 1 , 𝑢 2 }, 𝐵 := {𝑢 2 , 𝑢 3 , 𝑢 4 }, 𝐶 := {𝑢 3 } ⊆ P 1 (𝑆), and the set of directed 1-superedges 𝐸 := {𝑒 1 , 𝑒 2 } ⊆ P 1 (𝑆) × P 1 (𝑆), where 𝑒 1 := Tail(𝑒 1 ), Head(𝑒 1 ) := {𝐴}, {𝐵} , 𝑒 2 := Tail(𝑒 2 ), Head(𝑒 2 ) := {𝐵}, {𝐶} . Then DSHG (1) := (𝑉, 𝐸) is a directed 1-SuperHyperGraph in the sense of Definition 4.1.3 with 𝑛 = 1. Here, 𝑒 1 represents information flowing from the group {𝑢 1 , 𝑢 2 } to the larger group {𝑢 2 , 𝑢 3 , 𝑢 4 }, and 𝑒 2 represents subsequent forwarding from {𝑢 2 , 𝑢 3 , 𝑢 4 } to the single individual {𝑢 3 }. For reference, Table 4.1 provides information comparing directed graphs, directed hypergraphs, and directed 𝑛-SuperHyperGraphs. 58

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Table 4.1: Comparison of directed graphs, directed hypergraphs, and directed 𝑛-SuperHyperGraphs
Framework

Vertices

Directed edge / arc structure

Directed graph

Finite vertex set 𝑉.

Directed hypergraph

Finite vertex set 𝑉.

Arc set 𝐴 ⊆ 𝑉 × 𝑉; each arc (𝑢, 𝑣) carries direction from 𝑢 (tail) to 𝑣 (head).
Hyperarc set 𝐸, each 𝑒 ∈ 𝐸 is
an ordered pair (𝑇 (𝑒), 𝐻 (𝑒)) with
nonempty 𝑇 (𝑒), 𝐻 (𝑒) ⊆ 𝑉; direction
flows from all 𝑇 (𝑒) to all 𝐻 (𝑒).
Directed 𝑛-superedge set 𝐸 ⊆ P 𝑛 (𝑆) ×
P 𝑛 (𝑆); each 𝑒 = (Tail(𝑒), Head(𝑒))
carries flow from a family of 𝑛supervertices to another, across hierarchical levels.

Directed
SuperHyperGraph

4.2

𝑛-

𝑛-supervertex set 𝑉 ⊆ P 𝑛 (𝑆) over a
base set 𝑆.

Bidirected SuperHyperGraph

One of the well-known extended notions of a directed graph is the bidirected graph. A bidirected graph assigns
to each vertex–edge incidence a sign indicating whether the edge is locally directed toward or away from
that vertex [317–320]. A bidirected hypergraph assigns such signs to vertex–hyperedge incidences, requiring
that the signed values on each hyperedge sum to zero [321]. A bidirected superhypergraph assigns signs to
supervertex–superedge incidences, again imposing that each superedge has total signed sum zero [5, 321].
Definition 4.2.1 (Bidirected Graph). [317] A bidirected graph (also called a bigraph) is a pair
𝐵 = (𝐺, 𝜏),
where 𝐺 = (𝑉, 𝐸) is a simple undirected graph (no loops and no parallel edges), and
𝜏 : 𝑉 × 𝐸 → {−1, 0, 1}
is a bidirection function such that for every vertex–edge pair (𝑣, 𝑒):
1. 𝜏(𝑣, 𝑒) = 1 means that the edge 𝑒 is locally directed towards 𝑣;
2. 𝜏(𝑣, 𝑒) = −1 means that the edge 𝑒 is locally directed away from 𝑣;
3. 𝜏(𝑣, 𝑒) = 0 means that 𝑣 is not incident to 𝑒.
The graph 𝐺 is called the underlying graph of 𝐵.
Example 4.2.2 (A concrete bidirected graph). Let
𝑉 = {𝑎, 𝑏, 𝑐},

𝐸 = {𝑒 1 , 𝑒 2 },

𝑒 1 = {𝑎, 𝑏}, 𝑒 2 = {𝑏, 𝑐}.

Define 𝜏 : 𝑉 × 𝐸 → {−1, 0, 1} by the table
𝜏(𝑣, 𝑒)
𝑣=𝑎
𝑣=𝑏
𝑣=𝑐

𝑒1
1
1
0

𝑒2
0
−1
1

Interpretation:
• On 𝑒 1 = {𝑎, 𝑏} we have 𝜏(𝑎, 𝑒 1 ) = 1 and 𝜏(𝑏, 𝑒 1 ) = 1, so 𝑒 1 is “towards” both 𝑎 and 𝑏.
• On 𝑒 2 = {𝑏, 𝑐} we have 𝜏(𝑏, 𝑒 2 ) = −1 (away from 𝑏) and 𝜏(𝑐, 𝑒 2 ) = 1 (towards 𝑐).
All other pairs (𝑣, 𝑒) have 𝜏(𝑣, 𝑒) = 0 exactly when 𝑣 ∉ 𝑒.
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Chapter 4. Some Particular SuperHyperGraphs Definition 4.2.3 (Bidirected Hypergraph). [321] A bidirected hypergraph is a triple 𝐻 = (𝑉, 𝐸, 𝜏), where 𝑉 is a nonempty set of vertices, 𝐸 is a family of nonempty subsets of 𝑉 (hyperedges), and 𝜏 : 𝑉 × 𝐸 → {−1, 0, 1} is a bidirection function satisfying: 𝜏(𝑣, 𝑒) = 0 ⇐⇒ 𝑣 ∉ 𝑒, and, additionally, for each hyperedge 𝑒 ∈ 𝐸 we impose the balancing condition ∑︁ 𝜏(𝑣, 𝑒) = 0. 𝑣 ∈𝑒 Example 4.2.4 (A concrete bidirected hypergraph). Let 𝑉 = {1, 2, 3, 4}, 𝐸 = {𝑒, 𝑓 }, 𝑒 = {1, 2, 3, 4}, 𝑓 = {2, 3}. Define 𝜏 : 𝑉 × 𝐸 → {−1, 0, 1} by 𝜏(1, 𝑒) = 1, 𝜏(2, 𝑒) = −1, 𝜏(3, 𝑒) = 1, 𝜏(4, 𝑒) = −1, and 𝜏(2, 𝑓 ) = 1, 𝜏(3, 𝑓 ) = −1, and 𝜏(𝑣, 𝑒 ′ ) = 0 whenever 𝑣 ∉ 𝑒 ′ . Verification of the balancing condition: ∑︁ 𝜏(𝑣, 𝑒) = 1 + (−1) + 1 + (−1) = 0, ∑︁ 𝑣 ∈𝑒 𝜏(𝑣, 𝑓 ) = 1 + (−1) = 0. 𝑣∈ 𝑓 Definition 4.2.5 (Bidirected Superhypergraph). [321] A bidirected superhypergraph is a quadruple H = (𝑉, 𝑆, 𝐸, 𝜏), where: 1. 𝑉 is a nonempty set of (base) vertices; 2. 𝑆 is a set of nonempty subsets of 𝑉, called supervertices; 3. 𝐸 is a family of superedges, where each 𝑒 ∈ 𝐸 is a nonempty subset of 𝑆; 4. 𝜏 : 𝑆 × 𝐸 → {−1, 0, 1} is a bidirection function such that 𝜏(𝑠, 𝑒) = 0 ⇐⇒ 𝑠 ∉ 𝑒, and for each superedge 𝑒 ∈ 𝐸 we impose the balancing condition ∑︁ 𝜏(𝑠, 𝑒) = 0. 𝑠∈𝑒 Example 4.2.6 (A concrete bidirected superhypergraph). Let the base vertex set be 𝑉 = {𝑎, 𝑏, 𝑐, 𝑑}. Define supervertices (nonempty subsets of 𝑉) by 𝑠1 = {𝑎, 𝑏}, 𝑠2 = {𝑏, 𝑐}, 𝑠3 = {𝑑}, 𝑠4 = {𝑎, 𝑑}, 𝑆 = {𝑠1 , 𝑠2 , 𝑠3 , 𝑠4 }. Define superedges by 𝐸 = {𝐸 1 , 𝐸 2 }, 𝐸 1 = {𝑠1 , 𝑠2 , 𝑠3 , 𝑠4 }, 60 𝐸 2 = {𝑠1 , 𝑠3 }.

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Framework
Bidirected graph

Objects
𝐵 = (𝐺, 𝜏), 𝐺 = (𝑉, 𝐸)

Bidirected hypergraph

𝐻 = (𝑉, 𝐸, 𝜏)

Bidirected SuperHyperGraph

H = (𝑉, 𝑆, 𝐸, 𝜏)

Incidence/sign rule (bidirection)
𝜏 : 𝑉 × 𝐸 → {−1, 0, 1}; 𝜏(𝑣, 𝑒) = 0 ⇔ 𝑣 ∉ 𝑒.
𝜏(𝑣, 𝑒) = 1 (towards 𝑣), −1 (away from 𝑣).
𝐸 ⊆ P (𝑉) \ {∅}; 𝜏 : 𝑉 × 𝐸 → {−1, 0, 1},
𝜏(𝑣, 𝑒)Í= 0 ⇔ 𝑣 ∉ 𝑒, and balance on each hyperedge: 𝑣 ∈𝑒 𝜏(𝑣, 𝑒) = 0.
𝑆 ⊆ P (𝑉) \ {∅} (supervertices), 𝐸 ⊆ P (𝑆) \ {∅}
(superedges); 𝜏 : 𝑆 × 𝐸 → {−1, 0, 1}, Í
𝜏(𝑠, 𝑒) = 0 ⇔
𝑠 ∉ 𝑒, and balance on each superedge: 𝑠∈𝑒 𝜏(𝑠, 𝑒) =
0.

Table 4.2: Concise overview of bidirected graphs, bidirected hypergraphs, and bidirected SuperHyperGraphs.
Define 𝜏 : 𝑆 × 𝐸 → {−1, 0, 1} by
𝜏(𝑠1 , 𝐸 1 ) = 1, 𝜏(𝑠2 , 𝐸 1 ) = −1, 𝜏(𝑠3 , 𝐸 1 ) = 1, 𝜏(𝑠4 , 𝐸 1 ) = −1,
𝜏(𝑠1 , 𝐸 2 ) = 1, 𝜏(𝑠3 , 𝐸 2 ) = −1,
and 𝜏(𝑠, 𝑒) = 0 whenever 𝑠 ∉ 𝑒.
Verification of the balancing condition:
∑︁
𝜏(𝑠, 𝐸 1 ) = 1 + (−1) + 1 + (−1) = 0,
𝑠∈𝐸1

∑︁

𝜏(𝑠, 𝐸 2 ) = 1 + (−1) = 0.

𝑠∈𝐸2

For reference, an overview of bidirected graphs, bidirected hypergraphs, and bidirected SuperHyperGraphs is
presented in Table 4.2.

4.3

Multidirected SuperHyperGraph

Multidirected graph is a directed graph that permits multiple parallel directed edges between the same ordered
pair of vertices, so edge multiplicity represents repeated or layered interactions [322, 323]. Multidirected
hypergraph is a directed hypergraph in which each hyperedge has a tail set and a head set (or head vertex), and
multiple identical directed hyperedges are allowed [314]. Multidirected SuperHyperGraph is a multidirected
hypergraph whose vertices are level- n supervertices (iterated-powerset objects), with directed superhyperedges
between supervertex sets and possible multiplicities [314].
Definition 4.3.1 (Multidirected Graph). [322, 323] A multidirected graph is a 5-tuple
𝐺 = (𝑉, 𝐸, 𝑠, 𝑡, 𝑚),
where 𝑉 is a finite set of vertices, 𝐸 is a finite set of directed edges (allowing repetitions), 𝑠 : 𝐸 → 𝑉 assigns
the source of each edge, 𝑡 : 𝐸 → 𝑉 assigns the target of each edge, and
𝑚 : 𝑉 × 𝑉 → N0
is a multiplicity function such that 𝑚(𝑢, 𝑣) counts how many edges are directed from 𝑢 to 𝑣.
Example 4.3.2 (Parallel Data Channels). Let 𝑉 = {𝐴, 𝐵, 𝐶} (three servers). Take directed edges
(1)
(2)
𝐸 = { 𝑓 𝐴𝐵
, 𝑓 𝐴𝐵
, 𝑓 𝐵𝐶 , 𝑓𝐶(1)𝐴 , 𝑓𝐶(2)𝐴 , 𝑓𝐶(3)𝐴 },

with



(𝑖)
𝑠 𝑓 𝐴𝐵
= 𝐴,



(𝑖)
𝑡 𝑓 𝐴𝐵
= 𝐵 (𝑖 = 1, 2),
𝑠( 𝑓 𝐵𝐶 ) = 𝐵, 𝑡 ( 𝑓 𝐵𝐶 ) = 𝐶,




( 𝑗)
( 𝑗)
𝑠 𝑓𝐶 𝐴 = 𝐶, 𝑡 𝑓𝐶 𝐴 = 𝐴 ( 𝑗 = 1, 2, 3).

Define 𝑚( 𝐴, 𝐵) = 2, 𝑚(𝐵, 𝐶) = 1, 𝑚(𝐶, 𝐴) = 3, and 𝑚(𝑢, 𝑣) = 0 otherwise. Then 𝐺 = (𝑉, 𝐸, 𝑠, 𝑡, 𝑚) models
the directed channels together with their parallel counts.
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Chapter 4. Some Particular SuperHyperGraphs
Type
Undirected graph
Directed graph (digraph)
Bidirected graph
Multidirected graph

Edge object
𝐸 ⊆ {{𝑢, 𝑣} : 𝑢, 𝑣 ∈ 𝑉 }
𝐴 ⊆ 𝑉 ×𝑉
𝐺 = (𝑉, 𝐸) with incidence
signs 𝜏 : 𝑉 × 𝐸 → {−1, 0, 1}
Parallel arcs allowed (multiplicity 𝑚(𝑢, 𝑣) ∈ N0 )

Keyword-style description
No orientation; adjacency is symmetric.
Arcs (𝑢, 𝑣); orientation from tail 𝑢 to head
𝑣.
Local direction at each incidence (𝑣, 𝑒);
each edge has two signed ends.
Multiple directed edges between the same
ordered pair; models repeated/layered
flow.

Table 4.3: Concise overview of undirected, directed, bidirected, and multidirected graphs.
For reference, Table 4.3 presents an overview of undirected, directed, bidirected, and multidirected graphs.
Definition 4.3.3 (Multidirected Hypergraph). [314] A multidirected hypergraph is a triple
𝐻 = (𝑉, 𝐸, 𝑚),
where 𝑉 is a finite vertex set, 𝐸 is a finite set of directed hyperedges, and 𝑚 : 𝐸 → N assigns a positive integer
multiplicity to each hyperedge. Each hyperedge 𝑒 ∈ 𝐸 is an ordered pair

𝑒 = 𝑇 (𝑒), ℎ(𝑒) ,
where 𝑇 (𝑒) ⊆ 𝑉 is a nonempty tail (a set of sources) and ℎ(𝑒) ∈ 𝑉 is a head (a single target). The value 𝑚(𝑒)
records how many parallel instances of 𝑒 occur.
Example 4.3.4 (Collaborative Report Workflow). Let 𝑉 = {Hiroko, Shinya, Masahiro, Tae}. Define two
hyperedges (collaborations sending drafts to a manager)


𝑒 1 = {Hiroko, Shinya}, Tae ,
𝑒 2 = {Shinya, Masahiro}, Tae ,
and set 𝑚(𝑒 1 ) = 2 (two distinct monthly drafts) and 𝑚(𝑒 2 ) = 3 (three distinct weekly drafts). Then 𝐻 =
(𝑉, {𝑒 1 , 𝑒 2 }, 𝑚) encodes directed group-to-individual submissions with multiplicities.
Definition 4.3.5 (Multidirected 𝑛-SuperHyperGraph (Multidirected Superhypergraph)). [314] Fix an integer
𝑛 ≥ 1 and a finite base set 𝑉0 . Define iterated powersets by P 0 (𝑉0 ) := 𝑉0 and P 𝑘+1 (𝑉0 ) := P (P 𝑘 (𝑉0 )). A
multidirected 𝑛-SuperHyperGraph is a triple
𝑆𝐻 = (𝑉, 𝐸, 𝑚),
where
𝑉 ⊆ P 𝑛 (𝑉0 )
is a set of 𝑛-supervertices, and
𝐸 ⊆ P (𝑉) × P (𝑉)
is a set of directed 𝑛-superhyperedges. Each 𝑒 ∈ 𝐸 is an ordered pair

𝑒 = 𝑇 (𝑒), 𝐻 (𝑒)
with nonempty tail 𝑇 (𝑒) ⊆ 𝑉 and nonempty head 𝐻 (𝑒) ⊆ 𝑉. Finally, 𝑚 : 𝐸 → N assigns a positive integer
multiplicity to each directed 𝑛-superhyperedge.
Example 4.3.6 (Committees and Councils). Let 𝑉0 = {Hiroko, Shinya, Tae, Masahiro}. Form three committees
in P 1 (𝑉0 ):
𝐶1 = {Hiroko, Shinya}, 𝐶2 = {Shinya, Tae}, 𝐶3 = {Tae, Masahiro}.
Create two councils (2-supervertices) in P 2 (𝑉0 ):
𝑣 𝐼 = {𝐶1 , 𝐶2 },

𝑣 𝐼 𝐼 = {𝐶2 , 𝐶3 },

𝑉 = {𝑣 𝐼 , 𝑣 𝐼 𝐼 } ⊆ P 2 (𝑉0 ).

Define directed 2-superhyperedges

𝑒 1 = {𝑣 𝐼 }, {𝑣 𝐼 𝐼 } ,


𝑒 2 = {𝑣 𝐼 , 𝑣 𝐼 𝐼 }, {𝑣 𝐼 } ,

with multiplicities 𝑚(𝑒 1 ) = 5 and 𝑚(𝑒 2 ) = 2. Then 𝑆𝐻 = (𝑉, {𝑒 1 , 𝑒 2 }, 𝑚) captures hierarchical groupings (as
supervertices) and repeated directed exchanges (as multiplicities).
For reference, an overview of multidirected graphs, multidirected hypergraphs, and multidirected 𝑛-SuperHyperGraphs
is presented in Table 4.4.
62

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Framework
Multidirected Graph

Vertices
Vertex set 𝑉

Multidirected
Graph

Vertex set 𝑉

Hyper-

Multidirected
SuperHyperGraph

𝑛-

𝑛-supervertex set 𝑉 ⊆ P 𝑛 (𝑉0 )
over a base set 𝑉0

(Multi)directed edge structure
Directed edges with multiplicity; parallel arcs
allowed between the same ordered pair (𝑢, 𝑣) ∈
𝑉 × 𝑉 (e.g. via a multiplicity map 𝑚(𝑢, 𝑣) ∈ N0 ).
Directed hyperedges with multiplicity; each hyperarc has a tail and head (e.g. 𝑒 = (𝑇 (𝑒), 𝐻 (𝑒))
with nonempty 𝑇 (𝑒), 𝐻 (𝑒) ⊆ 𝑉), and identical
hyperarcs may occur multiple times.
Directed 𝑛-superhyperedges with multiplicity; each 𝑒 = (𝑇 (𝑒), 𝐻 (𝑒)) has nonempty
𝑇 (𝑒), 𝐻 (𝑒) ⊆ 𝑉 (families of 𝑛-supervertices),
and parallel copies are recorded by 𝑚(𝑒) ∈ N.

Table 4.4: Concise overview of multidirected graphs, multidirected hypergraphs, and multidirected 𝑛SuperHyperGraphs.

4.4

Mixed SuperHyperGraph

A mixed graph is a graph on a single vertex set that allows both undirected edges and directed arcs simultaneously
[324, 325]. As related concepts, fuzzy mixed graphs [326–328] and neutrosophic mixed graphs [329] are also
well known. A mixed hypergraph is a hypergraph that permits both undirected hyperedges and directed
hyperedges (with tails and heads) in one model [314]. A mixed superhypergraph is a superhypergraph whose
supervertices are nested-set objects and whose superedges may be undirected or directed [5].
Definition 4.4.1 (Mixed Graph). [324, 325] A mixed graph is a pair
𝐺 = (𝑉, 𝐸 ∪ 𝐴),
where 𝑉 ≠ ∅ is a set of vertices, 𝐸 ⊆ {{𝑢, 𝑣} : 𝑢, 𝑣 ∈ 𝑉, 𝑢 ≠ 𝑣} is a set of undirected edges, and
𝐴 ⊆ {(𝑢, 𝑣) ∈ 𝑉 × 𝑉 : 𝑢 ≠ 𝑣} is a set of directed edges (arcs). Thus, a mixed graph may contain both
undirected and directed adjacencies.
Definition 4.4.2 (Mixed HyperGraph). [5] A mixed hypergraph is a pair
𝐻 = (𝑉, 𝐸 ∪ 𝐴),
where 𝑉 ≠ ∅ is a set of vertices, 𝐸 is a set of undirected hyperedges with
𝐸 ⊆ {𝑒 ⊆ 𝑉 : 𝑒 ≠ ∅, |𝑒| ≥ 2},
and 𝐴 is a set of directed hyperedges (dyperedges) of the form
𝐴 ⊆ {(𝑍, 𝑧) : 𝑍 ⊆ 𝑉 \ {𝑧}, 𝑍 ≠ ∅, 𝑧 ∈ 𝑉 }.
Here (𝑍, 𝑧) represents a directed relation from the tail set 𝑍 to the head vertex 𝑧.
Definition 4.4.3 (Mixed SuperHyperGraph). [5] A mixed superhypergraph (or mixed SuperHyperGraph) is a
quadruple
H = (𝑉, 𝑆, 𝐸, 𝐴),
where:
1. 𝑉 ≠ ∅ is a set of (base) vertices,
2. 𝑆 ⊆ P (𝑉) \ {∅} is a set of supervertices (each 𝑠 ∈ 𝑆 is a nonempty subset of 𝑉),
3. 𝐸 ⊆ P (𝑆) \ {∅} is a set of undirected superedges (each 𝑒 ∈ 𝐸 is a nonempty subset of 𝑆),
4. 𝐴 ⊆ {(𝑍, 𝑧) : 𝑍 ⊆ 𝑆 \ {𝑧}, 𝑍 ≠ ∅, 𝑧 ∈ 𝑆} is a set of directed superedges (or super-dyperedges), so (𝑍, 𝑧)
represents a directed relation from the tail supervertex-set 𝑍 to the head supervertex 𝑧.
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Chapter 4. Some Particular SuperHyperGraphs Example 4.4.4 (A small mixed SuperHyperGraph). Let the base vertex set be 𝑉 := {1, 2, 3, 4}. Define the supervertex set 𝑆 := {𝑠1 , 𝑠2 , 𝑠3 } ⊆ P (𝑉) \ {∅}, 𝑠1 := {1, 2}, 𝑠2 := {2, 3}, 𝑠3 := {4}. Define one undirected superedge 𝐸 := {𝑒 1 } ⊆ P (𝑆) \ {∅}, 𝑒 1 := {𝑠1 , 𝑠2 }. Define two directed superedges (super-dyperedges) 𝐴 := {(𝑍1 , 𝑧1 ), (𝑍2 , 𝑧2 )}, where (𝑍1 , 𝑧1 ) := ({𝑠1 }, 𝑠3 ), (𝑍2 , 𝑧2 ) := ({𝑠2 , 𝑠3 }, 𝑠1 ). Then H = (𝑉, 𝑆, 𝐸, 𝐴) is a mixed SuperHyperGraph in the sense of Definition (Mixed SuperHyperGraph): it contains an undirected superedge 𝑒 1 connecting 𝑠1 and 𝑠2 , and directed superedges {𝑠1 } → 𝑠3 and {𝑠2 , 𝑠3 } → 𝑠1 . 4.5 Multi-SuperHyperGraph A Multi-Superhypergraph is a loopless 𝑛-SuperHyperGraph allowing parallel superedges, modeling multisetstyle higher-order connections among repeated or weighted supervertex groups [5]. A Multi-SuperHyperGraph is an extension of both MultiGraphs [330, 331] and MultiHyperGraphs [332, 333]. Also, related concepts such as Fuzzy MultiGraphs [331, 334], Directed Multigraphs [19, 335–338], Soft multigraphs [339, 340], and Neutrosophic MultiGraphs [341, 342] are known. Definition 4.5.1 (Undirected multigraph). [330, 331] Let 𝑉 be a nonempty set of vertices. Write [𝑉] 2 := {𝑢, 𝑣} ⊆ 𝑉 | 𝑢 ≠ 𝑣 , [𝑉] ≤2 := [𝑉] 2 ∪ {𝑣} | 𝑣 ∈ 𝑉 . An (undirected) multigraph is a triple 𝐺 = (𝑉, 𝐸, 𝜕), where 𝐸 is a finite set of edges and 𝜕 : 𝐸 −→ [𝑉] ≤2 is the endpoint map. For 𝑒 ∈ 𝐸, the set 𝜕 (𝑒) is the (unordered) set of endpoints of 𝑒. • 𝑒 is a loop if |𝜕 (𝑒)| = 1. • Distinct edges 𝑒 1 ≠ 𝑒 2 are parallel if 𝜕 (𝑒 1 ) = 𝜕 (𝑒 2 ). • For 𝐹 ∈ [𝑉] ≤2 , the multiplicity of 𝐹 is 𝑚 𝐺 (𝐹) := { 𝑒 ∈ 𝐸 | 𝜕 (𝑒) = 𝐹 } . Equivalently, a multigraph is specified by a function 𝜇𝐺 : [𝑉] ≤2 → N with finite support, where 𝜇𝐺 (𝐹) = 𝑚 𝐺 (𝐹). Definition 4.5.2 (Loopless multigraph). A multigraph 𝐺 = (𝑉, 𝐸, 𝜕) is loopless if |𝜕 (𝑒)| = 2 for every 𝑒 ∈ 𝐸 (equivalently, 𝜇𝐺 ({𝑣}) = 0 for all 𝑣 ∈ 𝑉). 64

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Definition 4.5.3 (Multihypergraph). [332, 333] Let 𝑉 be a nonempty set. Put
P∗ (𝑉) := P (𝑉) \ {∅}.
A multihypergraph is a triple
𝐻 = (𝑉, 𝐸, 𝜕),
where 𝐸 is a finite set of hyperedges and
𝜕 : 𝐸 −→ P∗ (𝑉)
is the boundary map. For 𝑒 ∈ 𝐸, the set 𝜕 (𝑒) is the vertex-set incident with 𝑒.
• 𝑒 is a loop hyperedge if |𝜕 (𝑒)| = 1.
• Distinct hyperedges 𝑒 1 ≠ 𝑒 2 are parallel if 𝜕 (𝑒 1 ) = 𝜕 (𝑒 2 ).
• For 𝐹 ∈ P∗ (𝑉), the multiplicity of 𝐹 is
𝑚 𝐻 (𝐹) := { 𝑒 ∈ 𝐸 | 𝜕 (𝑒) = 𝐹 } .
Equivalently, a multihypergraph is specified by a function 𝜇 𝐻 : P∗ (𝑉) → N with finite support, where
𝜇 𝐻 (𝐹) = 𝑚 𝐻 (𝐹).
Definition 4.5.4 (Loopless multihypergraph). A multihypergraph 𝐻 = (𝑉, 𝐸, 𝜕) is loopless if |𝜕 (𝑒)| ≥ 2 for
every 𝑒 ∈ 𝐸 (equivalently, 𝜇 𝐻 ({𝑣}) = 0 for all 𝑣 ∈ 𝑉).
Definition 4.5.5 (Loops, parallel superedges, and multiplicity). Let SHG (𝑛) = (𝑉, 𝐸, 𝜕) be an 𝑛-SuperHyperGraph.
• A superedge 𝑒 ∈ 𝐸 is called a loop superedge if 𝜕 (𝑒) = 1.
• Two distinct superedges 𝑒 1 , 𝑒 2 ∈ 𝐸 are called parallel if
𝜕 (𝑒 1 ) = 𝜕 (𝑒 2 ).
• For 𝐹 ∈ P∗ (𝑉), the multiplicity of the incidence pattern 𝐹 is
𝑚(𝐹) := { 𝑒 ∈ 𝐸 | 𝜕 (𝑒) = 𝐹 } .
Thus the family of superedges can be viewed as a finite multiset {𝜕 (𝑒) | 𝑒 ∈ 𝐸 } of nonempty subsets of 𝑉
together with the multiplicity function 𝑚.
Definition 4.5.6 (Multi 𝑛-SuperHyperGraph). [5] An 𝑛-SuperHyperGraph SHG (𝑛) = (𝑉, 𝐸, 𝜕) is called a
Multi 𝑛-SuperHyperGraph if
• it is loopless, i.e. 𝜕 (𝑒) ≥ 2 for every 𝑒 ∈ 𝐸;
• parallel superedges are allowed, i.e. the incidence map 𝜕 is not required to be injective, so some 𝐹 ∈ P∗ (𝑉)
may satisfy 𝑚(𝐹) ≥ 2.
Equivalently, a Multi 𝑛-SuperHyperGraph is an 𝑛-SuperHyperGraph whose edge family is an arbitrary finite
multiset of nonempty subsets of 𝑉 of size at least 2. For 𝑛 = 0 this reduces to the usual notion of a loopless
multihypergraph.
Example 4.5.7 (A simple Multi 1-SuperHyperGraph with parallel superedges). We construct a loopless
1-SuperHyperGraph with parallel superedges, modeling repeated collaborations between the same employee–
team pair.
Step 1: Vertex tiers. Let the base (tier 0) vertex set be
𝑉0 := {𝑝, 𝑞},
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where 𝑝 and 𝑞 represent two employees.
Define a tier 1 vertex
𝑇 := {𝑝, 𝑞},
representing a team that consists of both employees 𝑝 and 𝑞. Set
𝑉1 := {𝑇 }.
The total vertex set of the 1-SuperHyperGraph is
𝑉 := 𝑉0 ∪ 𝑉1 = {𝑝, 𝑞, 𝑇 }.

Step 2: Superedges and boundary map. We introduce three superedges
𝐸 := {𝑒 1 , 𝑒 2 , 𝑒 3 }
and define the boundary map 𝜕 : 𝐸 → P ∗ (𝑉) by
𝜕 (𝑒 1 ) := {𝑝, 𝑇 },

𝜕 (𝑒 2 ) := {𝑝, 𝑇 },

𝜕 (𝑒 3 ) := {𝑞, 𝑇 }.

Intuitively:
• 𝑒 1 and 𝑒 2 encode two different projects where employee 𝑝 works with team 𝑇;
• 𝑒 3 encodes a project where employee 𝑞 works with the same team 𝑇.
Thus
SHG (1) := (𝑉, 𝐸, 𝜕)
is a level-1 SuperHyperGraph whose vertices come from two tiers (𝑝, 𝑞 at tier 0 and 𝑇 at tier 1), and whose
superedges connect these across tiers.
Step 3: Loopless property. A loop superedge is defined by the condition 𝜕 (𝑒) = 1. Here we have
𝜕 (𝑒 1 ) = {𝑝, 𝑇 },

𝜕 (𝑒 2 ) = {𝑝, 𝑇 },

𝜕 (𝑒 3 ) = {𝑞, 𝑇 },

so
|𝜕 (𝑒 1 )| = |𝜕 (𝑒 2 )| = |𝜕 (𝑒 3 )| = 2 ≥ 2.
Hence there are no loop superedges, and SHG (1) is loopless.
Step 4: Parallel superedges and multiplicity. By definition, two distinct superedges 𝑒 1 , 𝑒 2 ∈ 𝐸 are parallel
if 𝜕 (𝑒 1 ) = 𝜕 (𝑒 2 ).
In this example,
𝜕 (𝑒 1 ) = {𝑝, 𝑇 }

and

𝜕 (𝑒 2 ) = {𝑝, 𝑇 },

so 𝑒 1 and 𝑒 2 are parallel superedges.
For the incidence pattern
𝐹 := {𝑝, 𝑇 } ∈ P ∗ (𝑉),
its multiplicity is
𝑚(𝐹) := { 𝑒 ∈ 𝐸 | 𝜕 (𝑒) = 𝐹 } = {𝑒 1 , 𝑒 2 } = 2.
For the other incidence pattern {𝑞, 𝑇 }, we have
𝑚({𝑞, 𝑇 }) = 1,
66

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Chapter 4. Some Particular SuperHyperGraphs corresponding to the single superedge 𝑒 3 . Therefore, the edge family of SHG (1) can be viewed as the finite multiset {𝜕 (𝑒) | 𝑒 ∈ 𝐸 } = {𝑝, 𝑇 }, {𝑝, 𝑇 }, {𝑞, 𝑇 } , with multiplicities 𝑚({𝑝, 𝑇 }) = 2 and 𝑚({𝑞, 𝑇 }) = 1. Conclusion. The structure SHG (1) = (𝑉, 𝐸, 𝜕) is loopless (every superedge is incident with at least two vertices) and has parallel superedges (𝑒 1 and 𝑒 2 share the same incidence pattern). Hence it is a Multi 1-SuperHyperGraph in the sense of the definition: its superedge family is an arbitrary finite multiset of nonempty subsets of 𝑉 of size at least 2. 4.6 Semi-SuperHyperGraph Semigraphs generalize graphs by using ordered vertex tuples as edges, permitting varying edge sizes and controlled pairwise intersections among them [42, 343, 344]. Semihypergraphs extend semigraph tuples to hyperedges, using ordered vertex sequences of arbitrary length, with restricted intersections and reversal equivalence criteria [43,345]. A Semi-Superhypergraph is an n-SuperHyperGraph without parallel superedges, permitting loops, thus representing unique incidence patterns with possible self-connected supervertices [5]. Definition 4.6.1 (SemiGraph (Semigraph)). [42, 343, 344] Let 𝑉 be a nonempty set, and let 𝐸 be a set of ordered tuples of distinct vertices from 𝑉, each of length at least 2. A semigraph is a pair 𝐺 = (𝑉, 𝐸) satisfying: (1) Intersection condition: any two edges in 𝐸 have at most one vertex in common. (2) Reversal equivalence: for edges 𝐸 1 = (𝑢 1 , . . . , 𝑢 𝑚 ) and 𝐸 2 = (𝑣 1 , . . . , 𝑣 𝑛 ), we consider 𝐸 1 = 𝐸 2 iff 𝑚 = 𝑛 and either 𝑢 𝑖 = 𝑣 𝑖 for all 𝑖, or 𝑢 𝑖 = 𝑣 𝑛−𝑖+1 for all 𝑖. Definition 4.6.2 (SemiHyperGraph (Semihypergraph)). [43] A semihypergraph is a pair 𝐻𝑠 = (𝑉, 𝐸 ℎ ) where 𝑉 is a finite nonempty set of vertices and 𝐸 ℎ is a set of ordered tuples of distinct vertices from 𝑉, each of length at least 2, such that: (1) Intersection condition: any two hyperedges in 𝐸 ℎ have at most one vertex in common. ℎ = (𝑢 , . . . , 𝑢 ) and 𝐸 ℎ = (𝑣 , . . . , 𝑣 ), we consider 𝐸 ℎ = 𝐸 ℎ (2) Reversal equivalence: for hyperedges 𝐸 𝑚 1 𝑚 1 𝑛 𝑛 𝑚 𝑛 iff 𝑚 = 𝑛 and either 𝑢 𝑖 = 𝑣 𝑖 for all 𝑖, or 𝑢 𝑖 = 𝑣 𝑛−𝑖+1 for all 𝑖. Example 4.6.3 (A simple SemiHyperGraph (Semihypergraph)). Let 𝑉 := {1, 2, 3, 4, 5, 6}. Define a family of ordered hyperedges (tuples of distinct vertices, each of length ≥ 2) by 𝐸 ℎ := 𝑒 1 := (1, 2, 3), 𝑒 2 := (3, 4), 𝑒 3 := (5, 6) . Then 𝐻𝑠 = (𝑉, 𝐸 ℎ ) is a semihypergraph: (1) Intersection condition. We have 𝑒 1 ∩ 𝑒 2 = {3}, 𝑒 1 ∩ 𝑒 3 = ∅, 𝑒 2 ∩ 𝑒 3 = ∅, so any two hyperedges share at most one vertex. (2) Reversal equivalence. For instance, the tuple (1, 2, 3) represents the same hyperedge as its reversal (3, 2, 1), while it is different from (1, 3, 2) because that is neither identical to (1, 2, 3) nor its reversal. 67

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Thus 𝐻𝑠 = (𝑉, 𝐸 ℎ ) is a concrete example of a SemiHyperGraph.
Definition 4.6.4 (Semi 𝑛-SuperHyperGraph). [5] An 𝑛-SuperHyperGraph SHG (𝑛) = (𝑉, 𝐸, 𝜕) is called a
Semi 𝑛-SuperHyperGraph if

• parallel superedges are forbidden, i.e. 𝜕 is injective:
𝜕 (𝑒 1 ) = 𝜕 (𝑒 2 ) =⇒ 𝑒 1 = 𝑒 2

for all 𝑒 1 , 𝑒 2 ∈ 𝐸;

• loop superedges are allowed, i.e. we permit superedges 𝑒 ∈ 𝐸 with 𝜕 (𝑒) = 1.

Thus a Semi 𝑛-SuperHyperGraph is an 𝑛-SuperHyperGraph with no parallel superedges but with possible
loops. For 𝑛 = 0 this is the natural analogue of a loop-allowing simple hypergraph (no parallel hyperedges).
Example 4.6.5 (A simple Semi 1-SuperHyperGraph). Let the base set of elements be
𝑆 := {𝑎, 𝑏, 𝑐}.
Then
P 0 (𝑆) = 𝑆,

P 1 (𝑆) = P (𝑆).

Define two 1-supervertices
𝐴 := {𝑎, 𝑏},

𝐵 := {𝑏, 𝑐},

and set
𝑉 := {𝐴, 𝐵} ⊆ P 1 (𝑆).

Next, take a set of superedges
𝐸 := {𝑒 1 , 𝑒 2 },
and define the incidence map
𝜕 : 𝐸 −→ P∗ (𝑉)
by
𝜕 (𝑒 1 ) := {𝐴, 𝐵},

𝜕 (𝑒 2 ) := {𝐴}.

Then
SHG (1) := (𝑉, 𝐸, 𝜕)
is a 1-SuperHyperGraph. We now check the Semi 1-SuperHyperGraph conditions:

• There are no parallel superedges, because 𝜕 (𝑒 1 ) = {𝐴, 𝐵} ≠ {𝐴} = 𝜕 (𝑒 2 ), so 𝜕 is injective on 𝐸.
• A loop superedge is present: 𝑒 2 satisfies 𝜕 (𝑒 2 ) = |{𝐴}| = 1, so 𝑒 2 is a loop at the supervertex 𝐴.

Therefore, SHG (1) is a Semi 1-SuperHyperGraph: it has no parallel superedges, but it does allow a loop on the
supervertex 𝐴.

Table 4.5 presents an overview of SemiGraphs, SemiHyperGraphs, and Semi n-SuperHyperGraphs.
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Model

Carrier objects

SemiGraph

Vertices 𝑉

SemiHyperGraph

Vertices 𝑉

Semi
𝑛- 𝑛-supervertices
SuperHyperGraph
P𝑛 (𝑉0 )

𝑉 (𝑛)

Edge / hyperedge / superedge rule
(informal)
Edges are ordered tuples
(𝑢 1 , . . . , 𝑢 𝑚 ) of distinct vertices
(𝑚 ≥ 2); any two edges intersect
in at most one vertex; tuple
reversal is identified.
Hyperedges are ordered tuples
(𝑢 1 , . . . , 𝑢 𝑚 ) of distinct vertices
(𝑚 ≥ 2); any two hyperedges intersect in at most one vertex; tuple reversal is identified.
⊆ Superedges are subsets of 𝑉 (𝑛)
(incidence patterns); no parallel
superedges (incidence map injective); loop superedges 𝜕 (𝑒) = 1
are allowed.

Table 4.5: Overview of SemiGraphs, SemiHyperGraphs, and Semi 𝑛-SuperHyperGraphs

4.7

Pseudo-SuperHyperGraph

A pseudograph is a graph allowing loops and parallel edges, modeling repeated connections and self-interactions
between vertices simultaneously, explicitly, often [346, 347]. Related concepts such as fuzzy pseudographs
are also known [348–350]. A pseudo-hypergraph permits repeated hyperedges and loops, allowing identical
vertex-subsets as distinct hyperedges for multiplicity in models of complex systems [351, 352]. A PseudoSuperhypergraph is the most general n-SuperHyperGraph, allowing both loops and parallel superedges, capturing arbitrary nonempty incidence configurations [5].
Definition 4.7.1 (Pseudo 𝑛-SuperHyperGraph). [5] An 𝑛-SuperHyperGraph SHG (𝑛) = (𝑉, 𝐸, 𝜕) is called a
Pseudo 𝑛-SuperHyperGraph if both loop superedges and parallel superedges are allowed. Equivalently, we
impose only the basic conditions
∅ ≠ 𝜕 (𝑒) ⊆ 𝑉 for all 𝑒 ∈ 𝐸,
and place no restrictions on the cardinalities 𝜕 (𝑒) or on the injectivity of 𝜕. Hence a Pseudo 𝑛-SuperHyperGraph
is the most general (nonempty-incidence) form of 𝑛-SuperHyperGraph; Multi and Semi 𝑛-SuperHyperGraphs
appear as special cases obtained by forbidding loops or parallel superedges, respectively. For 𝑛 = 0 this
coincides with the usual notion of a pseudohypergraph (loops and multiple hyperedges allowed).
Example 4.7.2 (A simple Pseudo 1-SuperHyperGraph). Let the base set be
𝑆 := {𝑥, 𝑦}.
Then
P 0 (𝑆) = 𝑆,

P 1 (𝑆) = P (𝑆).

Define two 1-supervertices
𝐴 := {𝑥},

𝐵 := {𝑥, 𝑦},

and set
𝑉 := {𝐴, 𝐵} ⊆ P 1 (𝑆).
Next, take a set of superedges
𝐸 := {𝑒 1 , 𝑒 2 , 𝑒 3 },
and define the incidence map
𝜕 : 𝐸 −→ P∗ (𝑉)
by
𝜕 (𝑒 1 ) := {𝐴, 𝐵},

𝜕 (𝑒 2 ) := {𝐴, 𝐵},
69

𝜕 (𝑒 3 ) := {𝐵}.

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Chapter 4. Some Particular SuperHyperGraphs
Then
SHG (1) := (𝑉, 𝐸, 𝜕)
is a 1-SuperHyperGraph. It is a Pseudo 1-SuperHyperGraph because:
• 𝑒 1 and 𝑒 2 are parallel superedges, since 𝜕 (𝑒 1 ) = 𝜕 (𝑒 2 ) = {𝐴, 𝐵}.
• 𝑒 3 is a loop superedge at the supervertex 𝐵, since 𝜕 (𝑒 3 ) = |{𝐵}| = 1.
• No further restrictions are imposed on 𝜕, apart from ∅ ≠ 𝜕 (𝑒) ⊆ 𝑉 for all 𝑒 ∈ 𝐸.
Thus (𝑉, 𝐸, 𝜕) provides a concrete example of a Pseudo 1-SuperHyperGraph.

4.8

Directed Multi-SuperHyperGraph

A directed multigraph is a directed graph that permits parallel directed edges between the same ordered pair of
vertices, thereby recording multiplicities of repeated interactions [353–355]. A directed multihypergraph is a
directed hypergraph that permits parallel directed hyperedges (hyperarcs) from a tail set of vertices to a head set
of vertices, so that one can model repeated higher-order directed relations. A directed multi-superhypergraph is
a tiered directed multihypergraph whose vertex universe may include supervertices built via iterated powersets,
and it permits parallel directed superhyperedges from a nonempty tail supervertex-set to a nonempty head
supervertex-set.
Definition 4.8.1 (Directed multigraph). (cf. [353–355]) A directed multigraph is a tuple
𝐺 = (𝑉, 𝐴, 𝑠, 𝑡),
where 𝑉 ≠ ∅ is a set of vertices, 𝐴 is a (finite or infinite) set of arc identifiers, and 𝑠, 𝑡 : 𝐴 → 𝑉 are the source
and target maps. An element 𝑎 ∈ 𝐴 represents the directed arc 𝑠(𝑎) → 𝑡 (𝑎).
Two distinct arcs 𝑎 1 ≠ 𝑎 2 are parallel if (𝑠(𝑎 1 ), 𝑡 (𝑎 1 )) = (𝑠(𝑎 2 ), 𝑡 (𝑎 2 )). An arc 𝑎 is a loop if 𝑠(𝑎) = 𝑡 (𝑎).
If 𝐴 is finite, then 𝐺 is called a finite directed multigraph.
Remark 4.8.2 (Multiplicity-function presentation). Equivalently, a directed multigraph can be given by a
multiplicity function
𝜇 : 𝑉 ×𝑉 → N
(with N = {0, 1, 2, . .Í. }), where 𝜇(𝑢, 𝑣) is the number of parallel arcs from 𝑢 to 𝑣. This is equivalent to
(𝑉, 𝐴, 𝑠, 𝑡) whenever (𝑢,𝑣) ∈𝑉 ×𝑉 𝜇(𝑢, 𝑣) < ∞ (finite support).
Definition 4.8.3 (Directed multihypergraph). A directed multihypergraph is a directed hypergraph
𝐻 = (𝑉, 𝐸, 𝜕 − , 𝜕 + )
in which parallel hyperarcs are allowed, i.e. (𝜕 − , 𝜕 + ) is not required to be injective. Thus, distinct 𝑒 1 ≠ 𝑒 2
may satisfy


𝜕 − (𝑒 1 ), 𝜕 + (𝑒 1 ) = 𝜕 − (𝑒 2 ), 𝜕 + (𝑒 2 ) ,
and this equality encodes multiplicity.
A hyperarc 𝑒 is a loop-hyperarc if 𝜕 − (𝑒) = 𝜕 + (𝑒) (in particular, a vertex-loop occurs when 𝜕 − (𝑒) = 𝜕 + (𝑒) = {𝑣}
for some 𝑣 ∈ 𝑉).
If 𝐸 is finite, then 𝐻 is called a finite directed multihypergraph.
Remark 4.8.4 (Multiplicity-function presentation and reduction). Equivalently, a directed multihypergraph
can be represented by a multiplicity function
𝜇 : P ∗ (𝑉) × P ∗ (𝑉) → N,
where 𝜇(𝑇, 𝐻) counts how many directed hyperarcs have tail 𝑇 and head 𝐻, typically assuming finite support
for a finite structure.
A directed multigraph is recovered as the special case where every tail and head is a singleton:
𝜕 − (𝑒) = {𝑢}, 𝜕 + (𝑒) = {𝑣}

⇐⇒

𝑒 is an arc 𝑢 → 𝑣 (with possible multiplicity).
70

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Chapter 4. Some Particular SuperHyperGraphs
Definition 4.8.5 (𝑛-tier supervertex universe). Fix an integer 𝑛 ≥ 0 and a nonempty base set 𝑉0 . For each
𝑘 ∈ {1, . . . , 𝑛} choose a set
𝑉𝑘 ⊆ P 𝑘 (𝑉0 ),
whose elements are called level-𝑘 supervertices. Define the total (tiered) supervertex universe by
b(𝑛) :=
𝑉

𝑛
Ø

𝑉𝑘 .

𝑘=0

b(𝑛) =
Definition
4.8.6 (Directed Multi 𝑛-SuperHyperGraph). Fix 𝑛 ≥ 0 and a tiered supervertex universe 𝑉
Ð𝑛
𝑘=0 𝑉𝑘 as above. A directed multi 𝑛-superhypergraph is a tuple

𝑛
DMSHG (𝑛) := 𝑉0 , (𝑉𝑘 ) 𝑘=1
, 𝐸, 𝜕 − , 𝜕 + ,
where 𝐸 is a set of directed superedge identifiers and
b(𝑛)
𝜕 − , 𝜕 + : 𝐸 −→ P ∗ 𝑉



are the tail and head incidence maps. For each 𝑒 ∈ 𝐸, the ordered pair
𝑒 : 𝜕 − (𝑒) −→ 𝜕 + (𝑒)
is a directed superedge from the (nonempty) tail set to the (nonempty) head set.
Two distinct directed superedges 𝑒 1 ≠ 𝑒 2 are called parallel if
𝜕 − (𝑒 1 ) = 𝜕 − (𝑒 2 )

and

𝜕 + (𝑒 1 ) = 𝜕 + (𝑒 2 ).

Definition 4.8.7 (Multiplicity of a directed incidence pattern). Let DMSHG (𝑛) be a directed multi 𝑛-superhypergraph.
b(𝑛) ) × P ∗ (𝑉
b(𝑛) ) define its multiplicity by
For (𝑇, 𝐻) ∈ P ∗ (𝑉
𝑚(𝑇, 𝐻) := { 𝑒 ∈ 𝐸 | 𝜕 − (𝑒) = 𝑇, 𝜕 + (𝑒) = 𝐻 } .
Thus the directed superedge family may be viewed as a finite or infinite multiset of ordered pairs (𝑇, 𝐻) with
𝑇, 𝐻 ≠ ∅.
Remark 4.8.8 (Loop edges and the loopless variant). A directed superedge 𝑒 may satisfy 𝜕 − (𝑒) = 𝜕 + (𝑒); this
is a (set-)loop. If one wishes to forbid such loops, one may additionally require 𝜕 − (𝑒) ≠ 𝜕 + (𝑒) for all 𝑒 ∈ 𝐸;
the present definition does not impose this.
Example 4.8.9 (A concrete directed multi 1-superhypergraph with parallel directed superedges). We model
a small workflow in which two analysts repeatedly submit reports to the same review committee, and the
committee forwards the approved material to an archive.
Step 1: Tiered supervertex universe. Let the base (tier 0) vertex set be
𝑉0 := {𝑎, 𝑏, 𝑐},
where 𝑎, 𝑏 are two analysts and 𝑐 is an archivist.
Define tier 1 supervertices (subsets of 𝑉0 ):
𝑅 := {𝑎, 𝑏},

𝐶 := {𝑎, 𝑏, 𝑐}.

Set
𝑉1 := {𝑅, 𝐶} ⊆ P (𝑉0 ),

b(1) := 𝑉0 ∪ 𝑉1 = {𝑎, 𝑏, 𝑐, 𝑅, 𝐶}.
𝑉

Step 2: Directed superedge identifiers. Let
𝐸 := {𝑒 1 , 𝑒 2 , 𝑒 3 }.
71

73.

Chapter 4. Some Particular SuperHyperGraphs Intuitively, 𝑒 1 and 𝑒 2 represent two distinct submissions of the same type (hence parallel), while 𝑒 3 represents forwarding to the archive. Step 3: Tail/head incidence maps. Define b(1) 𝜕 − , 𝜕+ : 𝐸 → P∗ 𝑉 by 𝜕 − (𝑒 1 ) = {𝑎, 𝑅}, 𝜕 + (𝑒 1 ) = {𝐶}, 𝜕 − (𝑒 2 ) = {𝑎, 𝑅}, 𝜕 + (𝑒 2 ) = {𝐶}, 𝜕 − (𝑒 3 ) = {𝐶}, 𝜕 + (𝑒 3 ) = {𝑐}. Hence each 𝑒 ∈ 𝐸 is a directed superedge 𝑒 : 𝜕 − (𝑒) −→ 𝜕 + (𝑒), with nonempty tail and head sets. Step 4: Parallelism and multiplicities. Since 𝜕 − (𝑒 1 ) = 𝜕 − (𝑒 2 ) = {𝑎, 𝑅} and 𝜕 + (𝑒 1 ) = 𝜕 + (𝑒 2 ) = {𝐶}, the directed superedges 𝑒 1 and 𝑒 2 are parallel. Let (𝑇, 𝐻) := {𝑎, 𝑅}, {𝐶} . Then the multiplicity of this directed incidence pattern is 𝑚(𝑇, 𝐻) = { 𝑒 ∈ 𝐸 | 𝜕 − (𝑒) = {𝑎, 𝑅}, 𝜕 + (𝑒) = {𝐶} } = {𝑒 1 , 𝑒 2 } = 2. Also, for (𝑇 ′ , 𝐻 ′ ) := {𝐶}, {𝑐} , we have 𝑚(𝑇 ′ , 𝐻 ′ ) = 1. Conclusion. The structure DMSHG (1) := 𝑉0 , (𝑉1 ), 𝐸, 𝜕 − , 𝜕 + is a directed multi 1-superhypergraph. It is genuinely “multi” because the same directed incidence pattern {𝑎, 𝑅} → {𝐶} occurs with multiplicity 2 (via 𝑒 1 and 𝑒 2 ), and it is “superhyper” because it uses tier-1 supervertices 𝑅, 𝐶 ∈ P (𝑉0 ). Theorem 4.8.10 (Directed multihypergraphs are exactly the 𝑛 = 0 case). Let 𝑛 = 0 and let 𝑉0 be a nonempty set. Then a directed multi 0-superhypergraph DMSHG (0) = 𝑉0 , 𝐸, 𝜕 − , 𝜕 + is precisely a directed multihypergraph on 𝑉0 in the standard sense: 𝜕 − , 𝜕 + : 𝐸 → P ∗ (𝑉0 ). Conversely, every directed multihypergraph 𝐻 = (𝑉, 𝐸, 𝜕 − , 𝜕 + ) is canonically a directed multi 0-superhypergraph b(0) = 𝑉0 . by taking 𝑉0 := 𝑉 and 𝑉 b(0) = 𝑉0 and there are no higher tiers. By Definition, a directed multi 0Proof. When 𝑛 = 0 we have 𝑉 superhypergraph consists of a vertex set 𝑉0 , a set 𝐸 of hyperarc identifiers, and maps 𝜕 − , 𝜕 + : 𝐸 → P ∗ (𝑉0 ). This is exactly the usual definition of a directed multihypergraph: each 𝑒 ∈ 𝐸 is a directed hyperarc from tail set 𝜕 − (𝑒) to head set 𝜕 + (𝑒), and multiplicity is encoded by allowing distinct identifiers 𝑒 1 ≠ 𝑒 2 with the same ordered pair (𝜕 − (𝑒), 𝜕 + (𝑒)). b(0) = 𝑉0 . Conversely, given a directed multihypergraph 𝐻 = (𝑉, 𝐸, 𝜕 − , 𝜕 + ), set 𝑉0 := 𝑉 and observe that 𝑉 Then 𝐻 matches the data of a directed multi 0-superhypergraph without any modification. □ 72

74.

Chapter 4. Some Particular SuperHyperGraphs Theorem 4.8.11 (Directed superhypergraphs are obtained by forbidding parallel edges). Let DMSHG (𝑛) = 𝑛 − + 𝑉0 , (𝑉𝑘 ) 𝑘=1 , 𝐸, 𝜕 , 𝜕 be a directed multi 𝑛-superhypergraph. Assume that the pair map b(𝑛) ) × P ∗ (𝑉 b(𝑛) ), (𝜕 − , 𝜕 + ) : 𝐸 −→ P ∗ (𝑉 𝑒 ↦−→ 𝜕 − (𝑒), 𝜕 + (𝑒) , is injective (equivalently, there are no parallel directed superedges). Define b(𝑛) ) × P ∗ (𝑉 b(𝑛) ). E := 𝜕 − (𝑒), 𝜕 + (𝑒) | 𝑒 ∈ 𝐸 ⊆ P ∗ (𝑉 Then 𝑛 DSHG (𝑛) := 𝑉0 , (𝑉𝑘 ) 𝑘=1 , E, 𝜋 − , 𝜋 + is a directed 𝑛-superhypergraph, and DMSHG (𝑛) and DSHG (𝑛) carry the same directed incidence information (each 𝑒 ∈ 𝐸 corresponds to exactly one element of E). b(𝑛) , so E ⊆ P ∗ (𝑉 b(𝑛) ) × P ∗ (𝑉 b(𝑛) ). Proof. By construction, E is a set of ordered pairs of nonempty subsets of 𝑉 (𝑛) Hence DSHG satisfies Definition of a directed 𝑛-superhypergraph. Injectivity of (𝜕 − , 𝜕 + ) implies that the assignment Φ : 𝐸 −→ E, Φ(𝑒) := 𝜕 − (𝑒), 𝜕 + (𝑒) , is a bijection onto its image E. Moreover, for every 𝑒 ∈ 𝐸 we have 𝜋 − Φ(𝑒) = 𝜋 − 𝜕 − (𝑒), 𝜕 + (𝑒) = 𝜕 − (𝑒), 𝜋 + Φ(𝑒) = 𝜕 + (𝑒). Thus the directed incidence of 𝑒 in DMSHG (𝑛) is exactly the directed incidence of Φ(𝑒) in DSHG (𝑛) . Therefore, forbidding parallel edges (injectivity) converts the multiset-of-edges presentation into a set-of-patterns presentation, i.e. a directed superhypergraph. □ 4.9 Signed SuperHyperGraph A Signed SuperHyperGraph assigns positive or negative incidence signs to multi-level superedges connecting nested supervertices, thereby extending the structural ideas of classical signed hypergraphs [356]. The concept of a Signed SuperHyperGraph applies and generalizes the principles of both Signed Graphs [357–359] and Signed HyperGraphs [360,361]. In addition, related concepts such as signed fuzzy graphs [362–365], weighted signed graphs [366, 367], and signed neutrosophic graphs [368, 369] are also well known. Definition 4.9.1 (Signed HyperGraph). [360, 361] Let 𝐻 = (𝑉, 𝐸) be a finite hypergraph, where 𝑉 is a nonempty set of vertices and 𝐸 ⊆ P (𝑉) \ {∅} is a finite family of nonempty hyperedges. A signed hypergraph on 𝐻 is a triple 𝐻 ± = (𝑉, 𝐸, 𝜑), where 𝜑 : 𝑉 × 𝐸 → {−1, 0, +1} is called the incidence sign function and satisfies   +1,     𝜑(𝑣, 𝑒) = −1,     0,  if 𝑣 ∈ 𝑒 and the incidence of 𝑣 in 𝑒 is declared positive, if 𝑣 ∈ 𝑒 and the incidence of 𝑣 in 𝑒 is declared negative, if 𝑣 ∉ 𝑒. For a vertex–hyperedge pair (𝑣, 𝑒), we say that the incidence is positive if 𝜑(𝑣, 𝑒) = +1 and negative if 𝜑(𝑣, 𝑒) = −1. The underlying hypergraph of 𝐻 ± is the pair (𝑉, 𝐸). When every hyperedge 𝑒 ∈ 𝐸 has cardinality 2, this notion reduces to the usual concept of a signed graph. 73

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Chapter 4. Some Particular SuperHyperGraphs
Example 4.9.2 (A simple signed hypergraph). Let the vertex set and hyperedge family be
𝑉 := {𝑎, 𝑏, 𝑐},

𝐸 := {𝑒 1 , 𝑒 2 },

𝑒 1 := {𝑎, 𝑏},

𝑒 2 := {𝑏, 𝑐}.

with hyperedges
Define the incidence sign function 𝜑 : 𝑉 × 𝐸 → {−1, 0, +1} by


+1,




𝜑(𝑣, 𝑒) = −1,



 0,


if (𝑣, 𝑒) ∈ {(𝑎, 𝑒 1 ), (𝑏, 𝑒 2 )},
if (𝑣, 𝑒) ∈ {(𝑏, 𝑒 1 ), (𝑐, 𝑒 2 )},
otherwise.

Equivalently, the values of 𝜑 on incidences with 𝑣 ∈ 𝑒 are
𝜑(𝑎, 𝑒 1 ) = +1,

𝜑(𝑏, 𝑒 1 ) = −1,

𝜑(𝑏, 𝑒 2 ) = +1,

𝜑(𝑐, 𝑒 2 ) = −1,

and 𝜑(𝑣, 𝑒) = 0 whenever 𝑣 ∉ 𝑒. Then 𝐻 ± = (𝑉, 𝐸, 𝜑) is a signed hypergraph: each hyperedge connects its
incident vertices with specified positive or negative incidences.
Definition 4.9.3 (Signed 𝑛-SuperHyperGraph). [356] Let 𝑉0 be a finite base set, and for each integer 𝑘 ≥ 0
define the iterated powersets

P0 (𝑉0 ) := 𝑉0 ,
P 𝑘+1 (𝑉0 ) := P P 𝑘 (𝑉0 ) ,
where P(𝑋) denotes the usual powerset of a set 𝑋. Fix 𝑛 ∈ N0 .
A signed 𝑛-SuperHyperGraph is a triple
SWSuHyG(𝑛) = (𝑉, 𝐸, 𝜑),
where
• 𝑉 ⊆ P𝑛 (𝑉0 ) is a finite set of 𝑛-supervertices;
• 𝐸 ⊆ P𝑛+1 (𝑉0 ) is a finite family of 𝑛-superedges, and each 𝑒 ∈ 𝐸 is a nonempty subset of 𝑉 (so
𝐸 ⊆ P (𝑉) \ {∅} and, in particular, 𝐸 ⊆ P𝑛+1 (𝑉0 ));
• 𝜑 : 𝑉 × 𝐸 → {−1, 0, +1} is the incidence sign function, defined by


+1,




𝜑(𝑣, 𝑒) = −1,



 0,


if 𝑣 ∈ 𝑒 and the incidence of 𝑣 in 𝑒 is positive,
if 𝑣 ∈ 𝑒 and the incidence of 𝑣 in 𝑒 is negative,
if 𝑣 ∉ 𝑒.

We call an incidence (𝑣, 𝑒) positive if 𝜑(𝑣, 𝑒) = +1 and negative if 𝜑(𝑣, 𝑒) = −1.
When 𝑛 = 1, interpreting the elements of 𝑉 as vertices and the elements of 𝐸 as hyperedges recovers a signed
hypergraph in the above sense; if in addition every superedge 𝑒 ∈ 𝐸 has exactly two supervertices, we obtain a
signed graph.
Example 4.9.4 (A simple signed 1-SuperHyperGraph). Let the finite base set be
𝑉0 := {1, 2}.
Then
P0 (𝑉0 ) = 𝑉0 ,

P1 (𝑉0 ) = P(𝑉0 ) = {∅, {1}, {2}, {1, 2}},

and

P2 (𝑉0 ) = P P1 (𝑉0 ) .
Choose the set of 1-supervertices


𝑉 := 𝑤 1 , 𝑤 2 := {1}, {1, 2} ⊆ P1 (𝑉0 ),
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Chapter 4. Some Particular SuperHyperGraphs and define a single 1-superedge 𝑒 := {𝑤 1 , 𝑤 2 }, 𝐸 := {𝑒}. Since 𝑒 is a nonempty subset of 𝑉 and 𝑉 ⊆ P1 (𝑉0 ), we have 𝑒 ∈ P (𝑉) \ {∅} and also 𝑒 ∈ P2 (𝑉0 ), so the pair (𝑉, 𝐸) fits the structure of a 1-SuperHyperGraph. Define the incidence sign function 𝜑 : 𝑉 × 𝐸 → {−1, 0, +1} by   +1,     𝜑(𝑣, 𝑒) = −1,     0,  if 𝑣 = 𝑤 1 , if 𝑣 = 𝑤 2 , if 𝑣 ∉ 𝑒. Thus 𝑤 1 is positively incident with 𝑒, 𝑤 2 is negatively incident with 𝑒, and there are no other incidences. The triple SWSuHyG(1) := (𝑉, 𝐸, 𝜑) is a signed 1-SuperHyperGraph in the sense of the definition: 𝑉 is a finite subset of P1 (𝑉0 ), 𝐸 is a finite family of 1-superedges (each a nonempty subset of 𝑉 and hence an element of P2 (𝑉0 )), and 𝜑 assigns ±1 or 0 to each vertex–superedge pair according to membership. For reference, Table 4.6 provides an overview of the comparison between signed graphs, signed hypergraphs, and signed 𝑛-SuperHyperGraphs. Table 4.6: Comparison of signed graphs, signed hypergraphs, and signed 𝑛-SuperHyperGraphs Framework Underlying structure Incidence / sign assignment Signed graph Simple graph 𝐺 = (𝑉, 𝐸) with edges 𝑢𝑣 ∈ 𝐸 between vertex pairs. Signed hypergraph Hypergraph 𝐻 = (𝑉, 𝐸) with hyperedges 𝑒 ∈ 𝐸 ⊆ P∗ (𝑉). Edge-sign function 𝜎 : 𝐸 → {−1, +1}, or equivalently signs on incidences (𝑣, 𝑢𝑣) indicating positive or negative edges. Incidence sign function 𝜑 : 𝑉 × 𝐸 → {−1, 0, +1}, with 𝜑(𝑣, 𝑒) = 0 if 𝑣 ∉ 𝑒 and ±1 marking positive/negative incidences. Incidence sign function 𝜑 : 𝑉 × 𝐸 → {−1, 0, +1} on supervertex–superedge pairs, encoding positive/negative multi-level incidences across nested structures. Signed SuperHyperGraph 4.10 𝑛- 𝑛-SuperHyperGraph (𝑉, 𝐸) with 𝑉 ⊆ P𝑛 (𝑉0 ) and 𝐸 ⊆ P∗ (𝑉) of 𝑛superedges. Weighted SuperHyperGraph A weighted graph assigns numerical weights to edges or vertices, representing costs, capacities, distances, or strengths for optimization and analysis [370, 371]. Related notions are also known, such as HyperWeighted Graphs [372], Weighted Directed Graphs [325, 373, 374], Weighted Neutrosophic Graphs [375, 376], and Weighted Fuzzy Graphs [377–379]. A weighted hypergraph is a hypergraph whose vertices or hyperedges carry real-valued weights modeling capacities, costs, or strengths in applications [380–382]. A weighted SuperHypergraph is an n-level SuperHyperGraph assigning numerical weights to supervertices or superedges, encoding hierarchical importance or reliability scores [356] Definition 4.10.1 (Weighted hypergraph). [380–382] Let 𝑉 be a nonempty finite set and let 𝐸 ⊆ P (𝑉) \ {∅} be a finite family of nonempty subsets of 𝑉. The pair 𝐻 := (𝑉, 𝐸) 75

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Chapter 4. Some Particular SuperHyperGraphs
is called a hypergraph, and the elements of 𝐸 are its hyperedges.
A weighted hypergraph is a triple
W-HG := (𝑉, 𝐸, 𝑤),
where 𝐻 = (𝑉, 𝐸) is a hypergraph and
𝑤 : 𝐸 −→ R>0
is a weight function that assigns to each hyperedge 𝑒 ∈ 𝐸 a strictly positive real weight 𝑤(𝑒) (for example,
cost, capacity, strength of interaction, or frequency of co-occurrence). The underlying unweighted hypergraph
is recovered by forgetting the function 𝑤.
Example 4.10.2 (Weighted hypergraph: project collaboration intensity). Consider a small research lab with
four researchers
𝑉 := {𝑟 1 , 𝑟 2 , 𝑟 3 , 𝑟 4 }.
We model collaborative projects as hyperedges on 𝑉:

𝐸 := 𝑒 1 , 𝑒 2 , 𝑒 3 , 𝑒 1 := {𝑟 1 , 𝑟 2 }, 𝑒 2 := {𝑟 2 , 𝑟 3 , 𝑟 4 }, 𝑒 3 := {𝑟 1 , 𝑟 3 }.
Then
𝐻 := (𝑉, 𝐸)
is a hypergraph in the sense of the above definition.
Suppose that each hyperedge 𝑒 ∈ 𝐸 represents a multi-person project, and we assign a positive weight 𝑤(𝑒)
equal to the number of joint publications produced by the researchers in that project:
𝑤 : 𝐸 → R>0 ,

𝑤(𝑒 1 ) := 3,

𝑤(𝑒 2 ) := 5,

𝑤(𝑒 3 ) := 1.

The triple
W-HG := (𝑉, 𝐸, 𝑤)
is then a weighted hypergraph. The hyperedge 𝑒 2 has the largest weight, indicating that the collaboration among
{𝑟 2 , 𝑟 3 , 𝑟 4 } is the most productive (in terms of joint publications), while 𝑒 3 is the weakest collaboration in this
lab.
Definition 4.10.3 (Weighted SuperHyperGraph of depth 𝑛). [356] Let 𝑉0 be a nonempty finite base set and
let 𝑛 ∈ N0 . Let
SHG (𝑛) := (𝑉, 𝐸)
be an 𝑛-SuperHyperGraph on 𝑉0 , so that
𝑉 ⊆ P𝑛 (𝑉0 ),

𝐸 ⊆ P𝑛+1 (𝑉0 ).

A weighted SuperHyperGraph of depth 𝑛 on SHG (𝑛) is a triple
W-SHG (𝑛) := (𝑉, 𝐸, 𝑤),
where
𝑤 : 𝐸 −→ R>0
is a weight function that assigns to each 𝑛-superedge 𝑒 ∈ 𝐸 a strictly positive real weight 𝑤(𝑒). The value 𝑤(𝑒)
may encode, for example, the intensity, capacity, cost, reliability, or frequency of the higher–order, hierarchical
interaction represented by 𝑒.
In particular, when 𝑛 = 0 and 𝑉0 = 𝑉, the conditions
𝑉 ⊆ P0 (𝑉0 ) = 𝑉0 ,

𝐸 ⊆ P1 (𝑉0 ) = P (𝑉0 )

show that any weighted hypergraph (𝑉, 𝐸, 𝑤) can be regarded as a weighted SuperHyperGraph of depth 0.
Thus weighted SuperHyperGraphs strictly generalize weighted hypergraphs by allowing vertices and edges to
inhabit iterated powerset layers of arbitrary depth.
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Example 4.10.4 (Weighted SuperHyperGraph of depth 1: multi-team task forces). Let the finite base set of
employees be
𝑉0 := {𝑎, 𝑏, 𝑐, 𝑑}.
We work at depth 𝑛 = 1, so

P2 (𝑉0 ) = P P (𝑉0 ) .

P1 (𝑉0 ) = P (𝑉0 ),

Choose three teams (subsets of employees) and treat them as 1-supervertices:
𝑇1 := {𝑎, 𝑏},

𝑇2 := {𝑏, 𝑐},

𝑇3 := {𝑐, 𝑑},

and set
𝑉 := {𝑇1 , 𝑇2 , 𝑇3 } ⊆ P1 (𝑉0 ).

Now define two task-force groupings of these teams as 1-superedges:
𝑒 𝐴 := {𝑇1 , 𝑇2 },

𝑒 𝐵 := {𝑇2 , 𝑇3 },

so that

𝐸 := {𝑒 𝐴, 𝑒 𝐵 } ⊆ P2 (𝑉0 ) = P P (𝑉0 ) .
Each superedge is a nonempty set of 1-supervertices, hence (𝑉, 𝐸) is a 1-SuperHyperGraph on the base set 𝑉0 .
Assume that each task force runs with a certain monthly budget (in arbitrary monetary units). We encode these
budgets as a positive weight function
𝑤 : 𝐸 → R>0 ,

𝑤(𝑒 𝐴) := 10,

𝑤(𝑒 𝐵 ) := 6.

Thus 𝑒 𝐴 (linking teams 𝑇1 and 𝑇2 ) has a higher weight and represents a larger, more expensive task force, while
𝑒 𝐵 (linking 𝑇2 and 𝑇3 ) is a smaller one.
The triple
W-SHG (1) := (𝑉, 𝐸, 𝑤)
is a weighted SuperHyperGraph of depth 1. Vertices are teams (subsets of employees), superedges are task
forces (groupings of teams), and weights quantify the intensity or cost of each multi-team collaboration in this
hierarchical setting.

Table 4.7 provides an overview of the comparison of weighted graphs, weighted hypergraphs, and weighted
SuperHyperGraphs.
Table 4.7: Comparison of weighted graphs, weighted hypergraphs, and weighted SuperHyperGraphs
Framework

Underlying structure

Weight assignment

Weighted graph

Simple graph 𝐺 = (𝑉, 𝐸) with pairwise edges 𝑢𝑣 ∈ 𝐸.

Weighted hypergraph

Hypergraph 𝐻 = (𝑉, 𝐸) with hyperedges 𝑒 ∈ 𝐸 ⊆ P∗ (𝑉).

A weight function 𝑤 : 𝐸 → R>0 (and
optionally on 𝑉) assigning a positive
real weight to each edge.
A weight function 𝑤 : 𝐸 → R>0 assigning a positive real weight to each
hyperedge (e.g. cost, capacity, interaction strength).
A weight function 𝑤 : 𝐸 → R>0 assigning a positive real weight to each 𝑛superedge, encoding hierarchical importance or reliability.

Weighted
SuperHyperGraph

𝑛-

𝑛-SuperHyperGraph SHG (𝑛) = (𝑉, 𝐸)
with 𝑉 ⊆ P𝑛 (𝑉0 ) and 𝐸 ⊆ P𝑛+1 (𝑉0 ).

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Chapter 4. Some Particular SuperHyperGraphs 4.11 SuperHyperTree and SuperHypertree Decomposition A SuperHyperTree is an acyclic 𝑛-SuperHyperGraph whose superedges form a join-tree and satisfy the required connectedness conditions for every supervertex in the structure [116,383,384]. A SuperHyperTree generalizes the classical notion of a HyperTree [385–387]. A tree decomposition represents a graph by a tree of vertex-bags so every edge is inside some bag and bags intersect consistently [388, 389]. Tree decomposition is important because many hard graph problems become tractable on bounded treewidth, enabling dynamic programming, efficient algorithms, and structural insights in theory and practice. A SuperHypertree decomposition represents an 𝑛-SuperHyperGraph by means of a tree whose bags and guards guarantee both vertex and edge connectivity throughout the decomposition [383, 384, 390, 391]. SuperHypertree decompositions are closely related to tree-decompositions [389, 392] and Hypertree-decompositions [386, 387]. Definition 4.11.1 (n-SuperHyperTree). [116] Let 𝑉0 be a finite nonempty base set and let 𝑛 ∈ N0 . An 𝑛-SuperHyperGraph is a pair 𝐻 (𝑛) = (𝑉, 𝐸) where • 𝑉 ⊆ 𝑃𝑛 (𝑉0 ) is a finite set of 𝑛-supervertices, and • 𝐸 is a finite family of nonempty subsets of 𝑉, whose elements are called 𝑛-superedges. We say that 𝐻 (𝑛) is an 𝑛-SuperHyperTree if there exists a tree 𝐽 = (𝐸, 𝐹) whose vertex set is 𝐸 (called a join superhypertree of 𝐻 (𝑛) ) such that, for every supervertex 𝑣 ∈ 𝑉, the set 𝐽𝑣 := { 𝑒 ∈ 𝐸 | 𝑣 ∈ 𝑒 } ⊆ 𝑉 (𝐽) is nonempty and induces a connected subtree of 𝐽. In this case, the 𝑛-SuperHyperGraph 𝐻 (𝑛) is called acyclic (or join-tree acyclic) and 𝐽 is a join superhypertree of 𝐻 (𝑛) . Example 4.11.2 (A simple 2-SuperHyperTree). Let the finite base set be 𝑉0 := {𝑎, 𝑏, 𝑐}. Define 𝑃0 (𝑉0 ) := 𝑉0 , 𝑃1 (𝑉0 ) := 𝑃(𝑉0 ), 𝑃2 (𝑉0 ) := 𝑃 𝑃(𝑉0 ) , and consider the following 2-supervertices (each is a nonempty subset of 𝑃1 (𝑉0 )): 𝑣 1 := {{𝑎}, {𝑎, 𝑏}}, 𝑣 2 := {{𝑏}, {𝑏, 𝑐}}, 𝑣 3 := {{𝑐}, {𝑎, 𝑐}}, 𝑣 4 := {{𝑎, 𝑏, 𝑐}}. Put 𝑉 := {𝑣 1 , 𝑣 2 , 𝑣 3 , 𝑣 4 } ⊆ 𝑃2 (𝑉0 ), and define three 2-superedges 𝑒 1 := {𝑣 1 , 𝑣 2 }, 𝑒 2 := {𝑣 2 , 𝑣 3 }, so that 𝐸 := {𝑒 1 , 𝑒 2 , 𝑒 3 }. Then 𝐻 (2) := (𝑉, 𝐸) is a 2-SuperHyperGraph in the sense of the above definition. Consider the graph 𝐽 := (𝐸, 𝐹), 78 𝑒 3 := {𝑣 3 , 𝑣 4 },

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Chapter 4. Some Particular SuperHyperGraphs where the vertex set is 𝐸 = {𝑒 1 , 𝑒 2 , 𝑒 3 } and the edge set is 𝐹 := {𝑒 1 , 𝑒 2 }, {𝑒 2 , 𝑒 3 } . Thus 𝐽 is a path 𝑒 1 − 𝑒 2 − 𝑒 3 , hence a tree. For each 2-supervertex 𝑣 ∈ 𝑉 we have: 𝐽𝑣1 = {𝑒 1 }, 𝐽𝑣2 = {𝑒 1 , 𝑒 2 }, 𝐽𝑣3 = {𝑒 2 , 𝑒 3 }, 𝐽𝑣4 = {𝑒 3 }. Each 𝐽𝑣𝑖 is nonempty and induces a connected subtree of 𝐽 (a single vertex or a path of length one). Hence 𝐻 (2) is a 2-SuperHyperTree, and 𝐽 is a join superhypertree of 𝐻 (2) . We describe below how to present the definitions of hypertree decompositions and superhypertree decompositions. Moreover, several concepts related to tree-width are known in the literature, including branchwidth [393, 394], linear-width [395], path-distance-width [396], clique-width [397, 398], and sim-width [399]. Intuitively speaking, without fear of misunderstanding, these can be regarded as graph parameters that measure how close a given graph is to the desired structure. These are often referred to as graph width parameters, and relationships among different graph width parameters, as well as comparisons with other graph parameters, are frequently studied. Definition 4.11.3 (Tree decomposition and treewidth). [400,401] Let 𝐺 = (𝑉, 𝐸) be a finite undirected graph. A tree decomposition of 𝐺 is a pair (𝑇, 𝜒) where 𝑇 = (𝑁, 𝐹) is a tree and 𝜒 is a mapping assigning to each node 𝑝 ∈ 𝑁 a set (called a bag) 𝜒( 𝑝) ⊆ 𝑉, such that the following conditions hold: 1. Vertex coverage. For every vertex 𝑣 ∈ 𝑉 there exists a node 𝑝 ∈ 𝑁 with 𝑣 ∈ 𝜒( 𝑝). 2. Edge coverage. For every edge {𝑢, 𝑣} ∈ 𝐸 there exists a node 𝑝 ∈ 𝑁 with {𝑢, 𝑣} ⊆ 𝜒( 𝑝). 3. Running intersection (connectedness). For every vertex 𝑣 ∈ 𝑉, the set of nodes 𝑁 𝑣 := { 𝑝 ∈ 𝑁 | 𝑣 ∈ 𝜒( 𝑝) } induces a connected subtree of 𝑇. The width of (𝑇, 𝜒) is width(𝑇, 𝜒) := max | 𝜒( 𝑝)| − 1 . 𝑝∈ 𝑁 The treewidth of 𝐺 is tw(𝐺) := min{width(𝑇, 𝜒) | (𝑇, 𝜒) is a tree decomposition of 𝐺}. Definition 4.11.4 (Hypertree decomposition (HyperTree-Decomposition)). [386, 387, 402] Let 𝐻 = (𝑉, 𝐸) be a finite hypergraph, where 𝑉 = var(𝐻) is the set of variables (vertices) and 𝐸 = edges(𝐻) is the set of hyperedges. A hypertree decomposition of 𝐻 is a triple 𝐻𝐷 = ⟨𝑇, 𝜒, 𝜆⟩, where 𝑇 is a rooted tree, and 𝜒 and 𝜆 are labeling functions such that, for every node 𝑝 ∈ 𝑉 (𝑇), 𝜒( 𝑝) ⊆ 𝑉 𝜆( 𝑝) ⊆ 𝐸 . and For any F ⊆ 𝐸, write var(F ) := Ø ℎ ⊆ 𝑉. ℎ∈ F For any node 𝑝 ∈ 𝑉 (𝑇), let 𝑇 𝑝 denote the subtree of 𝑇 rooted at 𝑝, and set Ø 𝜒(𝑇 𝑝 ) := 𝜒(𝑞). 𝑞∈𝑉 (𝑇𝑝 ) The triple ⟨𝑇, 𝜒, 𝜆⟩ is a hypertree decomposition of 𝐻 if it satisfies all of the following conditions: 79

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Chapter 4. Some Particular SuperHyperGraphs (1) (Edge coverage) For each hyperedge ℎ ∈ 𝐸, there exists a node 𝑝 ∈ 𝑉 (𝑇) such that ℎ ⊆ 𝜒( 𝑝). (2) (Connectedness of variables) For each variable 𝑌 ∈ 𝑉, the set { 𝑝 ∈ 𝑉 (𝑇) | 𝑌 ∈ 𝜒( 𝑝) } induces a connected subtree of 𝑇. (3) (Local covering by guards) For each node 𝑝 ∈ 𝑉 (𝑇), 𝜒( 𝑝) ⊆ var(𝜆( 𝑝)). (4) (Special condition / descendant separation) For each node 𝑝 ∈ 𝑉 (𝑇), var(𝜆( 𝑝)) ∩ 𝜒(𝑇 𝑝 ) ⊆ 𝜒( 𝑝). The width of 𝐻𝐷 is width(𝐻𝐷) := max |𝜆( 𝑝)|. 𝑝∈𝑉 (𝑇 ) Definition 4.11.5 (SuperHypertree decomposition of an 𝑛-SuperHyperGraph). Let 𝐻 (𝑛) = (𝑉, 𝐸) be a finite 𝑛-SuperHyperGraph. A SuperHypertree decomposition of 𝐻 (𝑛) is a triple (𝑇, B, C), where • 𝑇 = (𝑉𝑇 , 𝐸𝑇 ) is a finite tree, • B = { 𝐵𝑡 ⊆ 𝑉 | 𝑡 ∈ 𝑉𝑇 } is a family of bags, • C = { 𝐶𝑡 ⊆ 𝐸 | 𝑡 ∈ 𝑉𝑇 } is a family of guards, such that the following conditions hold. (1) Vertex coverage. Every supervertex appears in at least one bag: Ø 𝑉 = 𝐵𝑡 . 𝑡 ∈𝑉𝑇 (2) Superedge coverage. For every superedge 𝑒 ∈ 𝐸 there exists 𝑡 ∈ 𝑉𝑇 with 𝑒 ⊆ 𝐵𝑡 . (3) Vertex connectedness. For every supervertex 𝑣 ∈ 𝑉, the set 𝑇𝑣 := { 𝑡 ∈ 𝑉𝑇 | 𝑣 ∈ 𝐵𝑡 } is nonempty and induces a connected subtree of 𝑇. (4) Guard covering. For each 𝑡 ∈ 𝑉𝑇 , the union of the superedges in 𝐶𝑡 covers the bag 𝐵𝑡 , that is Ø 𝐵𝑡 ⊆ 𝑒. 𝑒∈𝐶𝑡 (5) Guard connectedness and consistency. For every superedge 𝑒 ∈ 𝐸, the set 𝑇𝑒 := { 𝑡 ∈ 𝑉𝑇 | 𝑒 ∈ 𝐶𝑡 } is nonempty and induces a connected subtree of 𝑇, and whenever 𝑒 ⊆ 𝐵𝑡 holds for some 𝑡 ∈ 𝑉𝑇 , we also have 𝑒 ∈ 𝐶𝑡 . 80

82.

Chapter 4. Some Particular SuperHyperGraphs In this situation we say that (𝑇, B, C) is a SuperHypertree decomposition of the 𝑛-SuperHyperGraph 𝐻 (𝑛) . Example 4.11.6 (A SuperHypertree decomposition of a 2-SuperHyperGraph). We continue with the 2SuperHyperGraph 𝐻 (2) = (𝑉, 𝐸) from the previous example, where 𝑉 = {𝑣 1 , 𝑣 2 , 𝑣 3 , 𝑣 4 } and 𝐸 = {𝑒 1 , 𝑒 2 , 𝑒 3 } with 𝑒 1 = {𝑣 1 , 𝑣 2 }, 𝑒 2 = {𝑣 2 , 𝑣 3 }, 𝑒 3 = {𝑣 3 , 𝑣 4 }. Define a tree 𝑇 = (𝑉𝑇 , 𝐸𝑇 ) by 𝐸𝑇 := {𝑡 1 , 𝑡2 }, {𝑡 2 , 𝑡3 } , 𝑉𝑇 := {𝑡 1 , 𝑡2 , 𝑡3 }, so 𝑇 is again a path 𝑡1 − 𝑡2 − 𝑡3 . Define the family of bags B = {𝐵𝑡1 , 𝐵𝑡2 , 𝐵𝑡3 } by 𝐵𝑡1 := 𝑒 1 = {𝑣 1 , 𝑣 2 }, 𝐵𝑡2 := 𝑒 2 = {𝑣 2 , 𝑣 3 }, 𝐵𝑡3 := 𝑒 3 = {𝑣 3 , 𝑣 4 }, and the family of guards C = {𝐶𝑡1 , 𝐶𝑡2 , 𝐶𝑡3 } by 𝐶𝑡1 := {𝑒 1 }, 𝐶𝑡2 := {𝑒 2 }, 𝐶𝑡3 := {𝑒 3 }. We now verify the conditions of a SuperHypertree decomposition: • Vertex coverage: Ø 𝐵𝑡 = 𝐵𝑡1 ∪ 𝐵𝑡2 ∪ 𝐵𝑡3 = {𝑣 1 , 𝑣 2 , 𝑣 3 , 𝑣 4 } = 𝑉 . 𝑡 ∈𝑉𝑇 • Superedge coverage: For each 𝑒 𝑖 ∈ 𝐸 we have 𝑒 𝑖 = 𝐵𝑡𝑖 , hence 𝑒 𝑖 ⊆ 𝐵𝑡𝑖 . • Vertex connectedness: For each 𝑣 ∈ 𝑉, 𝑇𝑣1 = {𝑡1 }, 𝑇𝑣2 = {𝑡 1 , 𝑡2 }, 𝑇𝑣3 = {𝑡2 , 𝑡3 }, 𝑇𝑣4 = {𝑡3 }, each inducing a connected subtree of 𝑇. • Guard covering: For each 𝑡𝑖 , Ø 𝑒 = 𝑒 𝑖 = 𝐵𝑡𝑖 , 𝑒∈𝐶𝑡𝑖 so 𝐵𝑡𝑖 ⊆ Ð 𝑒∈𝐶𝑡𝑖 𝑒 holds. • Guard connectedness and consistency: For each superedge 𝑒 𝑖 ∈ 𝐸, 𝑇𝑒𝑖 := {𝑡 ∈ 𝑉𝑇 | 𝑒 𝑖 ∈ 𝐶𝑡 } = {𝑡𝑖 }, which is nonempty and connected. Moreover, whenever 𝑒 𝑖 ⊆ 𝐵𝑡 , we have 𝑡 = 𝑡 𝑖 and thus 𝑒 𝑖 ∈ 𝐶𝑡𝑖 by definition. Therefore, (𝑇, B, C) is a SuperHypertree decomposition of the 2-SuperHyperGraph 𝐻 (2) . Table 4.8 presents a concise overview of tree, hypertree, and superhypertree decompositions. 81

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Chapter 4. Some Particular SuperHyperGraphs
Decomposition
Input object
Tree
decomposi- Graph 𝐺 = (𝑉 , 𝐸 )
tion [400, 401]

Structure and labels
Key constraints (informal)
Ð
Tree 𝑇 with bags 𝜒 ( 𝑝) ⊆ 𝑉 for 𝑝 ∈ (i) 𝑝 𝜒 ( 𝑝) = 𝑉 ;
𝑉 (𝑇 )
(ii) ∀ {𝑢, 𝑣 } ∈ 𝐸 ∃ 𝑝 : {𝑢, 𝑣 } ⊆ 𝜒 ( 𝑝) ;
(iii) { 𝑝 | 𝑣 ∈ 𝜒 ( 𝑝) } is connected in 𝑇
Hypertree decomposi- Hypergraph 𝐻 = Rooted tree 𝑇 with bags 𝜒 ( 𝑝) ⊆ 𝑉 and (i) ∀ℎ ∈ 𝐸 ∃ 𝑝 : ℎ ⊆ 𝜒 ( 𝑝) ;
tion [386, 387, 402]
(𝑉 , 𝐸 )
guards 𝜆( 𝑝) ⊆ 𝐸
(ii) { 𝑝 | 𝑣 ∈ 𝜒 ( 𝑝) } is connected;
(iii) 𝜒 ( 𝑝) ⊆ var(𝜆( 𝑝) ) ;
(iv) var(𝜆( 𝑝) ) ∩ 𝜒 (𝑇𝑝 ) ⊆ 𝜒 ( 𝑝)
Ð
SuperHypertree decom- 𝑛-SuperHyperGraph Tree 𝑇 with bags 𝐵𝑡 ⊆ 𝑉 and guards 𝐶𝑡 ⊆ (i) 𝑡 𝐵𝑡 = 𝑉 ;
(𝑛)
position [383, 384, 391] 𝐻
𝐸
(ii) ∀𝑒 ∈ 𝐸 ∃𝑡 : 𝑒 ⊆ 𝐵𝑡 ;
= (𝑉 , 𝐸 )
(iii) {𝑡 | 𝑣 Ð
∈ 𝐵𝑡 } is connected;
(iv) 𝐵𝑡 ⊆ 𝑒∈𝐶𝑡 𝑒;
(v) {𝑡 | 𝑒 ∈ 𝐶𝑡 } connected and (𝑒 ⊆
𝐵𝑡 ⇒ 𝑒 ∈ 𝐶𝑡 )

Typical width
max
 𝑝 | 𝜒 ( 𝑝) | −
1

max 𝑝 |𝜆( 𝑝) |

max𝑡 |𝐶𝑡 |

Table 4.8: Concise overview of tree, hypertree, and superhypertree decompositions.

4.12

Complete 𝑛-SuperHyperGraph

A complete graph is a simple undirected graph in which every pair of distinct vertices is joined by exactly
one edge [403–405]. As concepts related to complete graphs, notions such as complete digraphs [406, 407],
bicomplete graphs [408], complete fuzzy graphs [409, 410], complete multipartite graph [411, 412], complete
bipartite graph [413, 414], random complete graph [415], probe complete graphs [416, 417], and complete
neutrosophic graphs [418, 419] are well known. Complete graphs serve as fundamental extremal objects: they
often bound chromatic number [420], clique number [421], and density, underpin Ramsey theory, minors, and
worst-case algorithmic complexity analyses.
A complete hypergraph is a hypergraph whose hyperedges consist of all nonempty vertex subsets, so every
possible multiway connection appears [422–424]. A complete 𝑛-SuperHyperGraph is an 𝑛-SuperHyperGraph
where every nonempty subset of 𝑛-supervertices forms an 𝑛-superedge, realizing all hierarchical relations.
Definition 4.12.1 (Complete hypergraph). [422–424] Let 𝑉 be a finite vertex set with |𝑉 | = 𝑛.
(1) The complete 𝑘-uniform hypergraph on 𝑉 is the hypergraph
 
𝑉
𝐾𝑛(𝑘 ) := (𝑉, 𝐸),
𝐸 :=
:= { 𝑒 ⊆ 𝑉 | |𝑒| = 𝑘 }.
𝑘
(2) The (non-uniform) complete hypergraph on 𝑉 is the hypergraph
𝑛  
Ø
𝑉
.
𝐾𝑛 := (𝑉, 𝐸),
𝐸 :=
𝑘
𝑘=2
Definition 4.12.2 (Complete 𝑛-SuperHyperGraph). Let 𝑉0 be a nonempty finite base set and let 𝑛 ∈ N0 . Recall
that the iterated powersets are defined by

P0 (𝑉0 ) := 𝑉0 ,
P 𝑘+1 (𝑉0 ) := P P 𝑘 (𝑉0 ) (𝑘 ≥ 0),
where P(𝑋) denotes the powerset of a set 𝑋.
A level-𝑛 SuperHyperGraph on 𝑉0 is a pair
SHG (𝑛) = (𝑉𝑛 , 𝐸),
where
∅ ≠ 𝑉𝑛 ⊆ P𝑛 (𝑉0 )

and

∅ ≠ 𝐸 ⊆ P(𝑉𝑛 ) \ {∅}.

The elements of 𝑉𝑛 are called 𝑛-supervertices and the elements of 𝐸 are called 𝑛-superedges.
The level-𝑛 SuperHyperGraph SHG (𝑛) = (𝑉𝑛 , 𝐸) is called a complete 𝑛-SuperHyperGraph if
𝐸 = P(𝑉𝑛 ) \ {∅},
that is, every nonempty subset of 𝑉𝑛 occurs as an 𝑛-superedge.
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Chapter 4. Some Particular SuperHyperGraphs
Equivalently, SHG (𝑛) is complete if and only if for every nonempty family 𝐹 ⊆ 𝑉𝑛 there exists a unique 𝑒 ∈ 𝐸
with 𝑒 = 𝐹.
For 1 ≤ 𝑘 ≤ |𝑉𝑛 |, a complete 𝑛-SuperHyperGraph is called 𝑘-uniform if all its 𝑛-superedges have cardinality
𝑘; in this case
𝐸 = { 𝐹 ⊆ 𝑉𝑛 | |𝐹 | = 𝑘 }.
When 𝑛 = 0, this definition reduces to the usual notions of complete hypergraph and complete 𝑘-uniform
hypergraph on the vertex set 𝑉0 .
Example 4.12.3 (A complete 1-SuperHyperGraph on three supervertices). Let the finite base set be
𝑉0 := {𝑎, 𝑏, 𝑐}.
Then
P0 (𝑉0 ) = 𝑉0 ,

P1 (𝑉0 ) = P(𝑉0 ).

Choose three 1-supervertices
𝑣 1 := {𝑎},

𝑣 2 := {𝑏},

𝑣 3 := {𝑎, 𝑏},

and set
𝑉1 := {𝑣 1 , 𝑣 2 , 𝑣 3 } ⊆ P1 (𝑉0 ).
We now define the family of 1-superedges by taking all nonempty subsets of 𝑉1 :

𝐸 := P(𝑉1 ) \ {∅} = {𝑣 1 }, {𝑣 2 }, {𝑣 3 }, {𝑣 1 , 𝑣 2 }, {𝑣 1 , 𝑣 3 }, {𝑣 2 , 𝑣 3 }, {𝑣 1 , 𝑣 2 , 𝑣 3 } .
Then
SHG (1) := (𝑉1 , 𝐸)
is a level-1 SuperHyperGraph on the base set 𝑉0 . Moreover, by construction we have
𝐸 = P(𝑉1 ) \ {∅},
so every nonempty subset of 𝑉1 appears as a 1-superedge. Hence SHG (1) is a complete 1-SuperHyperGraph
in the sense of the above definition.

4.13

co-SuperHyperGraph

A co-graph is a graph obtained from 𝐾1 by repeatedly applying disjoint union and complementation; equivalently, it is 𝑃4 -free [425–427]. A co-hypergraph is a pair (𝑋, A) where 𝑋 is a nonempty vertex set and
A ⊆ P∗ (𝑋) is a family of nonempty subsets of 𝑋 (co-edges), typically with | 𝐴| ≥ 2 for all 𝐴 ∈ A [428–430].
A co-𝑛-superhypergraph is a tuple (𝑉, A1 , . . . , A 𝑛 ) with A1 ⊆ P∗ (𝑉) and A𝑖 ⊆ A2𝑖−1 for every 2 ≤ 𝑖 ≤ 𝑛, so
level-𝑖 co-links connect pairs of level-(𝑖 − 1) objects.
Definition 4.13.1 (Graph complement). Let 𝐺 = (𝑉, 𝐸) be a finite simple undirected graph. Its complement
is 𝐺 = (𝑉, 𝐸), where

𝐸 := {𝑢, 𝑣} ⊆ 𝑉 | 𝑢 ≠ 𝑣, {𝑢, 𝑣} ∉ 𝐸 .
Definition 4.13.2 (Co-graph (cograph)). A (finite simple) graph 𝐺 is a co-graph (also called a cograph) if it
belongs to the smallest class C of graphs satisfying:
1. 𝐾1 ∈ C.
¤ ∈ C.
2. If 𝐺, 𝐻 ∈ C, then their disjoint union 𝐺 ∪𝐻
3. If 𝐺 ∈ C, then 𝐺 ∈ C.
83

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Chapter 4. Some Particular SuperHyperGraphs Equivalently, 𝐺 is a cograph if and only if 𝐺 has no induced path on four vertices (𝑃4 -free). Example 4.13.3 (A co-graph (cograph)). Let 𝑉 = {1, 2, 3, 4}. Start from four isolated vertices 𝐾1 and take the disjoint union 𝐺 0 := 𝐾1 ∪¤ 𝐾1 ∪¤ 𝐾1 ∪¤ 𝐾1 , so 𝐸 (𝐺 0 ) = ∅. Now take the complement: 𝐺 := 𝐺 0 = 𝐾4 . Since 𝐺 is obtained from 𝐾1 using disjoint union and complement, 𝐺 is a co-graph. (Equivalently, 𝐾4 contains no induced 𝑃4 .) Definition 4.13.4 (Co-hypergraph (co-edge hypergraph)). Let 𝑋 be a finite nonempty set and let P∗ (𝑋) := P (𝑋) \ {∅}. A co-hypergraph is a pair 𝐻 = (𝑋, A), where A ⊆ P∗ (𝑋) is a family of nonempty subsets of 𝑋 (typically one assumes | 𝐴| ≥ 2 for all 𝐴 ∈ A). The members of A are called co-edges. Example 4.13.5 (A co-graph (cograph)). Let 𝑉 = {1, 2, 3, 4}. Start from four isolated vertices 𝐾1 and take the disjoint union 𝐺 0 := 𝐾1 ∪¤ 𝐾1 ∪¤ 𝐾1 ∪¤ 𝐾1 , so 𝐸 (𝐺 0 ) = ∅. Now take the complement: 𝐺 := 𝐺 0 = 𝐾4 . Since 𝐺 is obtained from 𝐾1 using disjoint union and complement, 𝐺 is a co-graph. (Equivalently, 𝐾4 contains no induced 𝑃4 .) Definition 4.13.6 (Co-𝑛-superhypergraph). Fix an integer 𝑛 ≥ 1 and a finite nonempty vertex set 𝑉. A co-𝑛-superhypergraph is a tuple S co = 𝑉, A1 , A2 , . . . , A 𝑛 such that ∗ A1 ⊆ P (𝑉) and A𝑖−1 A𝑖 ⊆ 2 for every 2 ≤ 𝑖 ≤ 𝑛. Elements of A1 are level-1 co-edges, and elements of A𝑖 (𝑖 ≥ 2) are level-𝑖 co-superlinks, i.e., unordered links between two distinct level-(𝑖 − 1) objects. Remark 4.13.7 (2-uniform case). If A1 ⊆ 𝑉2 , then (𝑉, A1 ) can be identified with the simple graph 𝐺 = (𝑉, 𝐸) where 𝐸 = A1 . Example 4.13.8 (A co-hypergraph). Let 𝑋 := {𝑎, 𝑏, 𝑐, 𝑑}, A := {𝑎, 𝑏}, {𝑏, 𝑐, 𝑑} ⊆ P∗ (𝑋). Then the pair H := (𝑋, A) is a co-hypergraph: its vertices are 𝑋 and its co-edges are the nonempty subsets in A (and each has size at least 2, so there are no loops). Theorem 4.13.9 (Co-𝑛-superhypergraphs generalize co-hypergraphs and co-graphs). Fix 𝑛 ≥ 1. 84

86.

Chapter 4. Some Particular SuperHyperGraphs 1. (Co-hypergraphs embed.) For every co-hypergraph 𝐻 = (𝑋, A), the tuple S co (𝐻) := 𝑋, A, ∅, . . . , ∅ is a co-𝑛-superhypergraph. 2. (Co-graphs embed.) For every co-graph (cograph) 𝐺 = (𝑉, 𝐸), the tuple S co (𝐺) := 𝑉, 𝐸, ∅, . . . , ∅ is a co-𝑛-superhypergraph (with A1 = 𝐸 ⊆ 𝑉 ∗ 2 ⊆ P (𝑉)). Hence the framework of co-𝑛-superhypergraphs contains both co-hypergraphs and co-graphs as special cases. Proof. (1) Let 𝐻 = (𝑋, A) be a co-hypergraph. Set A1 := A and A𝑖 := ∅ for 2 ≤ 𝑖 ≤ 𝑛. Then A1 ⊆ P∗ (𝑋) A𝑖−1 holds by definition trivially. Therefore 2 of co-hypergraph. For every 𝑖 ≥ 2, we have A𝑖 = ∅ ⊆ 𝑋, A1 , . . . , A 𝑛 is a co-𝑛-superhypergraph. (2) Let 𝐺 = (𝑉, 𝐸) be a co-graph (cograph). Since 𝐺 is a simple graph, every edge is a 2-element subset of 𝑉, i.e., 𝐸 ⊆ 𝑉2 ⊆ P∗ (𝑉). Define A1 := 𝐸 and A𝑖 := ∅ for 2 ≤ 𝑖 ≤ 𝑛. As in (1), the level conditions for a co-𝑛-superhypergraph hold: A1 ⊆ P∗ (𝑉) and A𝑖 = ∅ ⊆ A2𝑖−1 for 𝑖 ≥ 2. Hence 𝑉, 𝐸, ∅, . . . , ∅ is a co-𝑛-superhypergraph. This proves both embeddings, so co-𝑛-superhypergraphs generalize co-hypergraphs and co-graphs in the sense of containing them as special cases. □ 4.14 Perfect SuperHyperGraphs A perfect graph is a graph in which every induced subgraph satisfies 𝜒 = 𝜔, i.e., the chromatic number equals the clique number [431–434]. Related notions include superperfect graphs [435], perfect fuzzy graphs [436–438], strongly perfect graphs [431, 433], locally perfect graphs [439], and line perfect graphs [440, 441]. A perfect hypergraph is a hypergraph whose shadow (2-section) graph is perfect, so every induced subhypergraph’s shadow satisfies 𝜒 = 𝜔. A perfect superhypergraph is a superhypergraph such that all level interaction graphs of every induced substructure are perfect, hence 𝜒 = 𝜔 at every level. Definition 4.14.1 (Perfect graph). [431–434] A (finite, simple) graph 𝐺 = (𝑉, 𝐸) is perfect if for every induced subgraph 𝐻 = 𝐺 [𝑈] with 𝑈 ⊆ 𝑉 we have 𝜒(𝐻) = 𝜔(𝐻), where 𝜒(𝐻) is the chromatic number of 𝐻, and 𝜔(𝐻) is the clique number of 𝐻. Definition 4.14.2 (Hypergraph, induced subhypergraph, and shadow graph). A (finite) hypergraph is a pair 𝐻 = (𝑉, E) where 𝑉 is a finite set and ∅ ∉ E ⊆ P (𝑉). For 𝑈 ⊆ 𝑉, the induced subhypergraph is 𝐻 [𝑈] := 𝑈, E [𝑈] , E [𝑈] := { 𝑒 ∈ E | 𝑒 ⊆ 𝑈 }. The shadow graph (also called the 2-section) of 𝐻 is the simple graph 𝜕 (𝐻) := 𝑉, {𝑢, 𝑣} ⊆ 𝑉 : 𝑢 ≠ 𝑣, ∃𝑒 ∈ E with {𝑢, 𝑣} ⊆ 𝑒 . Definition 4.14.3 (Perfect hypergraph (shadow-perfect)). A hypergraph 𝐻 is perfect if its shadow graph 𝜕 (𝐻) is a perfect graph. Equivalently, 𝐻 is perfect if for every 𝑈 ⊆ 𝑉 (𝐻), 𝜒 𝜕 (𝐻 [𝑈]) = 𝜔 𝜕 (𝐻 [𝑈]) . 85

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Chapter 4. Some Particular SuperHyperGraphs Example 4.14.4 (A perfect hypergraph (shadow-perfect)). Let 𝑉 := {1, 2, 3, 4}, E := {1, 2, 3}, {2, 3, 4} ⊆ P∗ (𝑉). Define the hypergraph 𝐻 := (𝑉, E). Its shadow graph 𝜕 (𝐻) has an edge {𝑢, 𝑣} iff 𝑢 ≠ 𝑣 and {𝑢, 𝑣} ⊆ 𝑒 for some 𝑒 ∈ E. Since {1, 2, 3} induces 𝐾3 on {1, 2, 3} and {2, 3, 4} induces 𝐾3 on {2, 3, 4}, we obtain 𝐸 𝜕 (𝐻) = {1, 2}, {1, 3}, {2, 3}, {2, 4}, {3, 4} . Thus 𝜕 (𝐻) is exactly the graph 𝐾4 with the single missing edge {1, 4}. We verify the perfectness condition: 𝜔 𝜕 (𝐻) = 3 (for example, {1, 2, 3} is a clique), and a proper 3-coloring is 𝑐(2) = 1, 𝑐(3) = 2, 𝑐(1) = 3, 𝑐(4) = 3, so 𝜒 𝜕 (𝐻) ≤ 3. Because 𝜒 ≥ 𝜔 holds for every graph, we get 𝜒 𝜕 (𝐻) = 𝜔 𝜕 (𝐻) = 3. Moreover, for every 𝑈 ⊆ 𝑉, the induced subgraph 𝜕 (𝐻) [𝑈] is either a clique or a subgraph of this 𝐾4 -minusone-edge, hence again satisfies 𝜒 = 𝜔 (one checks directly for |𝑈| ≤ 4). Therefore 𝐻 is a perfect hypergraph in the shadow-perfect sense. Definition 4.14.5 (𝑛-SuperHyperGraph via iterated super-links). Fix an integer 𝑛 ≥ 1 and a finite base vertex set 𝑉. An 𝑛-SuperHyperGraph is a tuple S = 𝑉, E1 , E2 , . . . , E 𝑛 such that ∗ E1 ⊆ P (𝑉) and E𝑖−1 E𝑖 ⊆ 2 for every 2 ≤ 𝑖 ≤ 𝑛, where P∗ (𝑋) := P (𝑋) \ {∅} and 𝑋2 := {{𝑎, 𝑏} ⊆ 𝑋 : 𝑎 ≠ 𝑏}. Elements of E1 are hyperedges, and elements of E𝑖 (𝑖 ≥ 2) are level-𝑖 super-links (unordered links between two distinct level-(𝑖 − 1) objects). For 𝑛 = 1, S is exactly a hypergraph (𝑉, E1 ). Definition 4.14.6 (Induced sub-𝑛-SuperHyperGraph). Let S = (𝑉, E1 , . . . , E 𝑛 ) be an 𝑛-SuperHyperGraph and let 𝑈 ⊆ 𝑉. Define recursively: E1 [𝑈] := { 𝑒 ∈ E1 : 𝑒 ⊆ 𝑈 }, E𝑖 [𝑈] := { 𝜆 ∈ E𝑖 : 𝜆 ⊆ E𝑖−1 [𝑈] } (2 ≤ 𝑖 ≤ 𝑛). Then S [𝑈] := 𝑈, E1 [𝑈], . . . , E 𝑛 [𝑈] is called the induced sub-𝑛-SuperHyperGraph on 𝑈. Definition 4.14.7 (Level interaction graphs of an 𝑛-SuperHyperGraph). Let S = (𝑉, E1 , . . . , E 𝑛 ) be an 𝑛SuperHyperGraph. (0) The level-0 interaction graph is the shadow graph of (𝑉, E1 ): 𝐺 0 (S) := 𝜕 (𝑉, E1 ) . (i) For each 1 ≤ 𝑖 ≤ 𝑛 − 1, the level-𝑖 interaction graph is the simple graph 𝐺 𝑖 (S) := E𝑖 , 𝐸 𝑖link , 𝐸 𝑖link := {𝐴, 𝐵} ⊆ E𝑖 : {𝐴, 𝐵} ∈ E𝑖+1 . 86

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Chapter 4. Some Particular SuperHyperGraphs
Definition 4.14.8 (Perfect 𝑛-SuperHyperGraph). An 𝑛-SuperHyperGraph S is perfect if for every subset 𝑈 ⊆ 𝑉
and every 𝑖 ∈ {0, 1, . . . , 𝑛 − 1},


𝜒 𝐺 𝑖 (S [𝑈]) = 𝜔 𝐺 𝑖 (S [𝑈]) .
Example 4.14.9 (A perfect 2-SuperHyperGraph). Let
𝑉 := {1, 2, 3, 4}.
Define level-1 hyperedges
E1 := {𝑒 1 , 𝑒 2 },

𝑒 1 := {1, 2, 3}, 𝑒 2 := {2, 3, 4}.

Define level-2 super-links by
 

E1
E2 := {𝑒 1 , 𝑒 2 } ⊆
.
2
Then
S := (𝑉, E1 , E2 )
is a 2-SuperHyperGraph.
We check perfectness of S under your definition.
Level 0 interaction graph. By definition,

𝐺 0 (S) = 𝜕 (𝑉, E1 ) = 𝜕 (𝐻),
where 𝐻 = (𝑉, E1 ) is exactly the hypergraph from the previous example. Hence


𝜒 𝐺 0 (S [𝑈]) = 𝜔 𝐺 0 (S [𝑈]) for all 𝑈 ⊆ 𝑉 .

Level 1 interaction graph. Here the vertex set is E1 = {𝑒 1 , 𝑒 2 } and


𝐸 1link = {𝐴, 𝐵} ⊆ E1 : {𝐴, 𝐵} ∈ E2 = {𝑒 1 , 𝑒 2 } .
Thus
𝐺 1 (S)  𝐾2 ,
so

𝜒 𝐺 1 (S) = 2,


𝜔 𝐺 1 (S) = 2.

For an induced sub-2-SuperHyperGraph S [𝑈], either:
• E1 [𝑈] = ∅ or {𝑒 1 } or {𝑒 2 }, in which case 𝐺 1 (S [𝑈]) has at most one vertex, hence 𝜒 = 𝜔 = 0 or 1; or
• E1 [𝑈] = {𝑒 1 , 𝑒 2 }, which forces 𝑈 = 𝑉, and we are back to 𝐾2 with 𝜒 = 𝜔 = 2.
Therefore,


𝜒 𝐺 1 (S [𝑈]) = 𝜔 𝐺 1 (S [𝑈])

for all 𝑈 ⊆ 𝑉 .

We have verified that for every 𝑈 ⊆ 𝑉 and each 𝑖 ∈ {0, 1},


𝜒 𝐺 𝑖 (S [𝑈]) = 𝜔 𝐺 𝑖 (S [𝑈]) .
Hence S is a perfect 2-SuperHyperGraph.
Lemma 4.14.10 (Induced compatibility of level graphs). Let S be an 𝑛-SuperHyperGraph and 𝑈 ⊆ 𝑉. Then,
for each 𝑖 ∈ {0, 1, . . . , 𝑛 − 1}, the graph 𝐺 𝑖 (S [𝑈]) is an induced subgraph of 𝐺 𝑖 (S).
87

89.

Chapter 4. Some Particular SuperHyperGraphs Proof. For 𝑖 = 0, by definition 𝐺 0 (S [𝑈]) = 𝜕 (𝑈, E1 [𝑈]) , so its vertex set is 𝑈 and its edges are exactly those pairs {𝑢, 𝑣} ⊆ 𝑈 that lie in some 𝑒 ∈ E1 with 𝑒 ⊆ 𝑈. This is precisely the induced subgraph of 𝜕 ((𝑉, E1 )) on 𝑈, i.e. 𝐺 0 (S) [𝑈]. For 1 ≤ 𝑖 ≤ 𝑛 − 1, the vertex set of 𝐺 𝑖 (S [𝑈]) is E𝑖 [𝑈] ⊆ E𝑖 . Moreover, {𝐴, 𝐵} ∈ 𝐸 𝑖link (S [𝑈]) ⇐⇒ { 𝐴, 𝐵} ∈ E𝑖+1 [𝑈] ⇐⇒ { 𝐴, 𝐵} ∈ E𝑖+1 , with 𝐴, 𝐵 ∈ E𝑖 [𝑈]. Hence adjacency in 𝐺 𝑖 (S [𝑈]) is exactly adjacency in 𝐺 𝑖 (S) restricted to E𝑖 [𝑈], i.e. 𝐺 𝑖 (S [𝑈]) is an induced subgraph of 𝐺 𝑖 (S). □ Theorem 4.14.11 (Perfect superhypergraphs generalize perfect hypergraphs and perfect graphs). Fix 𝑛 ≥ 1. 1. (Hypergraph case) Let 𝐻 = (𝑉, E) be a hypergraph. Define an 𝑛-SuperHyperGraph S𝐻 := 𝑉, E1 , E2 , . . . , E 𝑛 by E1 := E, E2 = · · · = E 𝑛 := ∅. Then 𝐻 is a perfect hypergraph if and only if S𝐻 is a perfect 𝑛-SuperHyperGraph. 2. (Graph case) Let 𝐺 = (𝑉, 𝐸) be a (finite, simple) graph and define the 2-uniform hypergraph 𝐻𝐺 := (𝑉, E), E := {{𝑢, 𝑣} : {𝑢, 𝑣} ∈ 𝐸 }. Form S𝐻𝐺 as in (1). Then 𝐺 is a perfect graph if and only if S𝐻𝐺 is a perfect 𝑛-SuperHyperGraph. Proof. (1) By construction, S𝐻 has no super-links at levels ≥ 2. Hence for every 𝑈 ⊆ 𝑉 we have 𝐺 0 (S𝐻 [𝑈]) = 𝜕 𝐻 [𝑈] , and for each 1 ≤ 𝑖 ≤ 𝑛 − 1 the level graph 𝐺 𝑖 (S𝐻 [𝑈]) has vertex set E𝑖 [𝑈] = ∅, hence is an empty graph and satisfies 𝜒 = 𝜔 = 0. Therefore, the definition of perfect 𝑛-SuperHyperGraph for S𝐻 reduces to ∀𝑈 ⊆ 𝑉 : 𝜒 𝜕 (𝐻 [𝑈]) = 𝜔 𝜕 (𝐻 [𝑈]) , which is exactly the definition of a perfect hypergraph (shadow-perfect). Thus 𝐻 is perfect if and only if S𝐻 is perfect. (2) For the 2-uniform hypergraph 𝐻𝐺 , its shadow graph satisfies 𝜕 (𝐻𝐺 ) = 𝐺, because a pair {𝑢, 𝑣} is an edge of 𝜕 (𝐻𝐺 ) exactly when {𝑢, 𝑣} is contained in some hyperedge of 𝐻𝐺 , and the hyperedges of 𝐻𝐺 are precisely the edges of 𝐺. More generally, for every 𝑈 ⊆ 𝑉, 𝜕 𝐻𝐺 [𝑈] = 𝐺 [𝑈]. Applying (1) to 𝐻𝐺 yields that S𝐻𝐺 is perfect if and only if ∀𝑈 ⊆ 𝑉 : 𝜒 𝐺 [𝑈] = 𝜔 𝐺 [𝑈] , which is exactly the definition that 𝐺 is perfect. □ 88

90.

Chapter 4. Some Particular SuperHyperGraphs 4.15 Line SuperHyperGraphs Line graph represents each edge of an original graph as a vertex, connecting vertices whenever corresponding edges share an endpoint [442–444]. Related notions include the fuzzy line graph [443, 445], the neutrosophic line graph [446, 447], the weighted line graph [448, 449], and the plithogenic line graph [444]. Also, active research has been conducted on related topics such as total graphs [450,451], line digraphs [452,453], pancyclic line graphs [454], quasi-line graphs [455, 456], and iterated line graphs [457, 458]. Line hypergraph uses each hyperedge as a vertex, adding hyperedges that connect hyperedges sharing at least one common original vertex [459, 460]. Line SuperHypergraph takes each n-superedge as vertex, forming superedges from stars: sets of superedges incident to same n-supervertex within structure [461]. Definition 4.15.1 (Line hypergraph). [459,460] Let 𝐻 = (𝑉, 𝐸) be a finite hypergraph. For each 𝑣 ∈ 𝑉, define the star Star 𝐻 (𝑣) := { 𝑒 ∈ 𝐸 | 𝑣 ∈ 𝑒 } ⊆ 𝐸 . The line hypergraph of 𝐻 is the hypergraph 𝐿 (𝐻) := 𝐸, { Star 𝐻 (𝑣) | 𝑣 ∈ 𝑉, Star 𝐻 (𝑣) ≠ ∅ } . Thus, vertices of 𝐿(𝐻) are the hyperedges of 𝐻, and each 𝑣 ∈ 𝑉 contributes a hyperedge of 𝐿(𝐻) collecting all hyperedges of 𝐻 incident with 𝑣. Definition 4.15.2 (Multi-valued line hypergraph (Tyshkevich–Zverovich)). Let 𝐻 = (𝑉, 𝐸) be a hypergraph without isolated vertices, and list 𝑉 = {𝑣 1 , . . . , 𝑣 𝑛 }. Let deg(𝑣) denote the number of hyperedges containing 𝑣. Define integer vectors 1 𝐻 := deg(𝑣 1 ), . . . , deg(𝑣 𝑛 ) , 0 𝐻 := 0𝑣1 , . . . , 0𝑣𝑛 , where ( 0𝑣𝑖 := 0, 2, deg(𝑣 𝑖 ) = 1, deg(𝑣 𝑖 ) ≥ 2. Let 𝑛 𝐷 𝐻 := { 𝐷 = (𝑑 𝑣𝑖 )𝑖=1 | 0 𝐻 ≤ 𝐷 ≤ 1 𝐻 componentwise }. For 𝑣 ∈ 𝑉, write 𝐸 (𝑣) := Star 𝐻 (𝑣) = {𝑒 ∈ 𝐸 | 𝑣 ∈ 𝑒}. For 𝐷 ∈ 𝐷 𝐻 and 𝑣 ∈ 𝑉, let 𝐹𝑣 be the clique of rank 𝑑 𝑣 on the vertex set 𝐸 (𝑣), i.e., 𝐹𝑣 := 𝐸 (𝑣), { 𝑆 ⊆ 𝐸 (𝑣) | |𝑆| = 𝑑 𝑣 } . Define 𝐿 𝐷 (𝐻) := Ø 𝐹𝑣 . 𝑣 ∈𝑉 The (multi-valued) line hypergraph of 𝐻 is the set L (𝐻) := { 𝐿 𝐷 (𝐻) | 𝐷 ∈ 𝐷 𝐻 }. Definition 4.15.3 ((Recall) Iterated powerset and level-𝑛 SuperHyperGraph). Let 𝑉0 be a nonempty finite base set. Define the iterated powersets P0 (𝑉0 ) := 𝑉0 , P 𝑘+1 (𝑉0 ) := P P 𝑘 (𝑉0 ) (𝑘 ≥ 0), where P(𝑋) denotes the usual powerset of a set 𝑋. Fix 𝑛 ∈ N0 . A level-𝑛 SuperHyperGraph is a pair 𝐻 (𝑛) = (𝑉𝑛 , 𝐸), where 𝑉𝑛 ⊆ P𝑛 (𝑉0 ) is a finite set of 𝑛-supervertices, and ∅ ≠ 𝐸 ⊆ P(𝑉𝑛 ) \ {∅} is a finite family of nonempty subsets of 𝑉𝑛 , whose elements are called 𝑛-superedges. For 𝑣 ∈ 𝑉𝑛 , the star of 𝑣 in 𝐻 (𝑛) is Star 𝐻 (𝑛) (𝑣) := { 𝐹 ∈ 𝐸 : 𝑣 ∈ 𝐹 } ⊆ 𝐸 . 89

#p281
#p282

91.

[beta]

Chapter 4. Some Particular SuperHyperGraphs
Definition 4.15.4 (Line SuperHyperGraph). [461] Let 𝐻 (𝑛) = (𝑉𝑛 , 𝐸) be a level-𝑛 SuperHyperGraph on the
finite base set 𝑉0 . The line SuperHyperGraph of 𝐻 (𝑛) is the pair

′
′ 
𝐿 (𝑛) 𝐻 (𝑛) := 𝑉𝑛+1
, 𝐸 𝑛+1
,
defined as follows:
• the vertex set is the set of superedges of 𝐻 (𝑛) ,
′
𝑉𝑛+1
:= 𝐸;

• the superedge family is the collection of all nonempty stars,

′
𝐸 𝑛+1
:= Star 𝐻 (𝑛) (𝑣) ⊆ 𝐸 𝑣 ∈ 𝑉𝑛 , Star 𝐻 (𝑛) (𝑣) ≠ ∅ .
Since 𝑉𝑛 ⊆ P𝑛 (𝑉0 ), we have

′
𝑉𝑛+1
= 𝐸 ⊆ P(𝑉𝑛 ) ⊆ P P𝑛 (𝑉0 ) = P𝑛+1 (𝑉0 ),

′
′ . Hence 𝐿 (𝑛) 𝐻 (𝑛) is a level-(𝑛 + 1) SuperHyperGraph.
and each element of 𝐸 𝑛+1
is a nonempty subset of 𝑉𝑛+1

Intuitively, 𝐿 (𝑛) 𝐻 (𝑛) has one vertex for each 𝑛-superedge of 𝐻 (𝑛) , and for every 𝑛-supervertex 𝑣 ∈ 𝑉𝑛 it adds
a (super)hyperedge collecting all superedges that contain 𝑣.
Example 4.15.5 (A simple line SuperHyperGraph). Let 𝑉0 := {1, 2, 3} and take 𝑛 = 0. Then P0 (𝑉0 ) = 𝑉0 , and
we consider the level-0 SuperHyperGraph
𝐻 (0) = (𝑉0 , 𝐸),
where


𝐸 = 𝑒 1 , 𝑒 2 = {1, 2}, {2, 3} .

𝑉0 = {1, 2, 3},

Thus 𝑒 1 = {1, 2} and 𝑒 2 = {2, 3} are the 0-superedges.
For each vertex 𝑣 ∈ 𝑉0 the star in 𝐻 (0) is
Star 𝐻 (0) (1) = {𝑒 1 },

Star 𝐻 (0) (2) = {𝑒 1 , 𝑒 2 },

Star 𝐻 (0) (3) = {𝑒 2 }.

The line SuperHyperGraph of 𝐻 (0) is


𝐿 (0) 𝐻 (0) = 𝑉1′ , 𝐸 1′ ,
where the vertex set is the set of superedges of 𝐻 (0) ,
𝑉1′ := 𝐸 = {𝑒 1 , 𝑒 2 },
and the superedge family is the collection of all nonempty stars,

𝐸 1′ := {𝑒 1 }, {𝑒 1 , 𝑒 2 }, {𝑒 2 } .

Since 𝑉1′ ⊆ P1 (𝑉0 ) = P(𝑉0 ) and each element of 𝐸 1′ is a nonempty subset of 𝑉1′ , this shows that 𝐿 (0) 𝐻 (0) is a
level-1 SuperHyperGraph obtained as the line SuperHyperGraph of 𝐻 (0) .
Definition 4.15.6 (Multi-valued line SuperHyperGraph). Let 𝑉0 be a finite nonempty base set, let 𝑛 ∈ N0 , and
let
𝐻 (𝑛) = (𝑉𝑛 , 𝐸)
be a level-𝑛 SuperHyperGraph on 𝑉0 , where 𝑉𝑛 ⊆ P𝑛 (𝑉0 ) is the finite set of 𝑛-supervertices and 𝐸 ⊆ P(𝑉𝑛 ) \{∅}
is the finite family of nonempty 𝑛-superedges.
For each 𝑣 ∈ 𝑉𝑛 , define its star and degree by
𝐸 (𝑣) := Star 𝐻 (𝑛) (𝑣) := { 𝐹 ∈ 𝐸 | 𝑣 ∈ 𝐹 } ⊆ 𝐸,
90

deg(𝑣) := |𝐸 (𝑣)|.

#p282

92.

Chapter 4. Some Particular SuperHyperGraphs Assume that 𝐻 (𝑛) has no isolated 𝑛-supervertices, i.e. deg(𝑣) ≥ 1 for all 𝑣 ∈ 𝑉𝑛 . Fix an enumeration 𝑉𝑛 = {𝑣 1 , . . . , 𝑣 𝑚 } and define integer vectors 1 𝐻 (𝑛) := deg(𝑣 1 ), . . . , deg(𝑣 𝑚 ) , 0 𝐻 (𝑛) := 0𝑣1 , . . . , 0𝑣𝑚 , where ( 0𝑣𝑖 := Let n 𝑚 𝐷 𝐻 (𝑛) := 𝐷 = (𝑑 𝑣𝑖 )𝑖=1 deg(𝑣 𝑖 ) = 1, deg(𝑣 𝑖 ) ≥ 2. 0, 2, o 0 𝐻 (𝑛) ≤ 𝐷 ≤ 1 𝐻 (𝑛) componentwise . For a finite set 𝑋 and an integer 𝑟 ≥ 0, define the rank-𝑟 clique hypergraph on 𝑋 by     𝑋, { 𝑆 ⊆ 𝑋 | |𝑆| = 𝑟 } , 𝑟 ≥ 1, Clique𝑟 (𝑋) :=   𝑋, ∅ , 𝑟 = 0.  For 𝐷 ∈ 𝐷 𝐻 (𝑛) and 𝑣 ∈ 𝑉𝑛 , set 𝐹𝑣,𝐷 := Clique𝑑𝑣 𝐸 (𝑣) , and define the 𝐷-line SuperHyperGraph of 𝐻 (𝑛) as (𝑛) 𝐿𝐷 𝐻 (𝑛) := 𝐸, 𝐸 𝐷 , Ø 𝐸 𝐷 := 𝐸 𝐹𝑣,𝐷 . 𝑣 ∈𝑉𝑛 Finally, the multi-valued line SuperHyperGraph of 𝐻 (𝑛) is the family o n (𝑛) 𝐻 (𝑛) 𝐷 ∈ 𝐷 𝐻 (𝑛) . L (𝑛) 𝐻 (𝑛) := 𝐿 𝐷 Example 4.15.7 (A concrete multi-valued line SuperHyperGraph). Let the finite base set be 𝑉0 := {𝑎, 𝑏}, and take 𝑛 = 1, so P1 (𝑉0 ) = P(𝑉0 ) = {∅, {𝑎}, {𝑏}, {𝑎, 𝑏}}. Choose the following 1-supervertices (nonempty subsets of 𝑉0 ): 𝑣 1 := {𝑎}, 𝑣 2 := {𝑏}, 𝑣 3 := {𝑎, 𝑏}. Thus 𝑉1 := {𝑣 1 , 𝑣 2 , 𝑣 3 } ⊆ P1 (𝑉0 ). Define a level-1 SuperHyperGraph 𝐻 (1) = (𝑉1 , 𝐸) with three nonempty 1-superedges 𝑒 1 := {𝑣 1 , 𝑣 3 }, 𝑒 2 := {𝑣 2 , 𝑣 3 }, 𝑒 3 := {𝑣 1 , 𝑣 2 }, and hence 𝐸 := {𝑒 1 , 𝑒 2 , 𝑒 3 } ⊆ P(𝑉1 ) \ {∅}. Every supervertex has positive degree, so 𝐻 (1) has no isolated 1-supervertices. Step 1: stars and degrees. Compute the stars: 𝐸 (𝑣 1 ) = {𝑒 1 , 𝑒 3 }, 𝐸 (𝑣 2 ) = {𝑒 2 , 𝑒 3 }, 𝐸 (𝑣 3 ) = {𝑒 1 , 𝑒 2 }, so deg(𝑣 1 ) = deg(𝑣 2 ) = deg(𝑣 3 ) = 2. Step 2: admissible vectors 𝐷. Enumerate 𝑉1 = {𝑣 1 , 𝑣 2 , 𝑣 3 }. Then 1 𝐻 (1) = (2, 2, 2), 0 𝐻 (1) = (2, 2, 2) 91

93.

Chapter 4. Some Particular SuperHyperGraphs because each degree is ≥ 2 and hence each 0𝑣𝑖 = 2. Therefore the admissible set is a singleton: 𝐷 𝐻 (1) = {(2, 2, 2)}. Let 𝐷 = (2, 2, 2). Step 3: build the 𝐷-line SuperHyperGraph. For each 𝑣 𝑖 , since 𝑑 𝑣𝑖 = 2 and |𝐸 (𝑣 𝑖 )| = 2, the rank-2 clique hypergraph Clique2 (𝐸 (𝑣 𝑖 )) contributes exactly one hyperedge, namely 𝐸 (𝑣 𝑖 ) itself: 𝐸 𝐹𝑣1 ,𝐷 = {𝑒 1 , 𝑒 3 } , 𝐸 𝐹𝑣2 ,𝐷 = {𝑒 2 , 𝑒 3 } , 𝐸 𝐹𝑣3 ,𝐷 = {𝑒 1 , 𝑒 2 } . Hence 𝐸𝐷 = Ø o n 𝐸 𝐹𝑣,𝐷 = {𝑒 1 , 𝑒 3 }, {𝑒 2 , 𝑒 3 }, {𝑒 1 , 𝑒 2 } . 𝑣 ∈𝑉1 Thus the (unique) 𝐷-line SuperHyperGraph is (1) 𝐿𝐷 𝐻 (1) = 𝐸, 𝐸 𝐷 , where the vertex set is 𝐸 = {𝑒 1 , 𝑒 2 , 𝑒 3 } and the hyperedge family is 𝐸 𝐷 = {{𝑒 1 , 𝑒 3 }, {𝑒 2 , 𝑒 3 }, {𝑒 1 , 𝑒 2 }}. Step 4: the multi-valued line SuperHyperGraph. Since 𝐷 𝐻 (1) = {𝐷}, the multi-valued line SuperHyperGraph is the singleton family n (1) (1) o 𝐻 . L (1) 𝐻 (1) = 𝐿 𝐷 (1) Vertices of 𝐿 𝐷 (𝐻 (1) ) correspond to the original 1-superedges 𝑒 1 , 𝑒 2 , 𝑒 3 . Each original supervertex 𝑣 𝑖 produces a hyperedge on {𝑒 ∈ 𝐸 | 𝑣 𝑖 ∈ 𝑒}, i.e. on its star. (𝑛) 𝐻 (𝑛) = 𝐸, 𝐸 𝐷 is a level-(𝑛 + 1) SuperHyperGraph Lemma 4.15.8. For every 𝐷 ∈ 𝐷 𝐻 (𝑛) , the object 𝐿 𝐷 on the same base set 𝑉0 . Proof. Since 𝐸 ⊆ P(𝑉𝑛 ) and 𝑉𝑛 ⊆ P𝑛 (𝑉0 ), we have 𝐸 ⊆ P(𝑉𝑛 ) ⊆ P P𝑛 (𝑉0 ) = P𝑛+1 (𝑉0 ), (𝑛) so the vertex set 𝐸 of 𝐿 𝐷 (𝐻 (𝑛) ) is a finite subset of P𝑛+1 (𝑉0 ). Moreover, each hyperedge in 𝐸 𝐷 is a subset of 𝐸 (because 𝐸 (𝐹𝑣,𝐷 ) ⊆ P(𝐸 (𝑣)) ⊆ P(𝐸)), and by construction every hyperedge in 𝐸 (𝐹𝑣,𝐷 ) has cardinality 𝑑 𝑣 when 𝑑 𝑣 ≥ 1, hence is nonempty. Therefore 𝐸 𝐷 ⊆ P(𝐸) \ {∅} is a finite family of nonempty subsets of 𝐸. This is exactly the definition of a level-(𝑛 + 1) SuperHyperGraph. □ Theorem 4.15.9 (Generalization properties). Let 𝐻 (𝑛) = (𝑉𝑛 , 𝐸) be a level-𝑛 SuperHyperGraph without isolated 𝑛-supervertices, and let L (𝑛) (𝐻 (𝑛) ) be its multi-valued line SuperHyperGraph as in Definition 4.15.6. (i) (Generalizes the multi-valued line hypergraph.) If 𝑛 = 0, then 𝐻 (0) = (𝑉0 , 𝐸) is an ordinary hypergraph (with no isolated vertices), and the family L (0) (𝐻 (0) ) coincides with the Tyshkevich–Zverovich multivalued line hypergraph construction L (𝐻). (ii) (Generalizes the line SuperHyperGraph.) Let 𝐷 max ∈ 𝐷 𝐻 (𝑛) be defined by 𝑑 𝑣max = deg(𝑣) for every 𝑣 ∈ 𝑉𝑛 (i.e. 𝐷 max = 1 𝐻 (𝑛) ). Then (𝑛) (𝑛) 𝐿𝐷 max 𝐻 = 𝐿 (𝑛) 𝐻 (𝑛) , where 𝐿 (𝑛) (𝐻 (𝑛) ) is the (single-valued) line SuperHyperGraph defined via stars. 92

#p91

94.

[beta]

Chapter 4. Some Particular SuperHyperGraphs
Proof. (i) Assume 𝑛 = 0. Then P0 (𝑉0 ) = 𝑉0 and 𝑉0 is precisely the vertex set of the hypergraph 𝐻 (0) = (𝑉0 , 𝐸).
For each 𝑣 ∈ 𝑉0 , the star
𝐸 (𝑣) = { ℎ ∈ 𝐸 | 𝑣 ∈ ℎ }
is exactly the usual star used in the definition of the (multi-valued) line hypergraph. The degree deg(𝑣) = |𝐸 (𝑣)|
also matches the usual hypergraph degree. Hence the vectors 0 𝐻 (0) , 1 𝐻 (0) and the admissible set 𝐷 𝐻 (0) agree
with those in the Tyshkevich–Zverovich construction. For each 𝐷 ∈ 𝐷 𝐻 (0) , the hyperedges contributed by 𝑣
are precisely the 𝑑 𝑣 -subsets of 𝐸 (𝑣) when 𝑑 𝑣 ≥ 1 (and none when 𝑑 𝑣 = 0), i.e. the rank-𝑑 𝑣 clique on 𝐸 (𝑣).
Therefore the resulting hypergraph on vertex set 𝐸 is exactly 𝐿 𝐷 (𝐻), and so
(0)
L (0) (𝐻 (0) ) = { 𝐿 𝐷
(𝐻 (0) ) | 𝐷 ∈ 𝐷 𝐻 (0) } = { 𝐿 𝐷 (𝐻) | 𝐷 ∈ 𝐷 𝐻 } = L (𝐻).

(ii) Fix 𝑛 ≥ 0 and let 𝐷 max = 1 𝐻 (𝑛) , so that 𝑑 𝑣max = deg(𝑣) = |𝐸 (𝑣)|. For any 𝑣 ∈ 𝑉𝑛 , the rank-deg(𝑣) clique
on 𝐸 (𝑣) has exactly one hyperedge, namely 𝐸 (𝑣) itself: indeed,
{ 𝑆 ⊆ 𝐸 (𝑣) | |𝑆| = deg(𝑣) } = { 𝐸 (𝑣) }.
Thus

𝐸 𝐹𝑣,𝐷 max = { 𝐸 (𝑣) } = { Star 𝐻 (𝑛) (𝑣) }.
Taking the union over all 𝑣 ∈ 𝑉𝑛 , we obtain
Ø
Ø

𝐸 𝐷 max =
𝐸 𝐹𝑣,𝐷 max =
{ Star 𝐻 (𝑛) (𝑣) } = { Star 𝐻 (𝑛) (𝑣) | 𝑣 ∈ 𝑉𝑛 },
𝑣 ∈𝑉𝑛

𝑣 ∈𝑉𝑛

where duplicates (if any) are ignored because we are working with a set of hyperedges. Therefore


(𝑛)
(𝑛) 
𝐿𝐷
= 𝐸, { Star 𝐻 (𝑛) (𝑣) | 𝑣 ∈ 𝑉𝑛 } = 𝐿 (𝑛) 𝐻 (𝑛) ,
max 𝐻
which is exactly the star-based line SuperHyperGraph.

4.16

□

Total Superhypergraph

Total graph of 𝐺 has vertices 𝑉 (𝐺) ∪ 𝐸 (𝐺); adjacency means adjacent vertices, adjacent edges, or incidence
between vertex and edge [450, 462, 463]. Total hypergraph 𝑇 (𝐻) uses 𝑉 ⊎ 𝐸 as vertices; hyperedges encode
original edges, vertex-stars, and vertex–incident edge sets [461]. Total 𝑛-superhypergraph of 𝐻 (𝑛) uses
𝜄(𝑉𝑛 ) ⊎ 𝐸 𝑛 ; superedges encode incidences, stars, and lifted original superedges together [461].
Definition 4.16.1 (Total HyperGraph). [461] Let 𝐻 = (𝑉, 𝐸) be a finite hypergraph, i.e., 𝑉 ≠ ∅ and
𝐸 ⊆ P (𝑉) \ {∅}. Define the (typed) disjoint union
𝑈 := 𝑉 ⊎ 𝐸,
with canonical injections 𝜄𝑉 : 𝑉 → 𝑈 and 𝜄𝐸 : 𝐸 → 𝑈. For each 𝑣 ∈ 𝑉, define the star (incidence family)
Star 𝐻 (𝑣) := { 𝑒 ∈ 𝐸 : 𝑣 ∈ 𝑒 } ⊆ 𝐸 .
Define three families of hyperedges on 𝑈 by

𝐴 := {𝜄𝑉 (𝑥) : 𝑥 ∈ 𝑒} : 𝑒 ∈ 𝐸 ,


{𝜄𝐸 ( 𝑓 ) : 𝑓 ∈ Star 𝐻 (𝑣)} : 𝑣 ∈ 𝑉, | Star 𝐻 (𝑣)| ≥ 2 ,

𝐶 := {𝜄𝑉 (𝑣)} ∪ {𝜄𝐸 ( 𝑓 ) : 𝑓 ∈ Star 𝐻 (𝑣)} : 𝑣 ∈ 𝑉 .

𝐵 :=

The total hypergraph of 𝐻 is the hypergraph
𝑇 (𝐻) := (𝑈, 𝐴 ∪ 𝐵 ∪ 𝐶).

A concrete example is given below.
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Chapter 4. Some Particular SuperHyperGraphs Example 4.16.2 (A concrete total hypergraph). Let 𝑉 = {1, 2, 3}, 𝐸 = {𝑒 1 , 𝑒 2 }, 𝑒 1 = {1, 2}, 𝑒 2 = {2, 3}. Then 𝐻 = (𝑉, 𝐸) is a finite hypergraph. The stars are Star 𝐻 (1) = {𝑒 1 }, Star 𝐻 (2) = {𝑒 1 , 𝑒 2 }, Star 𝐻 (3) = {𝑒 2 }. Form the typed disjoint union 𝑈 := 𝑉 ⊎ 𝐸 = {1, 2, 3, 𝑒 1 , 𝑒 2 }, where elements from 𝑉 and 𝐸 are regarded as different types. The three hyperedge families in Definition 4.16.1 are: 𝐴 = {𝜄𝑉 (1), 𝜄𝑉 (2)}, {𝜄𝑉 (2), 𝜄𝑉 (3)} , 𝐵 = {𝜄𝐸 (𝑒 1 ), 𝜄𝐸 (𝑒 2 )} (only 𝑣 = 2 has | Star 𝐻 (𝑣)| ≥ 2), 𝐶 = {𝜄𝑉 (1), 𝜄𝐸 (𝑒 1 )}, {𝜄𝑉 (2), 𝜄𝐸 (𝑒 1 ), 𝜄𝐸 (𝑒 2 )}, {𝜄𝑉 (3), 𝜄𝐸 (𝑒 2 )} . Hence the total hypergraph is 𝑇 (𝐻) = (𝑈, 𝐴 ∪ 𝐵 ∪ 𝐶). Definition 4.16.3 (Total 𝑛-SuperHyperGraph (Total SuperHyperGraph)). [461] Fix a finite base set 𝑉0 and 𝑛 ∈ N0 . Let 𝐻 (𝑛) = (𝑉𝑛 , 𝐸 𝑛 ) be a level-𝑛 SuperHyperGraph over 𝑉0 , meaning that 𝑉𝑛 ⊆ P 𝑛 (𝑉0 ) is finite and 𝐸 𝑛 ⊆ P (𝑉𝑛 ) \ {∅} is finite. Set 𝑈𝑛+1 := 𝜄(𝑉𝑛 ) ⊎ 𝐸 𝑛 , where 𝜄 : 𝑉𝑛 → P (𝑉𝑛 ) is the singleton embedding 𝜄(𝑣) = {𝑣}, and ⊎ indicates a typed disjoint union. For each 𝑣 ∈ 𝑉𝑛 , define the star Star 𝐻 (𝑛) (𝑣) := { 𝐸 ∈ 𝐸 𝑛 : 𝑣 ∈ 𝐸 } ⊆ 𝐸 𝑛 . Define three families of (super)hyperedges on 𝑈𝑛+1 by 𝐴 := {𝜄(𝑢) : 𝑢 ∈ 𝐸 } : 𝐸 ∈ 𝐸 𝑛 , Star 𝐻 (𝑛) (𝑣) : 𝑣 ∈ 𝑉𝑛 , | Star 𝐻 (𝑛) (𝑣)| ≥ 2 , 𝐶 := {𝜄(𝑣)} ∪ Star 𝐻 (𝑛) (𝑣) : 𝑣 ∈ 𝑉𝑛 . 𝐵 := The total 𝑛-superhypergraph (or total superhypergraph) of 𝐻 (𝑛) is 𝑇 𝐻 (𝑛) := 𝑈𝑛+1 , 𝐴 ∪ 𝐵 ∪ 𝐶 . A concrete example is given below. Example 4.16.4 (A concrete total 𝑛-superhypergraph (take 𝑛 = 1)). Let the base set be 𝑉0 = {𝑎, 𝑏, 𝑐}, and take 𝑛 = 1, so P 1 (𝑉0 ) = P (𝑉0 ). Define the level-1 superhypergraph 𝐻 (1) = (𝑉1 , 𝐸 1 ) by 𝑉1 = {𝑎}, {𝑏}, {𝑐} ⊆ P (𝑉0 ), 𝐸 1 = {𝐸 ∗ , 𝐸 † }, 𝐸 ∗ = {𝑎}, {𝑏} , 𝐸 † = {𝑏}, {𝑐} . For each 𝑣 ∈ 𝑉1 , its star is Star 𝐻 (1) ({𝑎}) = {𝐸 ∗ }, Star 𝐻 (1) ({𝑏}) = {𝐸 ∗ , 𝐸 † }, 94 Star 𝐻 (1) ({𝑐}) = {𝐸 † }.

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The singleton embedding is 𝜄(𝑣) = {𝑣}, so

𝜄(𝑉1 ) = {{𝑎}}, {{𝑏}}, {{𝑐}} .
Define the typed disjoint union

𝑈2 := 𝜄(𝑉1 ) ⊎ 𝐸 1 = {{𝑎}}, {{𝑏}}, {{𝑐}}, 𝐸 ∗ , 𝐸 † .
Now compute the three families in Definition 4.16.3:


𝐴 = {𝜄({𝑎}), 𝜄({𝑏})}, {𝜄({𝑏}), 𝜄({𝑐})} = {{{𝑎}}, {{𝑏}}}, {{{𝑏}}, {{𝑐}}} ,


𝐵 = Star 𝐻 (1) ({𝑏}) = {𝐸 ∗ , 𝐸 † } ,

𝐶 = {𝜄({𝑎})} ∪ Star 𝐻 (1) ({𝑎}), {𝜄({𝑏})} ∪ Star 𝐻 (1) ({𝑏}), {𝜄({𝑐})} ∪ Star 𝐻 (1) ({𝑐})

= {{{𝑎}}, 𝐸 ∗ }, {{{𝑏}}, 𝐸 ∗ , 𝐸 † }, {{{𝑐}}, 𝐸 † } .
Therefore the total 1-superhypergraph is


𝑇 𝐻 (1) = (𝑈2 , 𝐴 ∪ 𝐵 ∪ 𝐶).

4.17

Interval SuperHypergraphs

An interval graph represents each vertex as a real line interval, adding edges whenever the corresponding
intervals intersect in order [464, 465]. Related concepts include proper interval graphs [466, 467], interval
bigraphs [468, 469], co-interval graphs [470, 471], and fuzzy interval graphs [472, 473], among others. An
interval hypergraph assigns each hyperedge to a contiguous block of ordered vertices, so every hyperedge
equals one underlying interval [474, 475]. An interval SuperHypergraph organizes level supervertices over an
ordered base set, requiring each superedge’s flattened support to form one interval.
Definition 4.17.1 (Interval hypergraph). (cf. [17, 474, 475]) Let 𝑉 be a nonempty finite set equipped with a
total order ≤. For 𝑥, 𝑦 ∈ 𝑉 with 𝑥 ≤ 𝑦, define the (closed) interval
[𝑥, 𝑦] ≤ := { 𝑧 ∈ 𝑉 | 𝑥 ≤ 𝑧 ≤ 𝑦 }.
A hypergraph 𝐻 = (𝑉, 𝐸) (without loops) is called an interval hypergraph if there exists a total order ≤ on 𝑉
such that for every hyperedge 𝑒 ∈ 𝐸 there are vertices 𝑥, 𝑦 ∈ 𝑉 with 𝑥 ≤ 𝑦 and
𝑒 = [𝑥, 𝑦] ≤ .
A concrete example is given below.
Example 4.17.2 (Interval hypergraph). Let
𝑉 := {1, 2, 3, 4}
equipped with the natural total order
1 < 2 < 3 < 4.
For 𝑥, 𝑦 ∈ 𝑉 with 𝑥 ≤ 𝑦, the interval is
[𝑥, 𝑦] ≤ := { 𝑧 ∈ 𝑉 | 𝑥 ≤ 𝑧 ≤ 𝑦 }.
Define the hyperedges
𝑒 1 := [1, 3] ≤ = {1, 2, 3},

𝑒 2 := [2, 4] ≤ = {2, 3, 4},

and let
𝐸 := {𝑒 1 , 𝑒 2 }.
Then
𝐻 := (𝑉, 𝐸)
is a hypergraph in which every hyperedge is exactly an interval of (𝑉, ≤). Hence 𝐻 is an interval hypergraph.
95

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Chapter 4. Some Particular SuperHyperGraphs
Definition 4.17.3 ((Recall) Iterated powerset and flattening). Let 𝑉0 be a finite base set. For each integer 𝑘 ≥ 0
define the iterated powerset by

𝑃0 (𝑉0 ) := 𝑉0 ,
𝑃 𝑘+1 (𝑉0 ) := 𝑃 𝑃 𝑘 (𝑉0 ) ,
where 𝑃(·) denotes the usual powerset.
Assume 𝑉0 is equipped with a total order ≤. For each 𝑘 ≥ 0 define the flattening map
flat 𝑘 : 𝑃 𝑘 (𝑉0 ) −→ 𝑃(𝑉0 )
recursively by
flat0 (𝑥) := {𝑥}
and, for 𝑘 ≥ 0,
flat 𝑘+1 (𝑋) :=

Ø

(𝑥 ∈ 𝑉0 ),


for 𝑋 ∈ 𝑃 𝑘+1 (𝑉0 ) = 𝑃 𝑃 𝑘 (𝑉0 ) .

flat 𝑘 (𝑌 )

𝑌 ∈𝑋

Definition 4.17.4 (Interval 𝑛-SuperHyperGraph). Let 𝑉0 be a finite set with a total order ≤, and let 𝐻 (𝑛) = (𝑉, 𝐸)
be an 𝑛-SuperHyperGraph with 𝑉 ⊆ 𝑃𝑛 (𝑉0 ) and 𝐸 ⊆ 𝑃∗ (𝑉).
For 𝑥, 𝑦 ∈ 𝑉0 with 𝑥 ≤ 𝑦, write
[𝑥, 𝑦] ≤ := { 𝑧 ∈ 𝑉0 | 𝑥 ≤ 𝑧 ≤ 𝑦 }.
We say that 𝐻 (𝑛) is an interval 𝑛-SuperHyperGraph if there exists a total order ≤ on 𝑉0 such that for every
superedge 𝑒 ∈ 𝐸 there are vertices 𝑥, 𝑦 ∈ 𝑉0 with 𝑥 ≤ 𝑦 and
supp(𝑒) = [𝑥, 𝑦] ≤ .
A concrete example is given below.
Example 4.17.5 (Interval 2-SuperHyperGraph). Let
𝑉0 := {1, 2, 3, 4}
equipped with the natural order 1 < 2 < 3 < 4. Recall that
P0 (𝑉0 ) = 𝑉0 ,

P1 (𝑉0 ) = P(𝑉0 ),

Consider the following 2-supervertices:

𝑣 1 := {1, 2}, {2, 3} ,


P2 (𝑉0 ) = P P(𝑉0 ) .


𝑣 2 := {2, 3}, {3, 4} ,

so that 𝑣 1 , 𝑣 2 ∈ P2 (𝑉0 ). Put
𝑉 := {𝑣 1 , 𝑣 2 } ⊆ P2 (𝑉0 ),
and define a single 2-superedge
𝑒 := {𝑣 1 , 𝑣 2 },

𝐸 := {𝑒} ⊆ P∗ (𝑉).

Then
𝐻 (2) := (𝑉, 𝐸)
is a 2-SuperHyperGraph.
Let flat2 : P2 (𝑉0 ) → P(𝑉0 ) be the flattening map (from the recalled definition), so that for a 2-element
𝑌 ∈ P2 (𝑉0 ),
Ø
flat2 (𝑌 ) =
𝑋.
𝑋∈𝑌

By definition of the support of a superedge,
Ø 

supp(𝑒) = flat2
𝑣 = flat2 𝑣 1 ∪ 𝑣 2 .
𝑣 ∈𝑒

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Since
𝑣 1 ∪ 𝑣 2 = {{1, 2}, {2, 3}, {3, 4}},
we obtain
supp(𝑒) = {1, 2} ∪ {2, 3} ∪ {3, 4} = {1, 2, 3, 4} = [1, 4] ≤ .
Thus supp(𝑒) is exactly an interval of (𝑉0 , ≤), so 𝐻 (2) is an interval 2-SuperHyperGraph (with respect to the
total order 1 < 2 < 3 < 4).
The overview of the comparison of interval graphs, interval hypergraphs, and interval n-SuperHyperGraphs is
presented in Table 4.9.
Table 4.9: Comparison of interval graphs, interval hypergraphs, and interval 𝑛-SuperHyperGraphs
Framework

Underlying objects

Interval condition

Interval graph

Simple graph 𝐺 = (𝑉, 𝐸); each vertex
𝑣 ∈ 𝑉 is represented by an interval 𝐼 𝑣
on the real line.
Hypergraph 𝐻 = (𝑉, 𝐸) with a total
order ≤ on 𝑉; hyperedges 𝑒 ∈ 𝐸 ⊆
P∗ (𝑉).
𝑛-SuperHyperGraph 𝐻 (𝑛) = (𝑉, 𝐸)
with 𝑉 ⊆ 𝑃𝑛 (𝑉0 ) over an ordered base
set (𝑉0 , ≤).

There is an edge 𝑢𝑣 ∈ 𝐸 if and only
if 𝐼𝑢 ∩ 𝐼 𝑣 ≠ ∅, i.e. edges arise exactly
from intersecting intervals.
For each 𝑒 ∈ 𝐸 there exist 𝑥, 𝑦 ∈ 𝑉
with 𝑥 ≤ 𝑦 such that 𝑒 = [𝑥, 𝑦] ≤ =
{𝑧 ∈ 𝑉 | 𝑥 ≤ 𝑧 ≤ 𝑦}.
For each superedge 𝑒 ∈ 𝐸 there exist
𝑥, 𝑦 ∈ 𝑉0 with 𝑥 ≤ 𝑦 such that the
flattened support supp(𝑒) equals the
interval [𝑥, 𝑦] ≤ .

Interval hypergraph

Interval
SuperHyperGraph

𝑛-

Theorem 4.17.6 (Interval 𝑛-SuperHyperGraphs generalize interval hypergraphs). Let 𝑉0 be a finite set with a
total order ≤. Consider the following two structures on 𝑉0 :
1. A hypergraph 𝐻 = (𝑉0 , 𝐸).
2. A 0-SuperHyperGraph
𝐻 (0) = (𝑉, 𝐸)

with 𝑉 := 𝑉0 , 𝐸 := 𝐸 .

Then 𝐻 is an interval hypergraph (in the sense of the above definition) if and only if 𝐻 (0) is an interval
0-SuperHyperGraph. Hence, interval 𝑛-SuperHyperGraphs (for general 𝑛) extend the notion of interval
hypergraphs, which are exactly the case 𝑛 = 0.
Proof. First note that for 𝑛 = 0 we have 𝑃0 (𝑉0 ) = 𝑉0 and, by definition of the flattening map,
flat0 (𝑥) = {𝑥}

for all 𝑥 ∈ 𝑉0 .

Thus, for a 0-supervertex 𝑣 ∈ 𝑉 = 𝑉0 ,
supp(𝑣) = flat0 (𝑣) = {𝑣},
and for a superedge 𝑒 ∈ 𝐸 ⊆ 𝑃∗ (𝑉0 ) we obtain
supp(𝑒) =

Ø

supp(𝑣) =

𝑣 ∈𝑒

Ø

{𝑣} = 𝑒.

𝑣 ∈𝑒

(⇒) Assume 𝐻 = (𝑉0 , 𝐸) is an interval hypergraph. Then there exists a total order ≤ on 𝑉0 such that for each
𝑒 ∈ 𝐸 there are 𝑥, 𝑦 ∈ 𝑉0 with 𝑥 ≤ 𝑦 and
𝑒 = [𝑥, 𝑦] ≤ .
Define 𝐻 (0) = (𝑉, 𝐸) with 𝑉 := 𝑉0 as above. For every 𝑒 ∈ 𝐸 we have seen that supp(𝑒) = 𝑒, so
supp(𝑒) = 𝑒 = [𝑥, 𝑦] ≤ .
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Chapter 4. Some Particular SuperHyperGraphs Hence 𝐻 (0) is an interval 0-SuperHyperGraph with respect to the same order ≤. (⇐) Conversely, suppose 𝐻 (0) = (𝑉, 𝐸) with 𝑉 = 𝑉0 is an interval 0-SuperHyperGraph. Then there exists a total order ≤ on 𝑉0 such that for every 𝑒 ∈ 𝐸 there are 𝑥, 𝑦 ∈ 𝑉0 with 𝑥 ≤ 𝑦 and supp(𝑒) = [𝑥, 𝑦] ≤ . But for 𝑛 = 0 we have supp(𝑒) = 𝑒, so 𝑒 = [𝑥, 𝑦] ≤ for all 𝑒 ∈ 𝐸. Therefore 𝐻 = (𝑉0 , 𝐸) is an interval hypergraph in the usual sense. This proves the equivalence, and shows that when 𝑛 = 0, interval 𝑛-SuperHyperGraphs coincide exactly with interval hypergraphs, so the former constitute a genuine generalization of the latter. □ 4.18 Unimodular SuperHypergraphs A unimodular function is a function whose values have absolute value one, typically complex-valued, e.g., | 𝑓 (𝑥)| = 1 everywhere. A unimodular graph has a totally unimodular incidence matrix, so related linear programs have integral optimal solutions (cf. [476, 477]). An unimodular hypergraph has a totally unimodular incidence matrix, so all subdeterminants are restricted to minus one, zero, or one [17,478–480]. Unimodular 𝑛SuperHyperGraphs have totally unimodular incidence matrices, ensuring integer solutions in associated linear programming and combinatorial optimization problems and algorithms. Definition 4.18.1 (Totally unimodular matrix). Let 𝐴 be a real matrix. We say that 𝐴 is totally unimodular if every square submatrix of 𝐴 has determinant in {−1, 0, 1}. Example 4.18.2 (Totally unimodular matrix). Consider the 3 × 3 identity matrix 1 © 𝐴 = 0 «0 0 1 0 0 ª 0® . 1¬ Every square submatrix of 𝐴 is either a smaller identity matrix (or one of its permutations) or a matrix containing a zero row or zero column. Hence every such determinant is 1, 0, or −1. Therefore 𝐴 is a totally unimodular matrix. Definition 4.18.3 (Unimodular hypergraph). [17] Let 𝐻 = (𝑉, 𝐸) be a (finite) hypergraph, where 𝑉 = {𝑣 1 , . . . , 𝑣 𝑛 } and 𝐸 = {𝑒 1 , . . . , 𝑒 𝑚 }, and let 𝐴(𝐻) = (𝑎 𝑖 𝑗 ) be its incidence matrix defined by ( 1, if 𝑣 𝑖 ∈ 𝑒 𝑗 , 𝑎 𝑖 𝑗 := 0, otherwise. The hypergraph 𝐻 is called unimodular if its incidence matrix 𝐴(𝐻) is totally unimodular. A concrete example is given below. Example 4.18.4 (Unimodular hypergraph). Let 𝑉 := {𝑣 1 , 𝑣 2 }, 𝐸 := {𝑒 1 , 𝑒 2 }, 𝑒 1 := {𝑣 1 }, 𝑒 2 := {𝑣 2 }. with hyperedges The incidence matrix 𝐴(𝐻) of the hypergraph 𝐻 = (𝑉, 𝐸) is 1 0 𝐴(𝐻) = . 0 1 This is the 2 × 2 identity matrix, which is totally unimodular (since all its square subdeterminants are 0 or 1). Hence 𝐻 is a unimodular hypergraph. 98

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#p268

100.

Chapter 4. Some Particular SuperHyperGraphs Definition 4.18.5 (𝑛-SuperHyperGraph incidence matrix). Let 𝑉0 be a finite base set and 𝑛 ∈ N0 . An 𝑛-SuperHyperGraph is a triple H (𝑛) = (𝑉, 𝐸, 𝜕), where • 𝑉 ⊆ 𝑃𝑛 (𝑉0 ) is a finite set of 𝑛-supervertices, • 𝐸 is a finite set of 𝑛-superedges, • 𝜕 : 𝐸 → P∗ (𝑉) is the incidence map, with P∗ (𝑉) := P (𝑉) \ {∅}. Enumerate 𝑉 = {𝑤 1 , . . . , 𝑤 𝑁 } and 𝐸 = { 𝑓1 , . . . , 𝑓 𝑀 }. The incidence matrix of H (𝑛) is the 𝑁 × 𝑀 matrix 𝐴(H (𝑛) ) = (𝑏 𝑖 𝑗 ) defined by ( 1, if 𝑤 𝑖 ∈ 𝜕 ( 𝑓 𝑗 ), 𝑏 𝑖 𝑗 := 0, otherwise. A concrete example is given below. Example 4.18.6 (1-SuperHyperGraph incidence matrix). Let the base set be 𝑉0 := {𝑎, 𝑏, 𝑐}, so that the first powerset is P1 (𝑉0 ) = P(𝑉0 ). Define the set of 1-supervertices 𝑉 := 𝑤 1 , 𝑤 2 := {𝑎, 𝑏}, {𝑏, 𝑐} ⊆ P1 (𝑉0 ), and the set of 1-superedges 𝐸 := { 𝑓1 , 𝑓2 }, with incidence map 𝜕 : 𝐸 → P∗ (𝑉) given by 𝜕 ( 𝑓1 ) := {𝑤 1 , 𝑤 2 }, 𝜕 ( 𝑓2 ) := {𝑤 2 }. Enumerating 𝑉 = {𝑤 1 , 𝑤 2 } and 𝐸 = { 𝑓1 , 𝑓2 }, the incidence matrix 𝐴(H (1) ) = (𝑏 𝑖 𝑗 ) of the 1-SuperHyperGraph H (1) = (𝑉, 𝐸, 𝜕) is 𝑏 11 𝑏 12 1 0 (1) 𝐴(H ) = = , 𝑏 21 𝑏 22 1 1 because 𝑤 1 ∈ 𝜕 ( 𝑓1 ), 𝑤 1 ∉ 𝜕 ( 𝑓2 ), and 𝑤 2 ∈ 𝜕 ( 𝑓1 ) ∩ 𝜕 ( 𝑓2 ). Definition 4.18.7 (Unimodular 𝑛-SuperHyperGraph). Let H (𝑛) = (𝑉, 𝐸, 𝜕) be an 𝑛-SuperHyperGraph with incidence matrix 𝐴(H (𝑛) ) as above. We say that H (𝑛) is unimodular if 𝐴(H (𝑛) ) is totally unimodular. Example 4.18.8 (Unimodular 1-SuperHyperGraph). Let the base set be 𝑉0 := {𝑎, 𝑏}, so that P1 (𝑉0 ) = P(𝑉0 ). Define the 1-supervertex set 𝑉 := 𝑤 1 , 𝑤 2 := {𝑎}, {𝑏} ⊆ P1 (𝑉0 ), and the 1-superedge set 𝐸 := { 𝑓1 , 𝑓2 }, with incidence map 𝜕 ( 𝑓1 ) := {𝑤 1 }, 𝜕 ( 𝑓2 ) := {𝑤 2 }. Enumerating 𝑉 = {𝑤 1 , 𝑤 2 } and 𝐸 = { 𝑓1 , 𝑓2 }, the incidence matrix of the 1-SuperHyperGraph H (1) = (𝑉, 𝐸, 𝜕) is 1 0 (1) 𝐴(H ) = . 0 1 This is the 2 × 2 identity matrix, hence it is totally unimodular. SuperHyperGraph. 99 Therefore H (1) is a unimodular 1-

101.

Chapter 4. Some Particular SuperHyperGraphs Feature Unimodular hypergraph 𝐻 = (𝑉, 𝐸) [17] Underlying universe A finite vertex set 𝑉 Vertices Edges / superedges Ordinary vertices 𝑣 ∈ 𝑉 Hyperedges 𝑒 ∈ 𝐸 with 𝑒 ⊆ 𝑉 Incidence matrix Unimodularity condition Meaning of total unimodularity Reduction / generalization 𝐴(𝐻) = (𝑎 𝑖 𝑗 ), 𝑎 𝑖 𝑗 = 1 ⇔ 𝑣 𝑖 ∈ 𝑒 𝑗 𝐻 is unimodular iff 𝐴(𝐻) is totally unimodular Every square subdeterminant of 𝐴(𝐻) lies in {−1, 0, 1} Base notion (level 0) Typical implication (informal) LP relaxations associated with incidence constraints often have integral optima Unimodular 𝑛-SuperHyperGraph H (𝑛) = (𝑉, 𝐸, 𝜕) A finite base set 𝑉0 and iterated powerset level 𝑉 ⊆ 𝑃𝑛 (𝑉0 ) 𝑛-supervertices 𝑤 ∈ 𝑉 ⊆ 𝑃𝑛 (𝑉0 ) 𝑛-superedges 𝑓 ∈ 𝐸 with incidence map 𝜕 ( 𝑓 ) ∈ P (𝑉) \ {∅} 𝐴(H (𝑛) ) = (𝑏 𝑖 𝑗 ), 𝑏 𝑖 𝑗 = 1 ⇔ 𝑤 𝑖 ∈ 𝜕 ( 𝑓 𝑗 ) H (𝑛) is unimodular iff 𝐴(H (𝑛) ) is totally unimodular Every square subdeterminant of 𝐴(H (𝑛) ) lies in {−1, 0, 1} Extends unimodular hypergraphs: 𝑛 = 0 (with 𝜕 (𝑒) = 𝑒) recovers 𝐴(H (0) ) = 𝐴(𝐻) Same integrality benefit, now for higher-level (supervertex/superedge) incidence constraints Table 4.10: Concise comparison of unimodular hypergraphs and unimodular 𝑛-SuperHyperGraphs. Theorem 4.18.9 (Unimodular 𝑛-SuperHyperGraphs generalize unimodular hypergraphs). Let 𝐻 = (𝑉, 𝐸) be a finite hypergraph with incidence matrix 𝐴(𝐻). Regard 𝐻 as a 0-SuperHyperGraph H (0) := (𝑉, 𝐸, 𝜕), where 𝜕 (𝑒) = 𝑒 for each 𝑒 ∈ 𝐸. Then 𝐻 is a unimodular hypergraph ⇐⇒ H (0) is a unimodular 0-SuperHyperGraph. In particular, the notion of unimodularity for 𝑛-SuperHyperGraphs extends the usual notion of unimodular hypergraphs. Proof. By construction, the incidence matrix 𝐴(H (0) ) of the 0-SuperHyperGraph H (0) coincides with the incidence matrix 𝐴(𝐻) of the hypergraph 𝐻, entry by entry: for all 𝑖, 𝑗, 𝐴(H (0) )𝑖 𝑗 = 1 ⇐⇒ 𝑣 𝑖 ∈ 𝜕 (𝑒 𝑗 ) = 𝑒 𝑗 ⇐⇒ 𝐴(𝐻)𝑖 𝑗 = 1, and similarly for 0. Therefore 𝐴(𝐻) is totally unimodular if and only if 𝐴(H (0) ) is totally unimodular. By the definitions of unimodular hypergraph and unimodular 𝑛-SuperHyperGraph, this is equivalent to the desired statement. □ A comparison of unimodular hypergraphs and unimodular 𝑛-SuperHyperGraphs is presented in Table 4.10. 4.19 Probabilistic Superhypergraphs A probabilistic graph assigns probabilities to vertices or edges, representing uncertain existence or interactions and enabling stochastic inference and analysis [481–483]. Moreover, as a related concept to probabilistic graphs, the probabilistic directed graph [484, 485] is well known. A probabilistic hypergraph models hyperedges with vertex-level connection probabilities, capturing uncertain multiway interactions, weights, and affinitybased structure in complex networks [76, 486–488]. A probabilistic superhypergraph extends hypergraphs to hierarchical supervertices, assigning probabilities to multi-level superedges, modeling uncertain interactions across nested structures robustly [489]. The relevant definitions and related notions are presented below. Definition 4.19.1 (Probabilistic Hypergraph). [76, 486–488] Let 𝑉 be a finite, nonempty set and let P (𝑉) denote its powerset. A probabilistic hypergraph is a triplet 𝐻 = (𝑉, 𝐸, 𝐴), where 100

102.

Chapter 4. Some Particular SuperHyperGraphs • 𝐸 ⊆ P (𝑉) \ {∅} is a finite family of nonempty hyperedges; • 𝐴 : 𝑉 × 𝑉 → [0, 1] is an affinity (or probability) function, where 𝐴(𝑢, 𝑣) encodes the probability or similarity of a connection between 𝑢 and 𝑣. For each hyperedge 𝑒 ∈ 𝐸 we choose a centroid vertex 𝑐(𝑒) ∈ 𝑒 according to a specified optimality criterion, for example ∑︁ 𝑐(𝑒) := arg max 𝐴(𝑤, 𝑢). 𝑤 ∈𝑒 𝑢∈𝑒 The incidence matrix of 𝐻 is the |𝑉 | × |𝐸 | matrix H : 𝑉 × 𝐸 −→ [0, 1] defined by ( H(𝑣, 𝑒) := 𝐴 𝑐(𝑒), 𝑣 , if 𝑣 ∈ 𝑒, 0, if 𝑣 ∉ 𝑒. The weight of a hyperedge 𝑒 ∈ 𝐸 is ∑︁ 𝑤(𝑒) := 𝐴 𝑐(𝑒), 𝑣 , 𝑣 ∈𝑒 the degree of a vertex 𝑣 ∈ 𝑉 is 𝑑 (𝑣) := ∑︁ 𝑤(𝑒) H(𝑣, 𝑒), 𝑒∈𝐸 and the degree of a hyperedge 𝑒 ∈ 𝐸 is 𝛿(𝑒) := ∑︁ H(𝑣, 𝑒). 𝑣 ∈𝑒 Example 4.19.2 (A small probabilistic hypergraph). Let the finite vertex set be 𝑉 := {𝑎, 𝑏, 𝑐}, and define the family of hyperedges by 𝐸 := {𝑒 1 , 𝑒 2 }, 𝑒 1 := {𝑎, 𝑏}, 𝑒 2 := {𝑏, 𝑐}. Thus 𝐸 ⊆ P (𝑉) \ {∅}. Define the affinity (probability) function 𝐴 : 𝑉 × 𝑉 −→ [0, 1] by the table 𝑎 𝐴(𝑢, 𝑣) 𝑢,𝑣 ∈𝑉 = 𝑏 𝑐 𝑎 1.0 0.5 0.4 𝑏 0.8 1.0 0.3 𝑐 0.2 . 0.9 1.0 For each hyperedge 𝑒 ∈ 𝐸 we choose a centroid 𝑐(𝑒) := arg max ∑︁ 𝐴(𝑤, 𝑢). 𝑤 ∈𝑒 𝑢∈𝑒 For 𝑒 1 = {𝑎, 𝑏} we compute ∑︁ 𝐴(𝑎, 𝑢) = 𝐴(𝑎, 𝑎) + 𝐴(𝑎, 𝑏) = 1.0 + 0.8 = 1.8, 𝑢∈𝑒1 101

103.

[beta]

Chapter 4. Some Particular SuperHyperGraphs
∑︁

𝐴(𝑏, 𝑢) = 𝐴(𝑏, 𝑎) + 𝐴(𝑏, 𝑏) = 0.5 + 1.0 = 1.5,

𝑢∈𝑒1

so 𝑐(𝑒 1 ) = 𝑎.
For 𝑒 2 = {𝑏, 𝑐} we compute
∑︁

𝐴(𝑏, 𝑢) = 𝐴(𝑏, 𝑏) + 𝐴(𝑏, 𝑐) = 1.0 + 0.9 = 1.9,

𝑢∈𝑒2

∑︁

𝐴(𝑐, 𝑢) = 𝐴(𝑐, 𝑏) + 𝐴(𝑐, 𝑐) = 0.3 + 1.0 = 1.3,

𝑢∈𝑒2

hence 𝑐(𝑒 2 ) = 𝑏.
The incidence matrix H : 𝑉 × 𝐸 → [0, 1] is
(
H(𝑣, 𝑒) :=


𝐴 𝑐(𝑒), 𝑣 ,

if 𝑣 ∈ 𝑒,

0,

if 𝑣 ∉ 𝑒,

so explicitly
𝑎
H=
𝑏
𝑐

𝑒1
𝐴(𝑐(𝑒 1 ), 𝑎)
𝐴(𝑐(𝑒 1 ), 𝑏)
0

𝑒2
1.0
0
©
= 0.8
𝐴(𝑐(𝑒 2 ), 𝑏)
«0
𝐴(𝑐(𝑒 2 ), 𝑐)

0
ª
1.0® .
0.9¬

The hyperedge weights are
𝑤(𝑒 1 ) =

∑︁


𝐴 𝑐(𝑒 1 ), 𝑣 = 𝐴(𝑎, 𝑎) + 𝐴(𝑎, 𝑏) = 1.0 + 0.8 = 1.8,

𝑣 ∈𝑒1

𝑤(𝑒 2 ) =

∑︁


𝐴 𝑐(𝑒 2 ), 𝑣 = 𝐴(𝑏, 𝑏) + 𝐴(𝑏, 𝑐) = 1.0 + 0.9 = 1.9.

𝑣 ∈𝑒2

The degrees of vertices (in the sense of the definition) are
𝑑 (𝑎) = 𝑤(𝑒 1 ) H(𝑎, 𝑒 1 ) = 1.8 · 1.0 = 1.8,
𝑑 (𝑏) = 𝑤(𝑒 1 ) H(𝑏, 𝑒 1 ) + 𝑤(𝑒 2 ) H(𝑏, 𝑒 2 ) = 1.8 · 0.8 + 1.9 · 1.0 = 1.44 + 1.9 = 3.34,
𝑑 (𝑐) = 𝑤(𝑒 2 ) H(𝑐, 𝑒 2 ) = 1.9 · 0.9 = 1.71.
Thus 𝐻 = (𝑉, 𝐸, 𝐴) is a concrete probabilistic hypergraph in the sense of the definition.
Definition 4.19.3 (Probabilistic 𝑛-SuperHyperGraph). [489] Let 𝑉0 be a finite, nonempty base set. For each
integer 𝑘 ≥ 0, define the iterated powersets

P0 (𝑉0 ) := 𝑉0 ,
P 𝑘+1 (𝑉0 ) := P P 𝑘 (𝑉0 ) ,
where P(𝑋) denotes the powerset of a set 𝑋.
Fix a level 𝑛 ∈ N0 . A probabilistic 𝑛-SuperHyperGraph over 𝑉0 is a triplet
𝐺 = (𝑉, 𝐸, 𝐴),
where
• 𝑉 ⊆ P𝑛 (𝑉0 ) is a finite set of 𝑛-supervertices;
• 𝐸 ⊆ P (𝑉) \ {∅} is a finite family of nonempty 𝑛-superedges, each 𝑒 ∈ 𝐸 being a nonempty subset of 𝑉;
• 𝐴 : 𝑉 × 𝑉 → [0, 1] is an affinity (or probability) function on pairs of 𝑛-supervertices, where 𝐴(𝑢, 𝑣)
encodes the probability or similarity of an interaction between 𝑢 and 𝑣.
102

#p283

104.

Chapter 4. Some Particular SuperHyperGraphs For each 𝑛-superedge 𝑒 ∈ 𝐸 we choose a centroid 𝑛-supervertex 𝑐(𝑒) ∈ 𝑒 according to ∑︁ 𝐴(𝑤, 𝑢). 𝑐(𝑒) := arg max 𝑤 ∈𝑒 𝑢∈𝑒 The incidence matrix of 𝐺 is the |𝑉 | × |𝐸 | matrix H : 𝑉 × 𝐸 −→ [0, 1] defined by ( H(𝑣, 𝑒) := 𝐴 𝑐(𝑒), 𝑣 , if 𝑣 ∈ 𝑒, 0, if 𝑣 ∉ 𝑒. The weight of an 𝑛-superedge 𝑒 ∈ 𝐸 is ∑︁ 𝑤(𝑒) := 𝐴 𝑐(𝑒), 𝑣 , 𝑣 ∈𝑒 the degree of an 𝑛-supervertex 𝑣 ∈ 𝑉 is 𝑑 (𝑣) := ∑︁ 𝑤(𝑒) H(𝑣, 𝑒), 𝑒∈𝐸 and the degree of an 𝑛-superedge 𝑒 ∈ 𝐸 is 𝛿(𝑒) := ∑︁ H(𝑣, 𝑒). 𝑣 ∈𝑒 When 𝑛 = 0, this definition reduces to that of a probabilistic hypergraph with vertex set 𝑉0 . Example 4.19.4 (A probabilistic 2-SuperHyperGraph). Let the finite base set be 𝑉0 := {𝑥1 , 𝑥2 , 𝑥3 }. Then P1 (𝑉0 ) = P(𝑉0 ), P2 (𝑉0 ) = P P(𝑉0 ) . 𝑣 1 := {𝑥1 , 𝑥2 } , 𝑣 2 := {𝑥 2 , 𝑥3 } . Define two 2-supervertices Since {𝑥 1 , 𝑥2 }, {𝑥2 , 𝑥3 } ∈ P1 (𝑉0 ), both 𝑣 1 and 𝑣 2 are subsets of P1 (𝑉0 ), hence 𝑣 1 , 𝑣 2 ∈ P P1 (𝑉0 ) = P2 (𝑉0 ). Set the 2-supervertex set 𝑉 := {𝑣 1 , 𝑣 2 } ⊆ P2 (𝑉0 ). Introduce a single 2-superedge 𝑒 1 := {𝑣 1 , 𝑣 2 }, 𝐸 := {𝑒 1 } ⊆ P (𝑉) \ {∅}. Define the affinity function 𝐴 : 𝑉 × 𝑉 −→ [0, 1] by 𝐴(𝑢, 𝑣) 𝑢,𝑣 ∈𝑉 = 𝑣 1 𝑣2 103 𝑣1 1.0 0.3 𝑣2 0.6 . 1.0

105.

Chapter 4. Some Particular SuperHyperGraphs For the unique 2-superedge 𝑒 1 = {𝑣 1 , 𝑣 2 } we choose the centroid ∑︁ 𝑐(𝑒 1 ) := arg max 𝐴(𝑤, 𝑢). 𝑤 ∈𝑒1 𝑢∈𝑒1 We compute ∑︁ 𝐴(𝑣 1 , 𝑢) = 𝐴(𝑣 1 , 𝑣 1 ) + 𝐴(𝑣 1 , 𝑣 2 ) = 1.0 + 0.6 = 1.6, 𝑢∈𝑒1 ∑︁ 𝐴(𝑣 2 , 𝑢) = 𝐴(𝑣 2 , 𝑣 1 ) + 𝐴(𝑣 2 , 𝑣 2 ) = 0.3 + 1.0 = 1.3, 𝑢∈𝑒1 so 𝑐(𝑒 1 ) = 𝑣 1 . The incidence matrix H : 𝑉 × 𝐸 → [0, 1] is given by ( 𝐴 𝑐(𝑒), 𝑣 , H(𝑣, 𝑒) := 0, if 𝑣 ∈ 𝑒, if 𝑣 ∉ 𝑒, hence H = 𝑣1 𝑣2 𝑒1 1.0 . 𝐴(𝑐(𝑒 1 ), 𝑣 1 ) = 0.6 𝐴(𝑐(𝑒 1 ), 𝑣 2 ) The weight of the 2-superedge 𝑒 1 is ∑︁ 𝐴 𝑐(𝑒 1 ), 𝑣 = 𝐴(𝑣 1 , 𝑣 1 ) + 𝐴(𝑣 1 , 𝑣 2 ) = 1.0 + 0.6 = 1.6. 𝑤(𝑒 1 ) = 𝑣 ∈𝑒1 The degrees of the 2-supervertices are 𝑑 (𝑣 1 ) = 𝑤(𝑒 1 ) H(𝑣 1 , 𝑒 1 ) = 1.6 · 1.0 = 1.6, 𝑑 (𝑣 2 ) = 𝑤(𝑒 1 ) H(𝑣 2 , 𝑒 1 ) = 1.6 · 0.6 = 0.96. Thus 𝐺 := (𝑉, 𝐸, 𝐴) is a concrete probabilistic 2-SuperHyperGraph over the base set 𝑉0 , in the sense of the given definition. We include in Table 4.11 a comparison of probabilistic graphs, probabilistic hypergraphs, and probabilistic n-SuperHyperGraphs. 4.20 Balanced SuperHypergraphs A balanced 𝑛-SuperHyperGraph is one whose incidence matrix contains no odd-order square submatrix in which every row and column has exactly two entries equal to 1. This condition guarantees even-cycle parity and ensures structural stability across its multi-level superedge connections. A balanced 𝑛-SuperHyperGraph is an applied generalization of the classical notions of balanced graphs and balanced hypergraphs (cf. [17,490–492]). Related concepts are also known, such as balanced fuzzy graphs [493, 494], balanced intuitinistic fuzzy graphs [495, 496], balanced directed graphs [497, 498], balanced picture fuzzy graphs [499], and balanced neutrosophic graphs [500]. The relevant definitions and related notions are presented below. Definition 4.20.1 (Balanced {0, 1}–matrix). [17] A {0, 1}–matrix 𝐴 is called balanced if it does not contain, as a square submatrix, any odd–order matrix 𝐵 such that every row and every column of 𝐵 has exactly two entries equal to 1. Equivalently, for every square submatrix 𝐵 of 𝐴 with exactly two 1’s in each row and each column, the order of 𝐵 must be even. 104

106.

[beta]

Chapter 4. Some Particular SuperHyperGraphs
Table 4.11: Comparison of probabilistic graphs, probabilistic hypergraphs, and probabilistic 𝑛SuperHyperGraphs
Framework

Underlying structure

Probabilistic / affinity modeling

Probabilistic graph

Simple graph 𝐺 = (𝑉, 𝐸) (or potential edges on 𝑉 × 𝑉).

Probabilistic hypergraph

Hypergraph 𝐻 = (𝑉, 𝐸) with hyperedges 𝑒 ∈ 𝐸 ⊆ P∗ (𝑉).

Probabilistic
SuperHyperGraph

𝑛-SuperHyperGraph 𝐺 = (𝑉, 𝐸) with
𝑉 ⊆ P𝑛 (𝑉0 ) and 𝐸 ⊆ P∗ (𝑉).

A probability or affinity function 𝑃 :
𝑉 × 𝑉 → [0, 1] assigns to each vertex
pair the likelihood or strength of an
edge.
An affinity function 𝐴 : 𝑉 × 𝑉 →
[0, 1] encodes pairwise probabilities
inside hyperedges; centroids, incidence matrix, and hyperedge weights
are derived from 𝐴.
An affinity function 𝐴 : 𝑉 ×
𝑉 → [0, 1] on 𝑛-supervertices induces probabilistic incidence, superedge weights, and degrees across
hierarchical, multi-level interactions.

𝑛-

Example 4.20.2 (Balanced {0, 1}–matrix). Consider the 3 × 3 matrix
1
©
𝐴 = 0
«0

0
1
0

0
ª
0® .
1¬

Any square submatrix of 𝐴 is either a (smaller) identity matrix or a matrix with at most one entry equal to 1 in
each row or column. In particular, no odd–order square submatrix of 𝐴 has exactly two entries equal to 1 in
every row and every column. Hence 𝐴 is a balanced {0, 1}–matrix.
Definition 4.20.3 (Balanced hypergraph). [17] Let 𝐻 = (𝑉, 𝐸) be a finite hypergraph and let 𝐴(𝐻) denote its
incidence matrix (as defined previously). The hypergraph 𝐻 is called balanced if the matrix 𝐴(𝐻) is balanced
in the sense above.
Example 4.20.4 (Balanced hypergraph). Let
𝑉 := {𝑣 1 , 𝑣 2 , 𝑣 3 },

𝐸 := {𝑒 1 , 𝑒 2 },

𝑒 1 := {𝑣 1 , 𝑣 2 },

𝑒 2 := {𝑣 2 , 𝑣 3 }.

with hyperedges
The incidence matrix of the hypergraph 𝐻 = (𝑉, 𝐸) is
1
©
𝐴(𝐻) = 1
«0

0
ª
1® .
1¬

Every 1 × 1 or 2 × 2 square submatrix of 𝐴(𝐻) has at most two entries equal to 1 in total, so none of them
has exactly two 1’s in each row and each column. Therefore 𝐴(𝐻) does not contain any odd–order square
submatrix with two 1’s in every row and column. Thus 𝐴(𝐻) is balanced, and the hypergraph 𝐻 is a balanced
hypergraph.
Definition 4.20.5 (Balanced 𝑛-SuperHyperGraph). Let H (𝑛) = (𝑉, 𝐸, 𝜕) be an 𝑛-SuperHyperGraph with
incidence matrix 𝐴(H (𝑛) ) (as defined previously). We say that H (𝑛) is a balanced 𝑛-SuperHyperGraph if
𝐴(H (𝑛) ) is a balanced {0, 1}–matrix.
Example 4.20.6 (Balanced 1-SuperHyperGraph). Let the base set be
𝑉0 := {𝑎, 𝑏},
so that P1 (𝑉0 ) = P(𝑉0 ). Define the set of 1–supervertices


𝑉 := 𝑤 1 , 𝑤 2 := {𝑎}, {𝑏} ⊆ P1 (𝑉0 ),
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Chapter 4. Some Particular SuperHyperGraphs Underlying universe Balanced hypergraph 𝐻 = (𝑉, 𝐸) [17, 490– 492] Finite vertex set 𝑉 Vertices Edges / superedges Ordinary vertices 𝑣 ∈ 𝑉 Hyperedges 𝑒 ∈ 𝐸 ⊆ P (𝑉) \ {∅} Incidence matrix Balancedness criterion (matrix form) Combinatorial intuition (informal) 𝐴(𝐻) = (𝑎 𝑖 𝑗 ), 𝑎 𝑖 𝑗 = 1 ⇔ 𝑣 𝑖 ∈ 𝑒 𝑗 𝐴(𝐻) has no odd-order square submatrix with exactly two 1’s in each row and column Excludes “odd cycles” in the incidence structure encoded by 𝐴(𝐻) Reduction / generalization Base notion (level 0) Feature Balanced 𝑛-SuperHyperGraph H (𝑛) = (𝑉, 𝐸, 𝜕) Finite base set 𝑉0 and level-𝑛 supervertex set 𝑉 ⊆ 𝑃𝑛 (𝑉0 ) 𝑛-supervertices 𝑤 ∈ 𝑉 ⊆ 𝑃𝑛 (𝑉0 ) 𝑛-superedges 𝑓 ∈ 𝐸 with incidence map 𝜕 ( 𝑓 ) ∈ P (𝑉) \ {∅} 𝐴(H (𝑛) ) = (𝑏 𝑖 𝑗 ), 𝑏 𝑖 𝑗 = 1 ⇔ 𝑤 𝑖 ∈ 𝜕 ( 𝑓 𝑗 ) 𝐴(H (𝑛) ) has no odd-order square submatrix with exactly two 1’s in each row and column Enforces the same even-parity restriction across multi-level incidences of supervertices and superedges Extends balanced hypergraphs: for 𝑛 = 0 with 𝜕 (𝑒) = 𝑒, one has 𝐴(H (0) ) = 𝐴(𝐻) Table 4.12: Concise comparison of balanced hypergraphs and balanced 𝑛-SuperHyperGraphs. and the set of 1–superedges 𝐸 := { 𝑓1 , 𝑓2 }, with incidence map 𝜕 ( 𝑓1 ) := {𝑤 1 }, 𝜕 ( 𝑓2 ) := {𝑤 2 }. Enumerating 𝑉 = {𝑤 1 , 𝑤 2 } and 𝐸 = { 𝑓1 , 𝑓2 }, the incidence matrix of the 1–SuperHyperGraph H (1) = (𝑉, 𝐸, 𝜕) is 1 0 (1) 𝐴 H = . 0 1 This is the 2 × 2 identity matrix. As in the first example, no odd–order square submatrix of 𝐴 H (1) has two 1’s in every row and every column. Hence 𝐴 H (1) is a balanced {0, 1}–matrix, and H (1) is a balanced 1–SuperHyperGraph. Theorem 4.20.7 (Balanced 𝑛-SuperHyperGraphs generalize balanced hypergraphs). Let 𝐻 = (𝑉, 𝐸) be a finite hypergraph. Regard 𝐻 as a 0-SuperHyperGraph H (0) := (𝑉, 𝐸, 𝜕), where 𝜕 (𝑒) = 𝑒 for all 𝑒 ∈ 𝐸. Then 𝐻 is a balanced hypergraph ⇐⇒ H (0) is a balanced 0-SuperHyperGraph. In particular, the notion of a balanced 𝑛-SuperHyperGraph extends the classical notion of a balanced hypergraph, which is recovered by taking 𝑛 = 0. Proof. By construction, the incidence matrix of the 0-SuperHyperGraph H (0) coincides with the incidence matrix of 𝐻: 𝐴(H (0) ) = 𝐴(𝐻), entrywise. Therefore 𝐴(𝐻) is balanced if and only if 𝐴(H (0) ) is balanced. By the definitions above, this is equivalent to 𝐻 being a balanced hypergraph and H (0) being a balanced 0-SuperHyperGraph, respectively. □ A comparison of balanced hypergraphs and balanced 𝑛-SuperHyperGraphs is presented in Table 4.12. 4.21 Spatial Superhypergraphs Spatial hypergraph assigns each vertex a distinct point in Euclidean space, modeling multiway relationships constrained by geometric or geographic structure [501–504]. Spatial SuperHypergraph embeds base elements in space, while higher-level supervertices and superedges capture hierarchical, multi-scale relationships across locations and regions [504]. The relevant definitions and related notions are presented below. 106

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Definition 4.21.1 (Spatial hypergraph). [504] Let 𝑑 ∈ N and let 𝑉 be a finite, nonempty set. A hypergraph on
𝑉 is a pair
𝐻 := (𝑉, 𝐸),
𝐸 ⊆ P∗ (𝑉) := P (𝑉) \ {∅},
whose elements 𝑒 ∈ 𝐸 are called hyperedges.
A 𝑑-dimensional spatial hypergraph is a triple
SpHG := (𝑉, 𝐸, 𝜆),
where
• (𝑉, 𝐸) is a hypergraph as above;
• 𝜆 : 𝑉 → R𝑑 is an embedding map that assigns to each vertex 𝑣 ∈ 𝑉 a point 𝜆(𝑣) in Euclidean space, and
is injective (no two vertices share the same location).
The pair (𝑉, 𝐸) captures the combinatorial structure, while 𝜆 endows the hypergraph with a fixed spatial
geometry.
Example 4.21.2 (Spatial hypergraph: wireless sensors in the plane). Let 𝑑 = 2 and consider three wireless
sensors located in the plane. Set the vertex set
𝑉 := {𝑠1 , 𝑠2 , 𝑠3 }.
Define the hyperedge family

𝐸 := 𝑒 1 , 𝑒 2 ,

𝑒 1 := {𝑠1 , 𝑠2 }, 𝑒 2 := {𝑠2 , 𝑠3 },

so that
𝐻 := (𝑉, 𝐸)
is a hypergraph in the above sense.
We now fix the physical positions of the sensors in R2 by an injective embedding map
𝜆 : 𝑉 −→ R2 ,
given by
𝜆(𝑠1 ) := (0, 0),

𝜆(𝑠2 ) := (1, 0),

𝜆(𝑠3 ) := (1, 1).

The triple
SpHG := (𝑉, 𝐸, 𝜆)
is a 2-dimensional spatial hypergraph. The combinatorial structure of group communication is encoded by 𝐸,
while the map 𝜆 records the spatial locations of the sensors.
Definition 4.21.3 (Spatial 𝑛-SuperHyperGraph). [504] Let 𝑑 ∈ N, let 𝑉0 be a finite base set, and let SHG (𝑛) =
(𝑉, 𝐸) be an 𝑛-SuperHyperGraph on 𝑉0 , that is
𝑉, 𝐸 ⊆ P 𝑛 (𝑉0 ).
A 𝑑-dimensional spatial 𝑛-SuperHyperGraph is a quadruple
SpSHG (𝑛) := (𝑉0 , 𝑉, 𝐸, 𝜆),
where
• (𝑉, 𝐸) is an 𝑛-SuperHyperGraph on 𝑉0 ;
• 𝜆 : 𝑉0 → R𝑑 is an injective embedding map that assigns to each base element 𝑥 ∈ 𝑉0 a fixed position
𝜆(𝑥) in Euclidean space.
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Thus the combinatorial hierarchy is encoded by (𝑉, 𝐸) ⊆ P 𝑛 (𝑉0 ), while the map 𝜆 equips all 𝑛-supervertices
and 𝑛-superedges (via their elements in 𝑉0 ) with a concrete spatial realization.

For 𝑛 = 1 and 𝑉 = {𝑣} : 𝑣 ∈ 𝑉0 , the structure SpSHG (1) reduces to a spatial hypergraph (𝑉0 , 𝐸, 𝜆) in the
sense of the previous definition.
Example 4.21.4 (Spatial 2-SuperHyperGraph: grouped facilities on a map). Let 𝑑 = 2 and let the finite base
set of facilities be
𝑉0 := {𝐴, 𝐵, 𝐶}.
We interpret these as three physical sites in the plane and fix their coordinates by an injective embedding map
𝜆 : 𝑉0 −→ R2 ,
for example
𝜆( 𝐴) := (0, 0),

𝜆(𝐵) := (2, 0),

𝜆(𝐶) := (2, 2).

Recall that
P0 (𝑉0 ) = 𝑉0 ,

P1 (𝑉0 ) = P(𝑉0 ),


P2 (𝑉0 ) = P P(𝑉0 ) .

Define two 2-supervertices by

𝑣 1 := {𝐴, 𝐵} ,


𝑣 2 := {𝐵, 𝐶} ,

so 𝑣 1 , 𝑣 2 ∈ P2 (𝑉0 ). Set
𝑉 := {𝑣 1 , 𝑣 2 } ⊆ P2 (𝑉0 ),
and define a single 2-superedge
𝑒 := {𝑣 1 , 𝑣 2 },

𝐸 := {𝑒} ⊆ P (𝑉) \ {∅}.

Then
SHG (2) := (𝑉, 𝐸)
is a 2-SuperHyperGraph on the base set 𝑉0 . The quadruple
SpSHG (2) := (𝑉0 , 𝑉, 𝐸, 𝜆)
is a 2-dimensional spatial 2-SuperHyperGraph.
Here:

• 𝑉0 are individual facilities with concrete positions 𝜆( 𝐴), 𝜆(𝐵), 𝜆(𝐶) in the plane;
• each 2-supervertex (such as 𝑣 1 ) is a small cluster of facility groups (e.g. a service bundle {𝐴, 𝐵});
• the 2-superedge 𝑒 links the clusters 𝑣 1 and 𝑣 2 , representing a higher-level relation (for example, a regional
planning zone that coordinates the two bundles).

Thus (𝑉, 𝐸) encodes the hierarchical combinatorial structure, while 𝜆 provides a spatial realization at the base
level 𝑉0 .
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Chapter 4. Some Particular SuperHyperGraphs 4.22 Planar SuperHypergraphs A planar graph is a finite graph drawable on the plane without edge crossings, using nonintersecting straight or curved edges [505–507]. As concepts related to planar graphs, notions such as quasi-planar graphs [508–510], planar digraphs [511, 512], co-planar graphs [513, 514], fuzzy planar graphs [515, 516], biplanar graphs [517, 518], and neutrosophic planar graphs [342, 519–521] are well known. Planar graphs are often not structurally complex, and because their edges do not cross, they offer high visual clarity for human interpretation. For this reason, the notion of planarity has been widely applied in many research papers. A planar hypergraph is a finite hypergraph whose incidence graph admits a planar embedding without edge crossings in the plane [17, 522]. A planar SuperHyperGraph is a finite SuperHyperGraph whose incidence graph can be embedded in the plane without any edge crossings. The relevant definitions and related notions are presented below. Definition 4.22.1 (Incidence graph of a hypergraph). Let 𝐻 = (𝑉, 𝐸) be a finite hypergraph with incidence map 𝜕 : 𝐸 → P∗ (𝑉). The incidence graph of 𝐻 is the bipartite graph 𝐵(𝐻) := (𝑉 ∪ 𝐸, 𝐹), where 𝐹 := {𝑣, 𝑒} ⊆ 𝑉 ∪ 𝐸 | 𝑒 ∈ 𝐸, 𝑣 ∈ 𝜕 (𝑒) . Example 4.22.2 (Incidence graph of a hypergraph). Let 𝑉 := {𝑣 1 , 𝑣 2 , 𝑣 3 }, 𝐸 := {𝑒 1 , 𝑒 2 }, 𝑒 1 := {𝑣 1 , 𝑣 2 }, 𝑒 2 := {𝑣 2 , 𝑣 3 }. with hyperedges Define the hypergraph 𝐻 = (𝑉, 𝐸) with the natural incidence map 𝜕 : 𝐸 → P∗ (𝑉) given by 𝜕 (𝑒 𝑖 ) = 𝑒 𝑖 . The incidence graph 𝐵(𝐻) = (𝑉 ∪ 𝐸, 𝐹) has vertex set 𝑉 ∪ 𝐸 = {𝑣 1 , 𝑣 2 , 𝑣 3 , 𝑒 1 , 𝑒 2 }, and edge set 𝐹 = {𝑣 1 , 𝑒 1 }, {𝑣 2 , 𝑒 1 }, {𝑣 2 , 𝑒 2 }, {𝑣 3 , 𝑒 2 } , since each pair {𝑣, 𝑒} is an edge of 𝐵(𝐻) exactly when 𝑣 ∈ 𝜕 (𝑒). Definition 4.22.3 (Planar hypergraph). [17, 522] A hypergraph 𝐻 = (𝑉, 𝐸) is called planar if its incidence graph 𝐵(𝐻) is a planar graph, i.e. it admits a drawing in the plane with no edge crossings. Example 4.22.4 (Planar hypergraph). Consider again the hypergraph 𝐻 = (𝑉, 𝐸) from the previous example, with 𝑉 = {𝑣 1 , 𝑣 2 , 𝑣 3 }, 𝐸 = {𝑒 1 , 𝑒 2 }, 𝑒 1 = {𝑣 1 , 𝑣 2 }, 𝑒 2 = {𝑣 2 , 𝑣 3 }. Its incidence graph 𝐵(𝐻) is the bipartite graph with vertex set {𝑣 1 , 𝑣 2 , 𝑣 3 , 𝑒 1 , 𝑒 2 } and edges {𝑣 1 , 𝑒 1 }, {𝑣 2 , 𝑒 1 }, {𝑣 2 , 𝑒 2 }, {𝑣 3 , 𝑒 2 }. This graph can be drawn in the plane without edge crossings, for instance by placing 𝑣 1 , 𝑣 2 , 𝑣 3 on a horizontal line and 𝑒 1 , 𝑒 2 above them and drawing straight-line edges. Hence 𝐵(𝐻) is planar and therefore 𝐻 is a planar hypergraph. Definition 4.22.5 (Incidence graph of an 𝑛-SuperHyperGraph). Let H (𝑛) = (𝑉, 𝐸, 𝜕) be an 𝑛-SuperHyperGraph, where 𝜕 : 𝐸 → P∗ (𝑉) is the incidence map (as defined earlier in the text). The incidence graph of H (𝑛) is the bipartite graph 𝐵 H (𝑛) := (𝑉 ∪ 𝐸, 𝐹 (𝑛) ), where 𝐹 (𝑛) := {𝑣, 𝑒} ⊆ 𝑉 ∪ 𝐸 | 𝑒 ∈ 𝐸, 𝑣 ∈ 𝜕 (𝑒) . 109

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Chapter 4. Some Particular SuperHyperGraphs Example 4.22.6 (Incidence graph of a 1-SuperHyperGraph). Let the base set be 𝑉0 := {𝑎, 𝑏}, and consider 𝑉 := 𝑤 1 , 𝑤 2 := {𝑎}, {𝑏} ⊆ P1 (𝑉0 ), as the set of 1-supervertices. Let 𝐸 := { 𝑓1 } with incidence map 𝜕 ( 𝑓1 ) := {𝑤 1 , 𝑤 2 }. Then H (1) = (𝑉, 𝐸, 𝜕) is a 1-SuperHyperGraph. Its incidence graph 𝐵 H (1) = (𝑉 ∪ 𝐸, 𝐹 (1) ) has vertex set 𝑉 ∪ 𝐸 = {𝑤 1 , 𝑤 2 , 𝑓1 } and edge set 𝐹 (1) = {𝑤 1 , 𝑓1 }, {𝑤 2 , 𝑓1 } , because 𝑤 𝑖 ∈ 𝜕 ( 𝑓1 ) for 𝑖 = 1, 2. Thus 𝐵 H (1) is a small star-shaped bipartite graph. Definition 4.22.7 (Planar 𝑛-SuperHyperGraph). An 𝑛-SuperHyperGraph H (𝑛) = (𝑉, 𝐸, 𝜕) is called planar if (𝑛) its incidence graph 𝐵 H is a planar graph. Example 4.22.8 (Planar 1-SuperHyperGraph). Consider the 1-SuperHyperGraph H (1) = (𝑉, 𝐸, 𝜕) from the previous example, with 𝑉 = {𝑤 1 , 𝑤 2 }, Its incidence graph 𝐵 H 2. (1) 𝐸 = { 𝑓1 }, 𝜕 ( 𝑓1 ) = {𝑤 1 , 𝑤 2 }. has vertices {𝑤 1 , 𝑤 2 , 𝑓1 } and edges {𝑤 1 , 𝑓1 } and {𝑤 2 , 𝑓1 }, which is a path of length Such a graph is clearly planar (it can be drawn as two line segments meeting at 𝑓1 without crossings). Hence H (1) is a planar 1-SuperHyperGraph. Theorem 4.22.9 (Planar 𝑛-SuperHyperGraphs generalize planar hypergraphs). Let 𝐻 = (𝑉, 𝐸) be a finite hypergraph. Regard 𝐻 as a 0-SuperHyperGraph H (0) := (𝑉, 𝐸, 𝜕), with the same incidence map 𝜕. Then 𝐻 is planar ⇐⇒ H (0) is a planar 0-SuperHyperGraph. Consequently, the notion of a planar 𝑛-SuperHyperGraph is a genuine extension of the classical notion of a planar hypergraph, which is recovered when 𝑛 = 0. Proof. By construction, the incidence graph of 𝐻 and that of H (0) coincide: 𝐵(𝐻) = 𝐵 H (0) as graphs, since bothhave vertex set 𝑉 ∪ 𝐸 and edges {𝑣, 𝑒} precisely when 𝑣 ∈ 𝜕 (𝑒). Therefore 𝐵(𝐻) is planar if and only if 𝐵 H (0) is planar. By the preceding definitions, this is equivalent to 𝐻 being a planar hypergraph and H (0) being a planar 0-SuperHyperGraph, respectively. □ A concise comparison of planar graphs, planar hypergraphs, and planar n-SuperHyperGraphs is presented in Table 4.13. 110

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Chapter 4. Some Particular SuperHyperGraphs Feature Planar graph 𝐺 = (𝑉, 𝐸) [505–507] Planar hypergraph 𝐻 = (𝑉, 𝐸) [17, 522] Underlying objects Vertices and edges (2-uniform incidence) 𝐺 admits a plane drawing with no edge crossings Not needed (can be used via subdivision) The graph itself Vertices and hyperedges (𝑘-ary incidence) Planarity criterion Incidence graph What “embeds in the plane” Reduction / generalization Special case of hypergraph (2-uniform) Incidence graph 𝐵(𝐻) is planar Planar 𝑛-SuperHyperGr (𝑉, 𝐸, 𝜕) 𝑛-supervertices (𝑉 ⊆ 𝑃𝑛 superedges with incidenc Incidence graph 𝐵(H (𝑛) ) Bipartite graph on 𝑉 ∪ 𝐸 with edges {𝑣, 𝑒} iff 𝑣 ∈ 𝑒 The bipartite incidence graph Bipartite graph on 𝑉 ∪ 𝐸 {𝑣, 𝑒} iff 𝑣 ∈ 𝜕 (𝑒) The bipartite incidence g Recovered from SuperHyperGraphs at level 𝑛 = 0 Generalizes planar hype 𝑛 = 0, 𝐵(H (0) ) = 𝐵(𝐻) Table 4.13: Concise comparison of planar graphs, planar hypergraphs, and planar 𝑛-SuperHyperGraphs. 4.23 Outerplanar SuperHypergraph An outerplanar graph is a planar graph that admits an embedding in which every vertex lies on the boundary of the outer face [523, 524]. Outerplanar graphs generalize the class of planar graphs, and several related variants have been studied, including fuzzy outerplanar graphs [525–529], neutrosophic outerplanar graphs [520], and outerplanar directed graphs [530–532]. Outerplanar graphs form a tractable planar subclass with strong structural characterizations, enabling efficient algorithms, clear embeddings, and useful bounds for width parameters and graph drawing applications (cf. [533, 534]). The relevant definitions and related notions are presented below. An outerplanar hypergraph is defined as a hypergraph whose incidence bipartite graph is outerplanar, so that all vertices can be placed on the outer face in some planar embedding [535, 536]. An outerplanar superhypergraph is a superhypergraph whose extended incidence graph—obtained by adding auxiliary links between hyperedges—admits an outerplanar embedding. In other words, the enriched incidence structure must remain outerplanar when drawn in the plane. Definition 4.23.1 (Outerplanar graph). [523, 524] A (finite, simple) graph 𝐺 = (𝑉, 𝐸) is outerplanar if there exists a plane embedding of 𝐺 in which every vertex of 𝐺 lies on the boundary of the unbounded (outer) face. Definition 4.23.2 (Incidence (bipartite) representation of a hypergraph). Let 𝐻 = (𝑉, E) be a (finite) hypergraph, where ∅ ∉ E ⊆ P (𝑉). Its incidence graph (or bipartite representation) is the bipartite graph 𝐵(𝐻) := 𝑉 ∪¤ E, 𝐹 , 𝐹 := {𝑣, 𝑒} : 𝑣 ∈ 𝑉, 𝑒 ∈ E, 𝑣 ∈ 𝑒 . Definition 4.23.3 (Outerplanar hypergraph). [535, 536] A hypergraph 𝐻 is outerplanar if its incidence graph 𝐵(𝐻) is an outerplanar graph. Example 4.23.4 (An outerplanar hypergraph (via the incidence graph)). Let 𝑉 := {𝑣 1 , 𝑣 2 , 𝑣 3 , 𝑣 4 }, E := {𝑒 1 , 𝑒 2 }, 𝑒 1 := {𝑣 1 , 𝑣 2 , 𝑣 3 }, 𝑒 2 := {𝑣 3 , 𝑣 4 }. where Define the hypergraph 𝐻 := (𝑉, E). Its incidence graph is ¤ 𝐹 , 𝐵(𝐻) = 𝑉 ∪E, 𝐹 = {𝑣 1 , 𝑒 1 }, {𝑣 2 , 𝑒 1 }, {𝑣 3 , 𝑒 1 }, {𝑣 3 , 𝑒 2 }, {𝑣 4 , 𝑒 2 } . Observe that 𝐵(𝐻) is a tree (it has no cycles). Since every tree is outerplanar (one can embed it in the plane with all vertices on the boundary of the outer face), it follows that 𝐵(𝐻) is outerplanar. Hence 𝐻 is an outerplanar hypergraph in the sense of Definition (Outerplanar hypergraph). Definition 4.23.5 (Shadow of a hypergraph). Let 𝐻 = (𝑉, E) be a hypergraph. Its shadow (or 2-section) is the graph 𝜕 (𝐻) := 𝑉, {{𝑢, 𝑣} : 𝑢 ≠ 𝑣, ∃𝑒 ∈ E with {𝑢, 𝑣} ⊆ 𝑒} . 111

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Chapter 4. Some Particular SuperHyperGraphs Definition 4.23.6 (Outerplanar 3-uniform hypergraph (Zykov-type)). Let 𝐻 = (𝑉, E) be 3-uniform (i.e., |𝑒| = 3 for all 𝑒 ∈ E). We say that 𝐻 is outerplanar if 𝜕 (𝐻) has an outerplanar embedding such that, for every hyperedge 𝑒 = {𝑎, 𝑏, 𝑐} ∈ E, the vertices 𝑎, 𝑏, 𝑐 bound an interior triangular face of that embedding. Definition 4.23.7 (𝑛-SuperHyperGraph via iterated super-links). Fix an integer 𝑛 ≥ 1. An 𝑛-superhypergraph is a tuple S = 𝑉, E1 , E2 , . . . , E 𝑛 such that E1 ⊆ P∗ (𝑉) and E𝑖 ⊆ E𝑖−1 2 for every 2 ≤ 𝑖 ≤ 𝑛, where P∗ (𝑋) := P (𝑋) \ {∅}. Elements of E1 are (hyper)edges, and elements of E𝑖 (𝑖 ≥ 2) are called level-𝑖 super-links (links between level-(𝑖 − 1) objects). For 𝑛 = 1 this is exactly a hypergraph (𝑉, E1 ). For 𝑛 = 2 this is exactly a superhypergraph (𝑉, E1 , Λ) with Λ = E2 ⊆ E21 . Definition 4.23.8 (Extended bipartite representation of an 𝑛-superhypergraph). Let S = (𝑉, E1 , . . . , E 𝑛 ) be an 𝑛-superhypergraph. Its extended bipartite representation is the (simple) graph (𝑛) 𝐵ext (S) := 𝑉ext , 𝐹ext , where the vertex set is the tagged (disjoint) union 𝑉ext := 𝑉 ∪¤ E1 ∪¤ E2 ∪¤ · · · ∪¤ E 𝑛 , and the edge set is the union 𝐹ext := 𝐹1 ∪ 𝐹2 ∪ · · · ∪ 𝐹𝑛 , with 𝐹1 := {𝑣, 𝑒} : 𝑣 ∈ 𝑉, 𝑒 ∈ E1 , 𝑣 ∈ 𝑒 , and for every 2 ≤ 𝑖 ≤ 𝑛, 𝐹𝑖 := {𝑥, 𝜆} : 𝜆 ∈ E𝑖 , 𝑥 ∈ E𝑖−1 , 𝑥 ∈ 𝜆 . Definition 4.23.9 (Outerplanar 𝑛-SuperHyperGraph). An 𝑛-superhypergraph S is outerplanar if (𝑛) (S) 𝐵ext is an outerplanar graph. Example 4.23.10 (An outerplanar 2-superhypergraph (outerplanar 𝑛-superhypergraph with 𝑛 = 2)). Let 𝑉 := {1, 2, 3}, E1 := {𝑒 12 , 𝑒 23 }, 𝑒 12 := {1, 2}, 𝑒 23 := {2, 3}. where Define the level-2 super-links by E2 := {𝜆}, 𝜆 := {𝑒 12 , 𝑒 23 } ∈ E1 . 2 Then S := (𝑉, E1 , E2 ) is a 2-superhypergraph. (2) Its extended bipartite representation 𝐵ext (S) = (𝑉ext , 𝐹ext ) has ¤ 12 , 𝑒 23 }∪{𝜆}, ¤ 𝑉ext = 𝑉 ∪¤ E1 ∪¤ E2 = {1, 2, 3}∪{𝑒 and 𝐹ext = 𝐹1 ∪ 𝐹2 , 112

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Chapter 4. Some Particular SuperHyperGraphs where 𝐹1 = {1, 𝑒 12 }, {2, 𝑒 12 }, {2, 𝑒 23 }, {3, 𝑒 23 } , 𝐹2 = {𝑒 12 , 𝜆}, {𝑒 23 , 𝜆} . (2) In 𝐵ext (S) the vertices 2, 𝑒 12 , 𝜆, 𝑒 23 form a 4-cycle 2 − 𝑒 12 − 𝜆 − 𝑒 23 − 2, and the remaining vertices 1 and 3 are leaves attached to 𝑒 12 and 𝑒 23 , respectively. This graph admits an outerplanar embedding by placing the 4-cycle on the boundary of the outer face and attaching the leaves 1 and 3 outside the cycle. Therefore (2) 𝐵ext (S) is outerplanar, and S is an outerplanar 2-superhypergraph (i.e., an outerplanar 𝑛-superhypergraph with 𝑛 = 2). Proposition 4.23.11 (Outerplanar 𝑛-superhypergraphs generalize outerplanar hypergraphs). Let 𝐻 = (𝑉, E) be a hypergraph. Define the associated 𝑛-superhypergraph S𝐻(𝑛) := 𝑉, E1 , E2 , . . . , E 𝑛 by E1 := E and E𝑖 := ∅ (2 ≤ 𝑖 ≤ 𝑛). If 𝐻 is outerplanar (i.e., its incidence graph 𝐵(𝐻) is outerplanar), then S𝐻(𝑛) is an outerplanar 𝑛-superhypergraph. Proof. Let 𝐻 = (𝑉, E) and S𝐻(𝑛) = (𝑉, E1 , . . . , E 𝑛 ) be as defined, so E1 = E and E2 = · · · = E 𝑛 = ∅. (𝑛) By the definition of 𝐵ext (S), we have 𝑉ext = 𝑉 ∪¤ E1 ∪¤ E2 ∪¤ · · · ∪¤ E 𝑛 = 𝑉 ∪¤ E. | {z } =∅ For the edge set, 𝐹ext = 𝐹1 ∪ 𝐹2 ∪ · · · ∪ 𝐹𝑛 . Because E𝑖 = ∅ for every 𝑖 ≥ 2, it follows from 𝐹𝑖 = {𝑥, 𝜆} : 𝜆 ∈ E𝑖 , 𝑥 ∈ E𝑖−1 , 𝑥 ∈ 𝜆 that 𝐹𝑖 = ∅ for all 𝑖 ≥ 2. Hence 𝐹ext = 𝐹1 . But 𝐹1 is exactly the incidence edge set of the usual incidence graph 𝐵(𝐻): 𝐹1 = {𝑣, 𝑒} : 𝑣 ∈ 𝑉, 𝑒 ∈ E, 𝑣 ∈ 𝑒 . Therefore, (𝑛) ¤ 𝐹1 = 𝐵(𝐻). 𝐵ext (S𝐻(𝑛) ) = 𝑉 ∪E, (𝑛) If 𝐻 is outerplanar, then 𝐵(𝐻) is outerplanar by definition, hence 𝐵ext (S𝐻(𝑛) ) is outerplanar, and consequently S𝐻(𝑛) is an outerplanar 𝑛-superhypergraph. □ 4.24 Multimodal Superhypergraphs A Multimodal 𝑛-SuperHyperGraph represents one vertex set with multiple labeled superedge layers, each encoding a distinct interaction modality type assignment [537]. Multimodal Superhypergraphs are known to generalize both multimodal graphs [538–540] and multimodal hypergraphs [541–543]. Moreover, as a related concept, fuzzy multimodal graphs [544, 545] are also well known. The relevant definitions and related notions are presented below. 113

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[beta]

Chapter 4. Some Particular SuperHyperGraphs
Definition 4.24.1 (Multimodal Hypergraph). [541–543] Let 𝑉 be a finite set of vertices and let 𝑀 ∈ N be the
number of modalities. For each modality 𝑚 ∈ {1, 2, . . . , 𝑀 }, let
𝐺 𝑚 = (𝑉, 𝐸 𝑚 , 𝑊𝑚 )
be a (weighted) hypergraph on the common vertex set 𝑉, where:
1. 𝐸 𝑚 is a set of hyperedges, and each hyperedge 𝑒 ∈ 𝐸 𝑚 is a nonempty subset of 𝑉 (typically |𝑒| ≥ 2);
2. 𝑊𝑚 : 𝐸 𝑚 → R>0 assigns a positive weight to each hyperedge 𝑒 ∈ 𝐸 𝑚 .
𝑀 be combination weights satisfying
Let {𝛼𝑚 } 𝑚=1
𝑀
∑︁

𝛼𝑚 ≥ 0 (𝑚 = 1, . . . , 𝑀),

𝛼𝑚 = 1.

𝑚=1

A multimodal hypergraph is the tuple


𝑀
𝑀
𝑀
, {𝛼𝑚 } 𝑚=1
,
, {𝑊𝑚 } 𝑚=1
𝐺 := 𝑉, {𝐸 𝑚 } 𝑚=1
which integrates the modality-specific hypergraphs by weighting each 𝐺 𝑚 by 𝛼𝑚 .
Remark 4.24.2 (Optional combined Laplacian). In applications where each 𝐺 𝑚 induces a Laplacian matrix
𝐿 𝑚 , one often forms a unified operator by the convex combination
𝐿 :=

𝑀
∑︁

𝛼𝑚 𝐿 𝑚 .

𝑚=1

Example 4.24.3 (Real-life multimodal hypergraph: smart-city multimodal commuting analytics). Let a city
analyze commuter groups using multiple data modalities to plan signal timing and public-transport capacity.
Vertex set. Let
𝑉 := {𝑣 1 , . . . , 𝑣 𝑁 }
be a finite set of commuters (or anonymized commuter IDs).
Modalities. Fix 𝑀 = 3 modalities:
𝑚 = 1 : mobile-phone GPS traces,

𝑚 = 2 : transit smart-card taps,

𝑚 = 3 : road-sensor / traffic-counter detections.

For each modality 𝑚 ∈ {1, 2, 3}, define a weighted hypergraph
𝐺 𝑚 = (𝑉, 𝐸 𝑚 , 𝑊𝑚 ),
where each hyperedge groups commuters who jointly exhibit a commuting pattern under that modality.
Hyperedges and weights (concrete meaning).
1. GPS modality 𝑚 = 1. For each weekday time window (e.g., 7:00–9:00) and corridor 𝐶 (a sequence of road
segments), let
𝑒𝐶(1) := { 𝑣 𝑖 ∈ 𝑉 : 𝑣 𝑖 traverses corridor 𝐶 in the window } ∈ 𝐸 1 .
A typical weight is

𝑊1 𝑒𝐶(1) :=

1
𝜀 + Var 𝑇𝐶(1)

,

where 𝑇𝐶(1) is the set of observed travel-times of members of 𝑒𝐶(1) and 𝜀 > 0 is small; thus more consistent
group travel implies larger weight.
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Chapter 4. Some Particular SuperHyperGraphs 2. Transit modality 𝑚 = 2. For a transit line ℓ and time window 𝜏, let (2) 𝑒 ℓ, 𝜏 := { 𝑣 𝑖 ∈ 𝑉 : 𝑣 𝑖 taps-in on line ℓ during 𝜏 } ∈ 𝐸 2 , and define #(co-occurring tap sequences within Δ minutes) (2) , 𝑊2 𝑒 ℓ, 𝜏 := (2) |𝑒 ℓ, 𝜏| so groups with frequent co-occurrence receive higher weight. 3. Road-sensor modality 𝑚 = 3. For an intersection cluster 𝐼 and time window 𝜏, let (3) 𝑒 𝐼, 𝜏 := { 𝑣 𝑖 ∈ 𝑉 : 𝑣 𝑖 is detected near 𝐼 during 𝜏 } ∈ 𝐸 3 , and set (3) 𝑊3 𝑒 𝐼, 𝜏 := average detected flow intensity in (𝐼, 𝜏), so heavily loaded junction-period groups are emphasized. Integration weights. Choose convex combination weights, for example, (𝛼1 , 𝛼2 , 𝛼3 ) = (0.4, 0.4, 0.2), 𝛼𝑚 ≥ 0, 3 ∑︁ 𝛼𝑚 = 1, 𝑚=1 reflecting that GPS and smart-card data are equally trusted, while sensors are noisier. Multimodal hypergraph. The resulting real-life multimodal hypergraph is 𝐺 = 𝑉, {𝐸 𝑚 }3𝑚=1 , {𝑊𝑚 }3𝑚=1 , {𝛼𝑚 }3𝑚=1 , which jointly encodes group commuting relations across GPS, transit, and sensor modalities, and supports downstream tasks such as multimodal clustering of commuting communities or identifying critical multimodal bottlenecks. Definition 4.24.4 (Multimodal 𝑛-SuperHyperGraph). [537] Let SHG (𝑛) = (𝑉, 𝐸) be an 𝑛-SuperHyperGraph and let 𝑀 be a nonempty finite set of modes (or modalities). A Multimodal 𝑛-SuperHyperGraph on SHG (𝑛) is a triple MM-SHG (𝑛) := (𝑉, 𝐸, 𝜆), where 𝜆 : 𝐸 → 𝑀 assigns to each 𝑛-superedge a mode label. For 𝑚 ∈ 𝑀 we set 𝐸 𝑚 := { 𝑒 ∈ 𝐸 | 𝜆(𝑒) = 𝑚 }, so that {𝐸 𝑚 } 𝑚∈ 𝑀 is the family of modal layers of MM-SHG (𝑛) on the common 𝑛-supervertex set 𝑉. Example 4.24.5 (Multimodal 1-SuperHyperGraph: road vs. rail connections). Let the finite base set of atomic districts be 𝑉0 := {North, Center, South}. Then P 1 (𝑉0 ) = P (𝑉0 ) is the collection of all subsets of districts. Define two 1-supervertices 𝑣 1 := {North, Center}, so that 𝑣 1 , 𝑣 2 ∈ P 1 (𝑉0 ) and 𝑣 2 := {Center, South}, 𝑉 := {𝑣 1 , 𝑣 2 } ⊆ P 1 (𝑉0 ). 115

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Chapter 4. Some Particular SuperHyperGraphs Consider the 1-SuperHyperGraph SHG (1) := (𝑉, 𝐸), where the 1-superedge family is 𝐸 := {𝑒 road , 𝑒 rail }, 𝑒 road := {𝑣 1 , 𝑣 2 }, 𝑒 rail := {𝑣 1 , 𝑣 2 }. Both superedges connect the same pair of 1-supervertices but will be distinguished by their mode. Let the set of modes be 𝑀 := {road, rail}, and define 𝜆 : 𝐸 −→ 𝑀, 𝜆(𝑒 road ) := road, 𝜆(𝑒 rail ) := rail. For each 𝑚 ∈ 𝑀 we obtain the modal layers 𝐸 road = {𝑒 road }, 𝐸 rail = {𝑒 rail }. Thus MM-SHG (1) := (𝑉, 𝐸, 𝜆) is a Multimodal 1-SuperHyperGraph. The 1-supervertices represent district pairs (regional clusters), while 𝑒 road and 𝑒 rail encode the same structural connection realized through two distinct modalities: a road corridor and a rail line. 4.25 Lattice Superhypergraphs A lattice is a partially ordered set where any two elements have a unique join (supremum) and meet (infimum) [546, 547]. A Lattice 𝑛-SuperHyperGraph assigns each supervertex and superedge a lattice-valued label, enforcing edge values beneath incident-vertex meets in the lattice [537]. Lattice SuperHyperGraphs are known to generalize lattice hypergraphs [548, 549]. The relevant definitions and related notions are presented below. Definition 4.25.1 (Lattice 𝑛-SuperHyperGraph). [537] Let SHG (𝑛) = (𝑉, 𝐸) be an 𝑛-SuperHyperGraph and let (𝐿, ≤) be a complete lattice with meet ∧. A Lattice 𝑛-SuperHyperGraph on SHG (𝑛) with value lattice 𝐿 is a quintuple Lat-SHG (𝑛) := (𝑉, 𝐸, 𝐿, 𝜎, 𝜇), where • 𝜎 : 𝑉 → 𝐿 assigns to each 𝑛-supervertex 𝑣 ∈ 𝑉 a lattice value 𝜎(𝑣), • 𝜇 : 𝐸 → 𝐿 assigns to each 𝑛-superedge 𝑒 ∈ 𝐸 a lattice value 𝜇(𝑒), subject to the lattice admissibility constraint 𝜇(𝑒) ≤ Û 𝜎(𝑣) for every 𝑒 ∈ 𝐸, 𝑣 ∈𝑒 where the meet Ó 𝑣 ∈𝑒 𝜎(𝑣) is taken in the lattice (𝐿, ≤). Example 4.25.2 (Lattice 2-SuperHyperGraph: discrete risk levels in a hierarchical grid). Let the base set of components be 𝑉0 := {SubstationA, SubstationB, SubstationC}. The first iterated powerset is P1 (𝑉0 ) := P(𝑉0 ), whose elements are ordinary subsets of substations. 116

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Chapter 4. Some Particular SuperHyperGraphs Define the following first-level region subsets (elements of P1 (𝑉0 )): 𝑅 𝐴𝐵 := {SubstationA, SubstationB}, 𝑅 𝐵𝐶 := {SubstationB, SubstationC}, 𝑅all := {SubstationA, SubstationB, SubstationC}. The second iterated powerset is P2 (𝑉0 ) := P P1 (𝑉0 ) , whose elements are sets of such regions. Define two 2-supervertices 𝑣 1 := {𝑅 𝐴𝐵 , 𝑅all }, 𝑣 2 := {𝑅 𝐵𝐶 , 𝑅all }, so that 𝑣 1 , 𝑣 2 ∈ P2 (𝑉0 ). Set 𝑉 := {𝑣 1 , 𝑣 2 } ⊆ P2 (𝑉0 ). Introduce a single 2-superedge 𝑒 grid := {𝑣 1 , 𝑣 2 }, 𝐸 := {𝑒 grid } ⊆ P (𝑉) \ {∅}. Then SHG (2) := (𝑉, 𝐸) is a level-2 SuperHyperGraph over the base set 𝑉0 . Let (𝐿, ≤) be the finite chain 𝐿 := {0, 1, 2}, 0 ≤ 1 ≤ 2, with meet ∧ given by the minimum in this order, interpreted as “low”, “medium”, and “high” risk levels. Define the lattice-valued vertex and edge labels 𝜎 : 𝑉 → 𝐿, 𝜎(𝑣 1 ) := 2, 𝜇 : 𝐸 → 𝐿, 𝜎(𝑣 2 ) := 1, 𝜇(𝑒 grid ) := 1. For the unique 2-superedge 𝑒 grid we check the lattice admissibility constraint 𝜇(𝑒 grid ) ≤ Û 𝜎(𝑣). 𝑣 ∈𝑒grid Indeed, Û 𝜎(𝑣) = 𝜎(𝑣 1 ) ∧ 𝜎(𝑣 2 ) = 2 ∧ 1 = 1, 𝑣 ∈𝑒grid and 𝜇(𝑒 grid ) = 1 ≤ 1 holds. Thus Lat-SHG (2) := (𝑉, 𝐸, 𝐿, 𝜎, 𝜇) is a Lattice 2-SuperHyperGraph. Each 2-supervertex represents a hierarchical cluster of substations (a set of regional groupings), and the 2-superedge 𝑒 grid encodes a joint operational constraint whose lattice-valued risk does not exceed the meet of the incident superclusters’ risk levels. 117

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Chapter 4. Some Particular SuperHyperGraphs 4.26 Hyperbolic Superhypergraphs A Hyperbolic 𝑛-SuperHyperGraph equips its vertex set with a Gromov-hyperbolic graph metric compatible with superedge-induced geodesic paths respecting SuperHyperGraph connectivity [537]. Hyperbolic SuperHypergraphs generalize both hyperbolic graphs [550–552] and hyperbolic hypergraphs [38, 553, 554], extending their geometric behavior to iterated-powerset hierarchies and multi-level relational structures. The relevant definitions and related notions are presented below. Definition 4.26.1 (Hyperbolic 𝑛-SuperHyperGraph). [537] Let SHG (𝑛) = (𝑉, 𝐸) be an 𝑛-SuperHyperGraph. A function 𝑑 : 𝑉 × 𝑉 −→ [0, ∞) is called a graph metric on 𝑉 (for SHG (𝑛) ) if (𝑉, 𝑑) is a metric space and any two vertices of 𝑉 can be joined by a finite 𝑑–geodesic path whose successive vertices are contained in a common 𝑛-superedge of 𝐸. The pair Hyp-SHG (𝑛) := SHG (𝑛) , 𝑑 is called a Hyperbolic 𝑛-SuperHyperGraph if there exists 𝛿 ≥ 0 such that the metric space (𝑉, 𝑑) is 𝛿–hyperbolic in the sense of Gromov (i.e. every geodesic triangle in (𝑉, 𝑑) is 𝛿–thin). Example 4.26.2 (Hyperbolic 2-SuperHyperGraph: tree-shaped hierarchy of router clusters). Let the base set of routers be 𝑉0 := {𝑟 1 , 𝑟 2 , 𝑟 3 , 𝑟 4 }. The first iterated powerset P1 (𝑉0 ) := P(𝑉0 ) contains all subsets of routers. Define the following first-level link groups: 𝐺 12 := {𝑟 1 , 𝑟 2 }, 𝐺 23 := {𝑟 2 , 𝑟 3 }, 𝐺 34 := {𝑟 3 , 𝑟 4 }, all elements of P1 (𝑉0 ). The second iterated powerset P2 (𝑉0 ) := P P1 (𝑉0 ) consists of sets of such link groups. Define three 2-supervertices 𝑣 1 := {𝐺 12 , 𝐺 23 }, 𝑣 2 := {𝐺 23 , 𝐺 34 }, 𝑣 3 := {𝐺 34 }, so that 𝑣 1 , 𝑣 2 , 𝑣 3 ∈ P2 (𝑉0 ). Set 𝑉 := {𝑣 1 , 𝑣 2 , 𝑣 3 } ⊆ P2 (𝑉0 ). Define the 2-superedges 𝑒 12 := {𝑣 1 , 𝑣 2 }, 𝑒 23 := {𝑣 2 , 𝑣 3 }, and put 𝐸 := {𝑒 12 , 𝑒 23 } ⊆ P (𝑉) \ {∅}. Then SHG (2) := (𝑉, 𝐸) is a level-2 SuperHyperGraph whose 2-superedges connect router clusters in a path-like (tree) fashion. Define 𝑑 : 𝑉 × 𝑉 → [0, ∞) to be the usual graph distance on the underlying simple graph with vertex set 𝑉 and edges {𝑣 1 , 𝑣 2 }, {𝑣 2 , 𝑣 3 }. Explicitly, 𝑑 (𝑣 1 , 𝑣 2 ) = 𝑑 (𝑣 2 , 𝑣 3 ) = 1, 𝑑 (𝑣 1 , 𝑣 3 ) = 2, 𝑑 (𝑣 𝑖 , 𝑣 𝑖 ) = 0 for 𝑖 = 1, 2, 3. Then (𝑉, 𝑑) is a tree metric, hence 0-hyperbolic in the sense of Gromov: every geodesic triangle in (𝑉, 𝑑) is 0-thin. Moreover, any 𝑑–geodesic path between two 2-supervertices has successive vertices contained in a common 2-superedge of 𝐸 (for example, the path 𝑣 1 –𝑣 2 –𝑣 3 uses 𝑒 12 and 𝑒 23 ). Therefore Hyp-SHG (2) := SHG (2) , 𝑑 is a Hyperbolic 2-SuperHyperGraph. It models a hierarchical backbone where 2-supervertices are clusters of router-link groups and the tree-shaped connectivity induces a Gromov-hyperbolic graph metric on the space of such clusters. 118

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4.27

Directed Acyclic Superhypergraphs (dash)

A directed acyclic graph is a directed graph containing no directed cycles, admitting a topological ordering
respecting all edges globally [555–557]. Directed acyclic graphs model causal, temporal, and dependency
structures; they enable topological ordering, efficient scheduling and compilation, and underpin Bayesian
networks, workflows, and version-control build systems (cf. [558–560]).
A directed acyclic hypergraph is a directed hypergraph whose hyperedges create no directed cycles, allowing
hierarchical topological ordering constraints overall [561, 562]. A directed acyclic SuperHypergraph is a directed n-SuperHyperGraph without directed superhyperedge cycles, supporting level-wise topological ordering
across all nested structures [563]. The relevant definitions and related notions are presented below.
Definition 4.27.1 (Directed cycle in a directed 𝑛-SuperHyperGraph). [563] Let DSH𝑛 = (𝑉, 𝐸) be a directed
𝑛-SuperHyperGraph. A directed cycle in DSH𝑛 is a sequence of distinct 𝑛-supervertices
𝑣1, 𝑣2, . . . , 𝑣 𝑘 ∈ 𝑉

(𝑘 ≥ 2),

together with directed 𝑛-superhyperedges
𝑒1 , 𝑒2 , . . . , 𝑒 𝑘 ∈ 𝐸
such that for each 𝑖 = 1, . . . , 𝑘 we have
𝑣 𝑖 ∈ 𝑇 (𝑒 𝑖 )

𝑣 𝑖+1 ∈ 𝐻 (𝑒 𝑖 ),

and

where the indices are taken cyclically, i.e. 𝑣 𝑘+1 := 𝑣 1 .
Example 4.27.2 (Directed cycle in a directed 𝑛-SuperHyperGraph). Let
𝑉 := {𝑣 1 , 𝑣 2 , 𝑣 3 }
be a set of three distinct 𝑛-supervertices. Define three directed 𝑛-superhyperedges
𝐸 := {𝑒 1 , 𝑒 2 , 𝑒 3 }
with tail and head sets
𝑇 (𝑒 1 ) := {𝑣 1 },

𝐻 (𝑒 1 ) := {𝑣 2 },

𝑇 (𝑒 2 ) := {𝑣 2 },

𝐻 (𝑒 2 ) := {𝑣 3 },

𝑇 (𝑒 3 ) := {𝑣 3 },

𝐻 (𝑒 3 ) := {𝑣 1 }.

Then
DSH𝑛 := (𝑉, 𝐸)
is a directed 𝑛-SuperHyperGraph.
Consider the sequence of distinct 𝑛-supervertices
𝑣1, 𝑣2, 𝑣3
together with the sequence of directed 𝑛-superhyperedges
𝑒1 , 𝑒2 , 𝑒3 .
We have
𝑣 1 ∈ 𝑇 (𝑒 1 ),

𝑣 2 ∈ 𝐻 (𝑒 1 ),

𝑣 2 ∈ 𝑇 (𝑒 2 ),

𝑣 3 ∈ 𝐻 (𝑒 2 ),

𝑣 3 ∈ 𝑇 (𝑒 3 ),

𝑣 1 ∈ 𝐻 (𝑒 3 ),

and by convention 𝑣 3+1 := 𝑣 1 . Hence 𝑣 1 , 𝑣 2 , 𝑣 3 with 𝑒 1 , 𝑒 2 , 𝑒 3 form a directed cycle in DSH𝑛 in the sense of
Definition 4.27.1.
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Chapter 4. Some Particular SuperHyperGraphs
Definition 4.27.3 (Directed Acyclic SuperHyperGraph (DASH)). A directed 𝑛-SuperHyperGraph
DSH𝑛 = (𝑉, 𝐸)
is called a Directed Acyclic SuperHyperGraph (abbreviated DASH) if it contains no directed cycle in the
sense of Definition 4.27.1; that is, there is no sequence of distinct 𝑛-supervertices 𝑣 1 , . . . , 𝑣 𝑘 and directed
𝑛-superhyperedges 𝑒 1 , . . . , 𝑒 𝑘 ∈ 𝐸 with 𝑘 ≥ 2 such that
𝑣 𝑖 ∈ 𝑇 (𝑒 𝑖 ),

𝑣 𝑖+1 ∈ 𝐻 (𝑒 𝑖 )

(𝑖 = 1, . . . , 𝑘),

𝑣 𝑘+1 := 𝑣 1 .

Equivalently, a directed 𝑛-SuperHyperGraph is a DASH if and only if its supervertices can be arranged in a
topological order compatible with all directed 𝑛-superhyperedges.
Example 4.27.4 (A simple DASH (Directed Acyclic SuperHyperGraph)). Let
𝑉 := {𝑢 1 , 𝑢 2 , 𝑢 3 }
be a set of three distinct 𝑛-supervertices. Define two directed 𝑛-superhyperedges
𝐸 := { 𝑓1 , 𝑓2 }
with tails and heads
𝑇 ( 𝑓1 ) := {𝑢 1 },

𝐻 ( 𝑓1 ) := {𝑢 2 },

𝑇 ( 𝑓2 ) := {𝑢 2 },

𝐻 ( 𝑓2 ) := {𝑢 3 }.

Then
DSH𝑛 := (𝑉, 𝐸)
is a directed 𝑛-SuperHyperGraph.
In this structure, every directed 𝑛-superhyperedge points “forward” from 𝑢 1 to 𝑢 2 and from 𝑢 2 to 𝑢 3 . There is
no sequence of distinct 𝑛-supervertices 𝑣 1 , . . . , 𝑣 𝑘 with 𝑘 ≥ 2 and directed 𝑛-superhyperedges 𝑒 1 , . . . , 𝑒 𝑘 ∈ 𝐸
such that
𝑣 𝑖 ∈ 𝑇 (𝑒 𝑖 ), 𝑣 𝑖+1 ∈ 𝐻 (𝑒 𝑖 ) (𝑖 = 1, . . . , 𝑘),
𝑣 𝑘+1 := 𝑣 1 ,
because there is no way to return from 𝑢 3 back to 𝑢 1 or 𝑢 2 . Thus no directed cycle exists.
Equivalently, the ordering
𝑢1 ≺ 𝑢2 ≺ 𝑢3
is a topological order of the supervertices compatible with all directed 𝑛-superhyperedges, so DSH𝑛 is a
Directed Acyclic SuperHyperGraph (DASH) in the sense of Definition 4.27.3.

4.28

Meta-SuperHyperGraph

A Meta-Graph is a graph whose vertices are graphs, and whose edges represent specified relations between those
graphs [48, 564–566]. Meta-Graph research is important because it models relations between whole graphs,
enabling higher-level reasoning, transfer, compression, and learning across multiple networks, domains, and
scales. A Meta-HyperGraph is a hypergraph whose vertices are hypergraphs, and whose hyperedges group
several hypergraphs whenever a chosen higher-level relation holds [567]. A Meta-SuperHyperGraph is a
hypergraph whose vertices are n-SuperHyperGraphs, and whose hyperedges connect multiple such structures
according to a prescribed multi-way relation [567]. The relevant definitions and related notions are presented
below.
Definition 4.28.1 (MetaGraph (graph of graphs)). [567] Fix a nonempty universe G of finite graphs and
a nonempty family of binary relations R ⊆ P (G × G). A MetaGraph over (G, R) is a directed labelled
multigraph
𝑀 = (𝑉, 𝐸, 𝑠, 𝑡, 𝜆)
such that 𝑉 ⊆ G, 𝑠, 𝑡 : 𝐸 → 𝑉, and 𝜆 : 𝐸 → R, satisfying the incidence constraint
∀𝑒 ∈ 𝐸 : ( 𝑠(𝑒), 𝑡 (𝑒) ) ∈ 𝜆(𝑒).
Vertices are graphs (meta-vertices), and each meta-edge 𝑒 is justified by the relation-label 𝜆(𝑒).
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Chapter 4. Some Particular SuperHyperGraphs Example 4.28.2 (MetaGraph: cross-citing departments). Let G be the class of finite directed acyclic citation graphs (vertices = papers, arcs = citations). Consider the three graphs: 𝐺 CS : 𝑉 = {𝑐 1 , 𝑐 2 , 𝑐 3 }, 𝐸 = {𝑐 2 → 𝑐 1 , 𝑐 3 → 𝑐 2 }, 𝐺 Bio : 𝑉 = {𝑏 1 , 𝑏 2 }, 𝐸 = {𝑏 2 → 𝑏 1 }, 𝐺 Math : 𝑉 = {𝑚 1 , 𝑚 2 }, 𝐸 = {𝑚 2 → 𝑚 1 }. Let the observed cross-department citations be 𝑋 = {𝑐 3 → 𝑏 1 , 𝑐 1 → 𝑚 1 , 𝑏 2 → 𝑐 2 , 𝑚 2 → 𝑐 1 }. For a threshold 𝜏 ∈ N, define a relation 𝑅 𝜏 on G by: (𝐺, 𝐻) ∈ 𝑅 𝜏 ⇐⇒ 𝑐(𝐺, 𝐻) ≥ 𝜏. 𝑐(𝐺, 𝐻) := {( 𝑝, 𝑞) ∈ 𝑉 (𝐺) × 𝑉 (𝐻) : 𝑝 → 𝑞 ∈ 𝑋 } , With 𝜏 = 1, we have 𝑐(𝐺 CS , 𝐺 Bio ) = 1, 𝑐(𝐺 CS , 𝐺 Math ) = 1, 𝑐(𝐺 Bio , 𝐺 CS ) = 1, 𝑐(𝐺 Math , 𝐺 CS ) = 1, and all other cross-counts are 0. Hence the MetaGraph over (G, {𝑅1 }) can be taken as 𝑉 = {𝐺 CS , 𝐺 Bio , 𝐺 Math }, 𝐸 = {𝑒 1 , 𝑒 2 , 𝑒 3 , 𝑒 4 }, 𝜆(𝑒 𝑖 ) = 𝑅1 (𝑖 = 1, 2, 3, 4), with sources/targets 𝑠(𝑒 1 ) = 𝐺 CS , 𝑡 (𝑒 1 ) = 𝐺 Bio , 𝑠(𝑒 2 ) = 𝐺 CS , 𝑡 (𝑒 2 ) = 𝐺 Math , 𝑠(𝑒 3 ) = 𝐺 Bio , 𝑡 (𝑒 3 ) = 𝐺 CS , 𝑠(𝑒 4 ) = 𝐺 Math , 𝑡 (𝑒 4 ) = 𝐺 CS . Each incidence condition (𝑠(𝑒 𝑖 ), 𝑡 (𝑒 𝑖 )) ∈ 𝑅1 holds by the computed counts. Definition 4.28.3 (MetaHyperGraph (HyperGraph of HyperGraphs)). [567] Let 𝑈 be a nonempty universe of objects and let R ⊆ P Pfin (𝑈) × Pfin (𝑈) be a nonempty family of admissible set-relations. A MetaHyperGraph over (𝑈, R) is a labelled directed hypergraph 𝑀 = (𝑉, 𝐸, 𝑇, 𝐻𝑑, 𝜆) with 𝑉 ⊆ 𝑈, tail/head maps 𝑇, 𝐻𝑑 : 𝐸 → Pfin (𝑉), and label map 𝜆 : 𝐸 → R, such that ∀𝑒 ∈ 𝐸 : 𝑇 (𝑒), 𝐻𝑑 (𝑒) ∈ 𝜆(𝑒). If 𝑈 is chosen as the class of finite hypergraphs, then 𝑀 is literally a “hypergraph whose vertices are hypergraphs.” Example 4.28.4 (MetaHyperGraph: hospital departments sharing patients). Let each meta-vertex be a finite (undirected) hypergraph whose vertices are patient IDs and whose hyperedges are procedure sessions. Consider three departmental hypergraphs: 𝐻Rad : 𝑉 = {𝑝 1 , 𝑝 2 , 𝑝 3 }, 𝐸 = {𝑝 1 , 𝑝 2 }, {𝑝 2 , 𝑝 3 } , 𝐻Card : 𝑉 = {𝑝 2 , 𝑝 4 }, 𝐸 = {𝑝 2 }, {𝑝 2 , 𝑝 4 } , 𝐻Onc : 𝑉 = {𝑝 1 , 𝑝 2 , 𝑝 5 }, 𝐸 = {𝑝 1 , 𝑝 2 }, {𝑝 2 , 𝑝 5 } . Define a set-relation 𝑅share on finite families of departmental hypergraphs by: (𝑆, 𝑇) ∈ 𝑅share ⇐⇒ ∃𝑥 (patient ID) such that ∀𝐻 ∈ 𝑆 ∪ 𝑇, ∃𝑒 ∈ 𝐸 (𝐻) with 𝑥 ∈ 𝑒. Form a MetaHyperGraph 𝑀 = (𝑉, 𝐸, 𝑇, 𝐻𝑑, 𝜆) over ({𝐻Rad , 𝐻Card , 𝐻Onc }, {𝑅share }) by 𝑉 = {𝐻Rad , 𝐻Card , 𝐻Onc }, 𝐸 = {𝑒 1 }, 𝑇 (𝑒 1 ) = {𝐻Rad , 𝐻Card }, 𝐻𝑑 (𝑒 1 ) = {𝐻Onc }, 𝜆(𝑒 1 ) = 𝑅share . 𝑝 2 ∈ {𝑝 2 } ∈ 𝐸 (𝐻Card ), 𝑝 2 ∈ {𝑝 1 , 𝑝 2 } ∈ 𝐸 (𝐻Onc ), Incidence check: choose 𝑥 = 𝑝 2 . Then 𝑝 2 ∈ {𝑝 1 , 𝑝 2 } ∈ 𝐸 (𝐻Rad ), so 𝑇 (𝑒 1 ), 𝐻𝑑 (𝑒 1 ) ∈ 𝑅share = 𝜆(𝑒 1 ). 121

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Chapter 4. Some Particular SuperHyperGraphs Definition 4.28.5 (MetaSuperHyperGraph (SuperHyperGraph of SuperHyperGraphs)). [567] Fix 𝑛 ∈ N0 and let S𝑛 denote the class of all finite directed 𝑛-SuperHyperGraphs (over arbitrary base sets). Let R ⊆ P Pfin (S𝑛 ) × Pfin (S𝑛 ) be a nonempty family of admissible set-relations on 𝑛-SuperHyperGraphs. A MetaSuperHyperGraph over (S𝑛 , R) is a labelled directed hypergraph 𝑀 = (𝑉, 𝐸, 𝑇, 𝐻𝑑, 𝜆) such that 𝑉 ⊆ S𝑛 , 𝑇, 𝐻𝑑 : 𝐸 → Pfin (𝑉), 𝜆 : 𝐸 → R, and ∀𝑒 ∈ 𝐸 : 𝑇 (𝑒), 𝐻𝑑 (𝑒) ∈ 𝜆(𝑒). Example 4.28.6 (MetaSuperHyperGraph: multi-department clinical cohorts (depth 𝑛 = 1)). Let the patient-ID universe be Ω = {𝑢 1 , 𝑢 2 , 𝑢 3 , 𝑢 4 , 𝑢 5 } and consider depth-1 SuperHyperGraphs (so their vertices are subsets of Ω). Define three 1-SuperHyperGraphs: Department A (oncology): 𝐻 𝐴 = (𝑉 𝐴, 𝐸 𝐴, 𝑇𝐴, 𝐻𝑑 𝐴), 𝑉 𝐴 = {𝑢 1 , 𝑢 2 }, {𝑢 2 , 𝑢 3 } , 𝐸 𝐴 = {𝑒 𝐴 }, 𝑇𝐴 (𝑒 𝐴) = {𝑢 1 , 𝑢 2 } , 𝐻𝑑 𝐴 (𝑒 𝐴) = {𝑢 2 , 𝑢 3 } . Department B (radiology): 𝐻 𝐵 = (𝑉𝐵 , 𝐸 𝐵 , 𝑇𝐵 , 𝐻𝑑 𝐵 ), 𝑉𝐵 = {𝑢 2 , 𝑢 4 } , 𝐸 𝐵 = ∅. Department C (cardiology): 𝐻𝐶 = (𝑉𝐶 , 𝐸𝐶 , 𝑇𝐶 , 𝐻𝑑𝐶 ), 𝑉𝐶 = {𝑢 1 , 𝑢 2 , 𝑢 5 } , 𝐸𝐶 = ∅. Define a set-relation 𝑅share𝑉 on finite families of 1-SuperHyperGraphs by (𝑆, 𝑇) ∈ 𝑅share𝑉 ⇐⇒ ∃𝑥 ∈ Ω such that ∀𝐻 ∈ 𝑆 ∪ 𝑇, ∃𝐴 𝐻 ∈ 𝑉 (𝐻) with 𝑥 ∈ 𝐴 𝐻 . Now form a MetaSuperHyperGraph 𝑀 = (𝑉, 𝐸, 𝑇, 𝐻𝑑, 𝜆) over ({𝐻 𝐴, 𝐻 𝐵 , 𝐻𝐶 }, {𝑅share𝑉 }) by 𝑉 = {𝐻 𝐴, 𝐻 𝐵 , 𝐻𝐶 }, 𝐸 = {𝑒★ }, 𝑇 (𝑒★) = {𝐻 𝐴, 𝐻 𝐵 }, 𝐻𝑑 (𝑒★) = {𝐻𝐶 }, 𝜆(𝑒★) = 𝑅share𝑉 . Incidence check: pick 𝑥 = 𝑢 2 . Then 𝑢 2 ∈ {𝑢 1 , 𝑢 2 } ∈ 𝑉 𝐴, so 𝑇 (𝑒★), 𝐻𝑑 (𝑒★) ∈ 𝑅share𝑉 = 𝜆(𝑒★). 𝑢 2 ∈ {𝑢 2 , 𝑢 4 } ∈ 𝑉𝐵 , 𝑢 2 ∈ {𝑢 1 , 𝑢 2 , 𝑢 5 } ∈ 𝑉𝐶 , An overview of Meta-Graph, Meta-HyperGraph, and Meta-SuperHyperGraph is presented in Table 4.14. 4.29 Regular SuperHyperGraph A regular graph has each vertex incident to exactly 𝑘 edges, so all vertices share the same degree [444, 568]. Related concepts include regular fuzzy graphs [569, 570], irregular graphs [571–573], regular intuitionistic fuzzy graphs [574, 575], strongly regular graphs [576, 577], edge-regular graphs [578–580], regular neutrosophic graphs [581–583], as well as biregular [584, 585] and triregular graphs [586]. Regular graph research is important because uniform degrees yield clean theory, sharp extremal bounds, efficient algorithms, and realistic models for symmetric networks, designs, codes, and expanders. The relevant definitions and related notions are presented below. A regular hypergraph has each vertex contained in exactly 𝑟 hyperedges, so every vertex has the same hyperedgedegree [587–589]. A regular SuperHyperGraph has each supervertex incident with exactly 𝑟 superedges via 𝜕, so all supervertices have identical degree. 122

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Chapter 4. Some Particular SuperHyperGraphs Object Meta-Graph Meta-vertices Graphs Meta-HyperGraph HyperGraphs MetaSuperHyperGraph 𝑛-SuperHyperGraphs Meta-edges / hyperedges (relation layer) Edges encode a chosen binary relation between graphs (e.g., “shares a motif”, “cites”, “is similar”). Hyperedges group multiple hypergraphs when a multi-way relation holds (e.g., “share a common vertex-set pattern”). Hyperedges connect several 𝑛SuperHyperGraphs according to a prescribed multi-way relation on super-level objects. Table 4.14: Concise overview of Meta-Graph, Meta-HyperGraph, and Meta-SuperHyperGraph. Definition 4.29.1 (Regular graph). [590] Let 𝐺 = (𝑉 (𝐺), 𝐸 (𝐺)) be a finite undirected loopless graph, where 𝐸 (𝐺) ⊆ {𝑢, 𝑣} | 𝑢, 𝑣 ∈ 𝑉 (𝐺), 𝑢 ≠ 𝑣 . For 𝑣 ∈ 𝑉 (𝐺), the (vertex) degree of 𝑣 is deg𝐺 (𝑣) := { 𝑒 ∈ 𝐸 (𝐺) | 𝑣 ∈ 𝑒 } . For an integer 𝑘 ∈ N0 , the graph 𝐺 is called 𝑘-regular if deg𝐺 (𝑣) = 𝑘 (∀ 𝑣 ∈ 𝑉 (𝐺)). Definition 4.29.2 (Regular hypergraph). [587–589] Let 𝐻 = (𝑉 (𝐻), 𝐸 (𝐻)) be a finite hypergraph, where 𝑉 (𝐻) ≠ ∅, 𝐸 (𝐻) ⊆ P∗ 𝑉 (𝐻) := P 𝑉 (𝐻) \ {∅}. For 𝑣 ∈ 𝑉 (𝐻), the (vertex) degree of 𝑣 is deg 𝐻 (𝑣) := { 𝑒 ∈ 𝐸 (𝐻) | 𝑣 ∈ 𝑒 } . For an integer 𝑟 ∈ N0 , the hypergraph 𝐻 is called 𝑟-regular if deg 𝐻 (𝑣) = 𝑟 (∀ 𝑣 ∈ 𝑉 (𝐻)). Example 4.29.3 (A 2-regular hypergraph). Let 𝑉 (𝐻) := {1, 2, 3}, 𝐸 (𝐻) := 𝑒 12 , 𝑒 23 , 𝑒 31 , where 𝑒 12 := {1, 2}, 𝑒 23 := {2, 3}, 𝑒 31 := {3, 1}. For each vertex 𝑣 ∈ 𝑉 (𝐻), deg 𝐻 (𝑣) = { 𝑒 ∈ 𝐸 (𝐻) | 𝑣 ∈ 𝑒 } . Hence deg 𝐻 (1) = |{𝑒 12 , 𝑒 31 }| = 2, deg 𝐻 (2) = |{𝑒 12 , 𝑒 23 }| = 2, deg 𝐻 (3) = |{𝑒 23 , 𝑒 31 }| = 2. Therefore 𝐻 is 2-regular. Definition 4.29.4 (Regular 𝑛-SuperHyperGraph). Let 𝑛 ∈ N0 and let SHG (𝑛) = (𝑉, 𝐸, 𝜕) be an 𝑛-SuperHyperGraph, where 𝑉 ⊆ P 𝑛 (𝑉0 ) is finite, 𝐸 is finite, and 𝜕 : 𝐸 → P∗ (𝑉) is the incidence map. For a supervertex 𝑣 ∈ 𝑉, define its (vertex) degree by degSHG (𝑣) := { 𝑒 ∈ 𝐸 | 𝑣 ∈ 𝜕 (𝑒) } . For an integer 𝑟 ∈ N0 , the 𝑛-SuperHyperGraph SHG (𝑛) is called 𝑟-regular if degSHG (𝑣) = 𝑟 123 (∀ 𝑣 ∈ 𝑉).

#p286

125.

Chapter 4. Some Particular SuperHyperGraphs Example 4.29.5 (A 2-regular 2-SuperHyperGraph). Fix the base set 𝑉0 := {𝑎, 𝑏, 𝑐}. Define 2-supervertices (note 𝑉 ⊆ P 2 (𝑉0 ) = P (P (𝑉0 ))) by 𝑉 := {𝑣 𝑎 , 𝑣 𝑏 , 𝑣 𝑐 }, 𝑣 𝑎 := {{𝑎}}, 𝑣 𝑏 := {{𝑏}}, 𝑣 𝑐 := {{𝑐}}. Let 𝐸 := {𝑒 𝑎𝑏 , 𝑒 𝑏𝑐 , 𝑒 𝑐𝑎 }, 𝑒 𝑎𝑏 := {𝑣 𝑎 , 𝑣 𝑏 }, 𝑒 𝑏𝑐 := {𝑣 𝑏 , 𝑣 𝑐 }, 𝑒 𝑐𝑎 := {𝑣 𝑐 , 𝑣 𝑎 }, and define the incidence map 𝜕 : 𝐸 → P∗ (𝑉), 𝜕 (𝑒) := 𝑒 (𝑒 ∈ 𝐸). For each supervertex 𝑣 ∈ 𝑉, define degSHG (𝑣) = { 𝑒 ∈ 𝐸 | 𝑣 ∈ 𝜕 (𝑒) } . Then degSHG (𝑣 𝑎 ) = |{𝑒 𝑎𝑏 , 𝑒 𝑐𝑎 }| = 2, degSHG (𝑣 𝑏 ) = |{𝑒 𝑎𝑏 , 𝑒 𝑏𝑐 }| = 2, degSHG (𝑣 𝑐 ) = |{𝑒 𝑏𝑐 , 𝑒 𝑐𝑎 }| = 2. Therefore SHG (2) = (𝑉, 𝐸, 𝜕) is a 2-regular 2-SuperHyperGraph. Theorem 4.29.6 (Regular SuperHyperGraphs generalize regular hypergraphs). For every finite 𝑟-regular hypergraph 𝐻 = (𝑉 (𝐻), 𝐸 (𝐻)), there exists a finite 𝑟-regular 0-SuperHyperGraph SHG (0) = (𝑉, 𝐸, 𝜕) whose incidence structure is identical to that of 𝐻 (hence 𝐻 is recovered from SHG (0) by forgetting the superscript 0). Equivalently, the class of 𝑟-regular hypergraphs embeds into the class of 𝑟-regular SuperHyperGraphs (already at level 𝑛 = 0). Proof. Let 𝐻 = (𝑉 (𝐻), 𝐸 (𝐻)) be a finite 𝑟-regular hypergraph. Thus 𝐸 (𝐻) ⊆ P∗ (𝑉 (𝐻)) deg 𝐻 (𝑣) = 𝑟 (∀ 𝑣 ∈ 𝑉 (𝐻)), and where deg 𝐻 (𝑣) = { 𝑒 ∈ 𝐸 (𝐻) | 𝑣 ∈ 𝑒 } . We construct a 0-SuperHyperGraph SHG (0) that preserves degrees. Step 1: Choose base set and level. Set 𝑉0 := 𝑉 (𝐻), 𝑛 := 0. Then P 0 (𝑉0 ) = 𝑉0 . Step 2: Define supervertices. Let 𝑉 := 𝑉0 = 𝑉 (𝐻). Hence 𝑉 ⊆ P 0 (𝑉0 ) holds. Step 3: Define superedges and incidence map. Let 𝐸 := 𝐸 (𝐻), 𝜕 : 𝐸 → P∗ (𝑉) by 𝜕 (𝑒) := 𝑒 (∀ 𝑒 ∈ 𝐸). This is well-defined because each 𝑒 ∈ 𝐸 (𝐻) is a nonempty subset of 𝑉 (𝐻) = 𝑉, so 𝜕 (𝑒) = 𝑒 ∈ P∗ (𝑉). Therefore SHG (0) := (𝑉, 𝐸, 𝜕) 124

126.

[beta]

Chapter 4. Some Particular SuperHyperGraphs
is a valid 0-SuperHyperGraph.
Step 4: Verify preservation of regularity (degree equality). Fix any 𝑣 ∈ 𝑉 = 𝑉 (𝐻). By definition of degSHG
and 𝜕 (𝑒) = 𝑒,
degSHG (𝑣) = { 𝑒 ∈ 𝐸 | 𝑣 ∈ 𝜕 (𝑒) } = { 𝑒 ∈ 𝐸 (𝐻) | 𝑣 ∈ 𝑒 } = deg 𝐻 (𝑣).
Since 𝐻 is 𝑟-regular, deg 𝐻 (𝑣) = 𝑟 for all 𝑣 ∈ 𝑉 (𝐻), hence
degSHG (𝑣) = 𝑟
Thus SHG

(0)

(∀ 𝑣 ∈ 𝑉).

is 𝑟-regular.

Finally, the incidence relation in 𝐻 is “𝑣 ∈ 𝑒”, while in SHG (0) it is “𝑣 ∈ 𝜕 (𝑒)”; but 𝜕 (𝑒) = 𝑒, so these coincide.
Hence 𝐻 is recovered exactly from SHG (0) , and regular hypergraphs are included as special cases of regular
SuperHyperGraphs (level 0).
□

4.30

Intersection SuperHyperGraph

Intersection graph represents sets as vertices and connects two vertices exactly when the corresponding sets
share at least one element [591–595]. As related concepts to intersection graphs, Fuzzy Intersection Graphs
[596, 597], Neutrosophic Intersection Graphs [598], and Intersection Directed Graphs [599–601] are also
known. In addition, Appendix A provides an overview of Multi-Intersection Graphs. Intersection graph
research is important because it models overlap constraints in geometry and systems, enabling structural
theorems, recognition algorithms, complexity insights, and applications in scheduling and VLSI (cf. [602,603]).
Intersection hypergraph represents sets as vertices and assigns each hyperedge from a witness set 𝐵, collecting
all vertices whose sets intersect 𝐵 [604–606]. Intersection superhypergraph represents sets as supervertices and
uses a superhyperedge for any subfamily with nonempty common intersection, capturing higher-order overlaps.
The relevant definitions and related notions are presented below.
Definition 4.30.1 (Intersection graph). [607] Let 𝑋 be a set and let S = {𝑆1 , . . . , 𝑆 𝑚 } ⊆ P (𝑋) \ {∅}. The
intersection graph of S is the (simple, undirected) graph
IG(S) = (𝑉, 𝐸),

𝑉 := {1, . . . , 𝑚},

{𝑖, 𝑗 } ∈ 𝐸 ⇐⇒ 𝑖 ≠ 𝑗 and 𝑆𝑖 ∩ 𝑆 𝑗 ≠ ∅.

Equivalently, one may take 𝑉 := S and join 𝑆𝑖 , 𝑆 𝑗 iff 𝑆𝑖 ∩ 𝑆 𝑗 ≠ ∅.
Definition 4.30.2 (Intersection hypergraph (with respect to a second family)). [608] Let 𝑋 be a set and let
A = {𝐴1 , . . . , 𝐴𝑚 } ⊆ P (𝑋) \ {∅},

B = {𝐵1 , . . . , 𝐵𝑟 } ⊆ P (𝑋) \ {∅}.

The intersection hypergraph of A with respect to B is the hypergraph
IH(A | B) = (𝑉, E),

𝑉 := {1, . . . , 𝑚},

E := {𝑒 1 , . . . , 𝑒𝑟 },

where, for each 𝑗 ∈ {1, . . . , 𝑟 },
𝑒 𝑗 := { 𝑖 ∈ 𝑉 : 𝐴𝑖 ∩ 𝐵 𝑗 ≠ ∅ }.
If one wants a simple hypergraph, discard hyperedges of size ≤ 1 and remove duplicates.
Example 4.30.3 (Intersection hypergraph IH(A | B)). Let 𝑋 := {1, 2, 3, 4} and
A = {𝐴1 , 𝐴2 , 𝐴3 } ⊆ P (𝑋) \ {∅},

𝐴1 = {1, 2}, 𝐴2 = {2, 3}, 𝐴3 = {4},

B = {𝐵1 , 𝐵2 , 𝐵3 } ⊆ P (𝑋) \ {∅},

𝐵1 = {2}, 𝐵2 = {3, 4}, 𝐵3 = {1, 4}.

Then 𝑉 = {1, 2, 3} and the hyperedges are
𝑒 1 = { 𝑖 ∈ 𝑉 : 𝐴𝑖 ∩ 𝐵1 ≠ ∅ } = {1, 2},
𝑒 2 = { 𝑖 ∈ 𝑉 : 𝐴𝑖 ∩ 𝐵2 ≠ ∅ } = {2, 3},
𝑒 3 = { 𝑖 ∈ 𝑉 : 𝐴𝑖 ∩ 𝐵3 ≠ ∅ } = {1, 3}.
Hence
IH(A | B) = ({1, 2, 3}, { {1, 2}, {2, 3}, {1, 3} }).
In particular, each 𝑒 𝑗 collects exactly those 𝐴𝑖 that intersect the witness set 𝐵 𝑗 .
125

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Chapter 4. Some Particular SuperHyperGraphs Definition 4.30.4 (Intersection 𝑛-superhypergraph (common-intersection superhyperedges)). Fix an integer 𝑛 ≥ 1. Let 𝑋 be a set and let S = {𝑆1 , . . . , 𝑆 𝑚 } ⊆ P (𝑋) \ {∅}. Define the ground set 𝑉𝑋 := 𝑚 Ø 𝑆𝑖 , 𝑖=1 and define the supervertex family (level-1 vertices) by V := {𝑆1 , . . . , 𝑆 𝑚 } ⊆ P (𝑉𝑋 ) \ {∅}. For each 𝑇 ⊆ V with |𝑇 | ≥ 2, define the associated level-𝑛 superhyperedge by 𝑒𝑇(𝑛) := 𝑇b (𝑛−1) ∈ P 𝑛 (V), where the liftingb· (𝑛−1) is defined recursively by b (0) := 𝐴, 𝐴 (𝑡 ) b (𝑡+1) := b 𝐴 𝑎 :𝑎∈𝐴 (𝑡 ≥ 0), and, for an individual element 𝑎, we set b 𝑎 (0) := 𝑎 and b 𝑎 (𝑡+1) := {b 𝑎 (𝑡 ) }. The intersection 𝑛-superhypergraph of S is the set-based 𝑛-superhypergraph ISH (𝑛) (S) := 𝑉𝑋 , V, SE (𝑛) , whose level-𝑛 superhyperedge family SE (𝑛) ⊆ P 𝑛 (V) is n o Ù SE (𝑛) := 𝑒𝑇(𝑛) 𝑇 ⊆ V, |𝑇 | ≥ 2, 𝑈≠∅ . 𝑈 ∈𝑇 Thus a level-𝑛 superhyperedge is (the (𝑛−1)-fold lift of) a subfamily of S having a nonempty common intersection. Example 4.30.5 (Intersection 𝑛-superhypergraph ISH (𝑛) (S)). Let 𝑋 := {1, 2, 3, 4} and S = {𝑆1 , 𝑆2 , 𝑆3 , 𝑆4 } ⊆ P (𝑋) \ {∅}, 𝑆1 = {1, 2}, 𝑆2 = {2, 3}, 𝑆3 = {2, 4}, 𝑆4 = {3, 4}. Ð4 Then 𝑉𝑋 = 𝑖=1 𝑆𝑖 = 𝑋 and V = {𝑆1 , 𝑆2 , 𝑆3 , 𝑆4 }. (𝑛) b (𝑛−1) ∈ P 𝑛 (V) if and only if A Ñ subset 𝑇 ⊆ V with |𝑇 | ≥ 2 yields a level-𝑛 superhyperedge 𝑒𝑇 = 𝑇 𝑈 ∈𝑇 𝑈 ≠ ∅. Pairwise intersections: 𝑆1 ∩ 𝑆2 = {2} ≠ ∅, 𝑆2 ∩ 𝑆3 = {2} ≠ ∅, 𝑆1 ∩ 𝑆3 = {2} ≠ ∅, 𝑆2 ∩ 𝑆4 = {3} ≠ ∅, 𝑆1 ∩ 𝑆4 = ∅, 𝑆3 ∩ 𝑆4 = {4} ≠ ∅. Hence the level-𝑛 superhyperedges coming from 2-subfamilies are exactly (𝑛) (𝑛) (𝑛) (𝑛) (𝑛) 𝑒 {𝑆 , 𝑒 {𝑆 , 𝑒 {𝑆 , 𝑒 {𝑆 , 𝑒 {𝑆 . ,𝑆 } ,𝑆 } ,𝑆 } ,𝑆 } ,𝑆 } 1 2 1 3 2 3 2 4 A genuine higher-order overlap occurs for the triple: 𝑆1 ∩ 𝑆2 ∩ 𝑆3 = {2} ≠ ∅, so the corresponding level-𝑛 superhyperedge (𝑛−1) (𝑛) 𝑒 {𝑆 = {𝑆 1 , 𝑆2 , 𝑆3 } ,𝑆 ,𝑆 } 1 2 3 belongs to SE (𝑛) . 126 3 4

128.

Chapter 4. Some Particular SuperHyperGraphs But 𝑆1 ∩ 𝑆2 ∩ 𝑆4 = ∅, 𝑆1 ∩ 𝑆3 ∩ 𝑆4 = ∅, 𝑆2 ∩ 𝑆3 ∩ 𝑆4 = ∅, and also 𝑆1 ∩ 𝑆2 ∩ 𝑆3 ∩ 𝑆4 = ∅. Therefore, in this example, n o (𝑛) (𝑛) (𝑛) (𝑛) (𝑛) (𝑛) SE (𝑛) = 𝑒 {𝑆 , 𝑒 , 𝑒 , 𝑒 , 𝑒 , 𝑒 . ,𝑆 } {𝑆 ,𝑆 } {𝑆 ,𝑆 } {𝑆 ,𝑆 } {𝑆 ,𝑆 } {𝑆 ,𝑆 ,𝑆 } 1 2 1 3 2 3 2 4 3 4 1 2 3 This shows that ISH (𝑛) (S) records not only pairwise intersections, but also common intersections of larger subfamilies, lifted to level 𝑛. 4.31 Bipartite SuperHyperGraph A bipartite graph is a graph whose vertices split into two disjoint parts, and every edge has endpoints in different parts only [609–611]. As related concepts, bipartite fuzzy graphs [612], bipartite neutrosophic graphs [613, 614], tripartite graphs [615–617], nearly bipartite graphs [618], bipartable graphs [619], and bipartite directed graphs [620, 621] are well known. In addition, as graph classes formed by bipartite + an additional property, several families are known, including bipartite tolerance graphs [622,623], circular convex bipartite graphs [624, 625], chordal bipartite graphs [626, 627], and bipartite permutation graphs [628, 629]. Bipartite graphs admit efficient matchings and colorings, model two-type relations naturally, and avoid odd cycles, simplifying many algorithms. A bipartite hypergraph is a hypergraph with a vertex partition 𝐴 ⊔ 𝐵 such that each hyperedge intersects both parts, 𝑒 ∩ 𝐴 ≠ ∅ and 𝑒 ∩ 𝐵 ≠ ∅ [630–632]. A bipartite superhypergraph is a superhypergraph with a supervertex partition V1 ⊔ V2 such that every superhyperedge meets both parts nontrivially. The relevant definitions and related notions are presented below. Definition 4.31.1 (Bipartite Graph). [609–611] A graph is a pair 𝐺 = (𝑉, 𝐸) where 𝑉 is a (finite) set and 𝐸 ⊆ {𝑢, 𝑣} ⊆ 𝑉 : 𝑢 ≠ 𝑣 . The graph 𝐺 is bipartite if there exist disjoint sets 𝑉1 , 𝑉2 ⊆ 𝑉 such that 𝑉 = 𝑉1 ⊔ 𝑉2 and ∀ {𝑢, 𝑣} ∈ 𝐸 : 𝑢 ∈ 𝑉1 & 𝑣 ∈ 𝑉2 or 𝑢 ∈ 𝑉2 & 𝑣 ∈ 𝑉1 . Equivalently, no edge has both endpoints in the same part. Definition 4.31.2 (Bipartite Hypergraph). [630–632] A hypergraph is a pair 𝐻 = (𝑉, E) where 𝑉 is a (finite) set and E ⊆ P (𝑉) \ {∅} is a family of nonempty subsets of 𝑉 (hyperedges). The hypergraph 𝐻 is bipartite if there exist disjoint sets 𝐴, 𝐵 ⊆ 𝑉 such that 𝑉 = 𝐴⊔𝐵 and ∀ 𝑒 ∈ E : 𝑒 ∩ 𝐴 ≠ ∅ and 𝑒 ∩ 𝐵 ≠ ∅. (In particular, no hyperedge is contained entirely in one part.) Example 4.31.3 (Bipartite hypergraph). Let 𝑉 := {𝑎, 𝑏, 𝑐, 𝑑, 𝑒}, 𝐴 := {𝑎, 𝑏}, 𝐵 := {𝑐, 𝑑, 𝑒}, 𝑉 = 𝐴 ⊔ 𝐵. Define the hyperedge family E := {𝑒 1 , 𝑒 2 , 𝑒 3 }, 𝑒 1 := {𝑎, 𝑐}, 𝑒 2 := {𝑏, 𝑑, 𝑒}, 𝑒 3 := {𝑎, 𝑏, 𝑐, 𝑑}. Then each hyperedge meets both parts: 𝑒 1 ∩ 𝐴 = {𝑎} ≠ ∅, 𝑒 1 ∩ 𝐵 = {𝑐} ≠ ∅, 𝑒 2 ∩ 𝐴 = {𝑏} ≠ ∅, 𝑒 2 ∩ 𝐵 = {𝑑, 𝑒} ≠ ∅, 𝑒 3 ∩ 𝐴 = {𝑎, 𝑏} ≠ ∅, 𝑒 3 ∩ 𝐵 = {𝑐, 𝑑} ≠ ∅. Hence 𝐻 := (𝑉, E) is a bipartite hypergraph with bipartition ( 𝐴, 𝐵). 127

#p287

129.

Chapter 4. Some Particular SuperHyperGraphs Definition 4.31.4 (Bipartite 𝑛-superhypergraph). Fix an integer 𝑛 ≥ 1. An 𝑛-superhypergraph is a pair SHG (𝑛) = (V, F (𝑛) ) where V is a nonempty set (of supervertices) and F (𝑛) ⊆ P 𝑛 (V) \ {∅} is a family of level-𝑛 superhyperedges. We say that SHG (𝑛) is bipartite if there exist disjoint sets V1 , V2 ⊆ V such that V = V1 ⊔ V2 and ∀ 𝐹 ∈ F (𝑛) : Flat(𝐹) ∩ V1 ≠ ∅ and Flat(𝐹) ∩ V2 ≠ ∅, where Flat(𝐹) ⊆ V denotes the vertex-level flattening of 𝐹, defined recursively by Ø Flat0 (𝑈) := 𝑈 (𝑈 ⊆ V), Flat𝑡+1 ( 𝐴) := Flat𝑡 (𝑥), 𝑥∈ 𝐴 and Flat(𝐹) := Flat𝑛 (𝐹) for 𝐹 ∈ P 𝑛 (V). Thus each level-𝑛 superhyperedge, when flattened down to the vertex level, meets both sides of the bipartition. Example 4.31.5 (Bipartite 𝑛-superhypergraph). Fix 𝑛 ≥ 1 and let V := {𝑈1 , 𝑈2 , 𝑈3 , 𝑈4 , 𝑈5 }, V1 := {𝑈1 , 𝑈2 }, V2 := {𝑈3 , 𝑈4 , 𝑈5 }, V = V1 ⊔ V2 . Define three vertex-level supports 𝑇1 := {𝑈1 , 𝑈3 }, 𝑇2 := {𝑈2 , 𝑈4 , 𝑈5 }, 𝑇3 := {𝑈1 , 𝑈2 , 𝑈4 }. Lift each 𝑇𝑖 to a level-𝑛 superhyperedge by (𝑛−1) 𝐹𝑖(𝑛) := 𝑇b𝑖 ∈ P 𝑛 (V), whereb· (𝑛−1) is the (𝑛−1)-fold singleton-lift: b (0) := 𝐴, 𝐴 b (𝑡+1) := {b 𝐴 𝑎 (𝑡 ) : 𝑎 ∈ 𝐴} (𝑡 ≥ 0), and for 𝑎 ∈ V we set b 𝑎 (0) := 𝑎, b 𝑎 (𝑡+1) := {b 𝑎 (𝑡 ) }. Put F (𝑛) := {𝐹1(𝑛) , 𝐹2(𝑛) , 𝐹3(𝑛) }, SHG (𝑛) := (V, F (𝑛) ). Then Flat(𝐹𝑖(𝑛) ) = 𝑇𝑖 for each 𝑖 by construction, and hence each flattened edge meets both parts: Flat(𝐹1(𝑛) ) ∩ V1 = {𝑈1 } ≠ ∅, Flat(𝐹1(𝑛) ) ∩ V2 = {𝑈3 } ≠ ∅, Flat(𝐹2(𝑛) ) ∩ V1 = {𝑈2 } ≠ ∅, Flat(𝐹2(𝑛) ) ∩ V2 = {𝑈4 , 𝑈5 } ≠ ∅, Flat(𝐹3(𝑛) ) ∩ V1 = {𝑈1 , 𝑈2 } ≠ ∅, Flat(𝐹3(𝑛) ) ∩ V2 = {𝑈4 } ≠ ∅. Therefore SHG (𝑛) is a bipartite 𝑛-superhypergraph with bipartition (V1 , V2 ). Theorem 4.31.6 (Bipartite 𝑛-superhypergraphs generalize bipartite hypergraphs). Fix 𝑛 ≥ 1. For every bipartite hypergraph 𝐻 = (𝑉, E) there exists a bipartite 𝑛-superhypergraph b (𝑛) b F b(𝑛) = V, 𝐻 b(𝑛) by identifying each supervertex with a singleton {𝑣} and flattening each such that 𝐻 is obtained from 𝐻 level-𝑛 superhyperedge to a hyperedge of 𝑉. In particular, the class of bipartite 𝑛-superhypergraphs contains all bipartite hypergraphs as special cases. 128

130.

[beta]

Chapter 4. Some Particular SuperHyperGraphs
Proof. Let 𝐻 = (𝑉, E) be a bipartite hypergraph. Fix a bipartition 𝑉 = 𝐴 ⊔ 𝐵 such that
∀ 𝑒 ∈ E : 𝑒 ∩ 𝐴 ≠ ∅ and 𝑒 ∩ 𝐵 ≠ ∅.
Define the supervertex set by singleton embedding:

b := {𝑣} : 𝑣 ∈ 𝑉 .
V
b → 𝑉 by 𝑓 ({𝑣}) = 𝑣.
Define the vertex-level encoding map 𝑓 : V
For each hyperedge 𝑒 ∈ E define its lifted level-𝑛 superhyperedge by
(𝑛−1)
b
b
𝑒 (𝑛) := 𝑇b𝑒
∈ P 𝑛 ( V),


b
𝑇𝑒 := {𝑣} : 𝑣 ∈ 𝑒 ⊆ V,
and set

 (𝑛)
b (𝑛) := b
F
𝑒 :𝑒∈E .
b (𝑛) ) is an 𝑛-superhypergraph.
b F
b(𝑛) := ( V,
Then 𝐻
Now define the induced bipartition of supervertices:

b𝐴 := {𝑎} : 𝑎 ∈ 𝐴 ,
V


b𝐵 := {𝑏} : 𝑏 ∈ 𝐵 .
V

b=V
b𝐴 ⊔ V
b𝐵 .
Clearly V
(𝑛−1)
b (𝑛) , so b
Take any b
𝑒 (𝑛) ∈ F
𝑒 (𝑛) = 𝑇b𝑒
for some 𝑒 ∈ E. By construction of the lift and the recursive flattening,

Flat(b
𝑒 (𝑛) ) = 𝑇𝑒 = {𝑣} : 𝑣 ∈ 𝑒 .

Hence

b𝐴 = {𝑎} : 𝑎 ∈ 𝑒 ∩ 𝐴 ≠ ∅
Flat(b
𝑒 (𝑛) ) ∩ V
because 𝑒 ∩ 𝐴 ≠ ∅, and similarly

b𝐵 = {𝑏} : 𝑏 ∈ 𝑒 ∩ 𝐵 ≠ ∅
Flat(b
𝑒 (𝑛) ) ∩ V
b(𝑛) is
because 𝑒 ∩ 𝐵 ≠ ∅. Therefore every level-𝑛 superhyperedge meets both sides after flattening, so 𝐻
bipartite.
b with 𝑣 ∈ 𝑉 via 𝑓 . For any 𝑒 ∈ E we have
Finally, identify each supervertex {𝑣} ∈ V
𝑓 [Flat(b
𝑒 (𝑛) )] = 𝑓 [𝑇𝑒 ] = { 𝑓 ({𝑣}) : 𝑣 ∈ 𝑒 } = 𝑒.
b(𝑛) and then applying 𝑓 recovers exactly the hypergraph 𝐻. This proves the claimed
Thus flattening 𝐻
generalization.
□

4.32

Threshold SuperHyperGraph

A threshold graph assigns a nonnegative weight to each vertex and fixes a threshold 𝜏; two vertices are adjacent
exactly when their weights sum to at least 𝜏. Related concepts such as fuzzy threshold graphs [633, 634], mock
threshold graphs [635], neutrosophic threshold graphs [636, 637], bithreshold graphs [638], quasi-threshold
graphs [639–641], and threshold directed graphs [642] are also known. Threshold graphs have simple structure,
admit linear-time recognition, and enable fast solutions for many NP-hard problems on general graphs.
A threshold hypergraph assigns nonnegative
weights to vertices and fixes a threshold 𝜏; a nonempty vertex subset
Í
𝑋 is a hyperedge exactly when 𝑣 ∈𝑋 𝑤(𝑣) ≥ 𝜏 [643–645]. A threshold superhypergraph assigns nonnegative
weights to supervertices
and fixes a threshold 𝜏; a nonempty family 𝑋 of supervertices is a superhyperedge
Í
exactly when 𝑣 ∈𝑋 𝑤(𝑣) ≥ 𝜏. The relevant definitions and related notions are presented below.
Definition 4.32.1 (Threshold graph). [646] A (simple) graph 𝐺 = (𝑉, 𝐸) is a threshold graph if there exist a
weight function 𝑤 : 𝑉 → R ≥0 and a threshold 𝜏 ∈ R ≥0 such that, for all distinct 𝑢, 𝑣 ∈ 𝑉,
{𝑢, 𝑣} ∈ 𝐸

⇐⇒
129

𝑤(𝑢) + 𝑤(𝑣) ≥ 𝜏.

#p287
#p288

131.

[beta]

Chapter 4. Some Particular SuperHyperGraphs
Definition 4.32.2 (Threshold hypergraph). A hypergraph 𝐻 = (𝑉, 𝐸) with 𝐸 ⊆ P (𝑉) \ {∅} is a threshold
hypergraph if there exist a weight function 𝑤 : 𝑉 → R ≥0 and a threshold 𝜏 ∈ R ≥0 such that, for every nonempty
subset 𝑋 ⊆ 𝑉,
∑︁
𝑋 ∈ 𝐸 ⇐⇒
𝑤(𝑣) ≥ 𝜏.
𝑣 ∈𝑋

Example 4.32.3 (A threshold hypergraph). Let
𝑉 := {𝑎, 𝑏, 𝑐},

𝑤(𝑎) = 2, 𝑤(𝑏) = 1, 𝑤(𝑐) = 1,

𝜏 := 3.

Define a hypergraph 𝐻 = (𝑉, 𝐸) by
n

𝐸 :=

𝑋 ⊆ 𝑉 \ {∅}

∑︁

o
𝑤(𝑣) ≥ 𝜏 .

𝑣 ∈𝑋

Then the nonempty subsets 𝑋 ⊆ 𝑉 satisfying the threshold condition are exactly
{𝑎, 𝑏} (𝑤 = 3),

{𝑎, 𝑐} (𝑤 = 3),

{𝑎, 𝑏, 𝑐} (𝑤 = 4),

while {𝑎} has weight 2 < 3, {𝑏} has weight 1 < 3, {𝑐} has weight 1 < 3, and {𝑏, 𝑐} has weight 2 < 3. Hence

𝐸 = {𝑎, 𝑏}, {𝑎, 𝑐}, {𝑎, 𝑏, 𝑐} ,
and 𝐻 is a threshold hypergraph witnessed by (𝑤, 𝜏).
Definition 4.32.4 (Threshold 𝑛-SuperHyperGraph (threshold superhypergraph)). Let 𝑉0 be a finite base set
and define iterated powersets by

P 0 (𝑉0 ) := 𝑉0 ,
P 𝑘+1 (𝑉0 ) := P P 𝑘 (𝑉0 ) (𝑘 ≥ 0).
Fix an integer 𝑛 ≥ 1. An 𝑛-SuperHyperGraph is a pair 𝑆 (𝑛) = (𝑉𝑛 , 𝐸 𝑛 ) such that
𝑉𝑛 ⊆ P 𝑛 (𝑉0 ),

𝐸 𝑛 ⊆ P (𝑉𝑛 ) \ {∅}.

It is called a threshold 𝑛-SuperHyperGraph if there exist a weight function 𝑤 : 𝑉𝑛 → R ≥0 and a threshold
𝜏 ∈ R ≥0 such that, for every nonempty 𝑋 ⊆ 𝑉𝑛 ,
∑︁
𝑋 ∈ 𝐸 𝑛 ⇐⇒
𝑤(𝑣) ≥ 𝜏.
𝑣 ∈𝑋

(When 𝑛 = 1, this is exactly a threshold hypergraph on vertex set 𝑉1 .)
Example 4.32.5 (A threshold 2-SuperHyperGraph). Let the base set be
𝑉0 := {1, 2, 3},
so P 2 (𝑉0 ) = P (P (𝑉0 )). Define three 2-supervertices (elements of P 2 (𝑉0 )) by



𝑠1 := {1} ,
𝑠2 := {2} ,
𝑠3 := {1, 2} ,
and set
𝑉2 := {𝑠1 , 𝑠2 , 𝑠3 } ⊆ P 2 (𝑉0 ).
Assign weights and a threshold by
𝑤(𝑠1 ) = 2,
Define
𝐸 2 :=

n

𝑤(𝑠2 ) = 1,

𝑤(𝑠3 ) = 2,

𝑋 ⊆ 𝑉2 \ {∅}

∑︁

𝜏 := 3.

o
𝑤(𝑠) ≥ 𝜏 .

𝑠∈𝑋

Then
𝑤({𝑠1 , 𝑠2 }) = 3,

𝑤({𝑠1 , 𝑠3 }) = 4,

𝑤({𝑠2 , 𝑠3 }) = 3,

𝑤({𝑠1 , 𝑠2 , 𝑠3 }) = 5,

so these four subsets are superhyperedges, while the singletons have weights 2, 1, 2 < 3 and are not superhyperedges. Therefore

𝐸 2 = {𝑠1 , 𝑠2 }, {𝑠1 , 𝑠3 }, {𝑠2 , 𝑠3 }, {𝑠1 , 𝑠2 , 𝑠3 } ,
and 𝑆 (2) = (𝑉2 , 𝐸 2 ) is a threshold 2-SuperHyperGraph witnessed by (𝑤, 𝜏).
130

132.

[beta]

Chapter 4. Some Particular SuperHyperGraphs

4.33

Fractional SuperHyperGraph

A fractional graph is an equivalence class of finite graphs under fractional (doubly stochastic) relabelings
that transform adjacency consistently (cf. [647–649]). A fractional hypergraph is an equivalence class of
finite hypergraphs under fractional vertex and hyperedge matchings that transform incidence consistently
(cf. [650, 651]). A fractional SuperHyperGraph is an equivalence class of finite n-SuperHyperGraphs under
fractional supervertex and superedge matchings that transform superincidence consistently. The relevant
definitions and related notions are presented below.
Definition 4.33.1 (Doubly stochastic matrix). Let 𝑛 ∈ N. A matrix 𝑆 ∈ R𝑛×𝑛 is called doubly stochastic if
𝑆𝑖 𝑗 ≥ 0 (1 ≤ 𝑖, 𝑗 ≤ 𝑛),

𝑆1 = 1,

𝑆 T 1 = 1,

where 1 is the all-ones column vector in R𝑛 .
Definition 4.33.2 (Fractional graph (fractional-isomorphism viewpoint)). (cf. [647–649]) Let 𝐺 and 𝐻 be finite
directed or undirected graphs on the same number 𝑛 of vertices, and let 𝐴𝐺 , 𝐴 𝐻 ∈ R𝑛×𝑛 be their adjacency
matrices. We say that 𝐺 and 𝐻 are fractionally isomorphic (and write 𝐺  𝑓 𝐻) if there exists a doubly
stochastic matrix 𝑆 ∈ R𝑛×𝑛 such that
𝐴𝐺 𝑆 = 𝑆 𝐴 𝐻 .
A fractional graph can be regarded as an equivalence class
[𝐺] 𝑓 := { 𝐻 | 𝐻  𝑓 𝐺 }
under the relation  𝑓 .
Definition 4.33.3 ((Recall) Incidence matrix of a hypergraph). Let 𝐺 = (𝑉, 𝐸) be a finite hypergraph with
𝑉 = {𝑣 1 , . . . , 𝑣 𝑛 } and 𝐸 = {𝑒 1 , . . . , 𝑒 𝑚 }. Its vertex–hyperedge incidence matrix is the matrix 𝑀𝐺 ∈ {0, 1} 𝑛×𝑚
defined by
(
1, 𝑣 𝑖 ∈ 𝑒 𝑗 ,
(𝑀𝐺 )𝑖 𝑗 :=
0, 𝑣 𝑖 ∉ 𝑒 𝑗 .
Definition 4.33.4 (Fractional hypergraph (fractional-isomorphism viewpoint)). Let 𝐺 and 𝐻 be finite hypergraphs. Write 𝑀𝐺 ∈ {0, 1} 𝑛×𝑚 and 𝑀𝐻 ∈ {0, 1} 𝑛×𝑚 for their incidence matrices (after fixing vertex and
hyperedge orderings). We say that 𝐺 and 𝐻 are fractionally isomorphic (and write 𝐺 ≡ 𝐻) if either

(i) 𝐺 and 𝐻 have the same number of vertices and no hyperedges; or
(ii) there exist doubly stochastic matrices 𝑆1 ∈ R𝑛×𝑛 and 𝑆2 ∈ R𝑚×𝑚 such that
𝑆1 𝑀𝐺 = 𝑀𝐻 𝑆2T

and

𝑀𝐺 𝑆2 = 𝑆1T 𝑀𝐻 .

A fractional hypergraph can be regarded as an equivalence class
[𝐺] ≡ := { 𝐻 | 𝐻 ≡ 𝐺 }
under the relation ≡.
Example 4.33.5 (A concrete fractional hypergraph). Let 𝐺 = (𝑉, 𝐸) and 𝐻 = (𝑉, 𝐹) be 3-uniform hypergraphs
on the same vertex set
𝑉 = {1, 2, 3, 4, 5, 6}.
Define
𝐸 = {𝑒 1 , 𝑒 2 , 𝑒 3 , 𝑒 4 },

𝑒 1 = {1, 2, 3}, 𝑒 2 = {1, 4, 5}, 𝑒 3 = {2, 4, 6}, 𝑒 4 = {3, 5, 6},

𝐹 = { 𝑓1 , 𝑓2 , 𝑓3 , 𝑓4 },

𝑓1 = {1, 2, 3}, 𝑓2 = {1, 2, 4}, 𝑓3 = {3, 5, 6}, 𝑓4 = {4, 5, 6}.

and

131

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133.

Chapter 4. Some Particular SuperHyperGraphs With vertex order (1, 2, 3, 4, 5, 6) and edge orders (𝑒 1 , 𝑒 2 , 𝑒 3 , 𝑒 4 ), ( 𝑓1 , 𝑓2 , 𝑓3 , 𝑓4 ), the incidence matrices are 1 © 1 1 𝑀𝐺 = 0 0 «0 1 0 0 1 1 0 0 1 0 1 0 1 1 © 1 1 𝑀𝐻 = 0 0 «0 0 ª 0® ® 1® ®, 0® ® 1® 1¬ 1 1 0 1 0 0 0 0 1 0 1 1 0 ª 0® ® 0® ®. 1® ® 1® 1¬ Both are (𝑟, 𝑠)-biregular with 𝑟 = 2 (each vertex is in exactly two hyperedges) and 𝑠 = 3 (each hyperedge has size three), i.e. 𝑀𝐺 14 = 216 , 1T6 𝑀𝐺 = 31T4 , 𝑀𝐻 14 = 216 , 1T6 𝑀𝐻 = 31T4 . Let 𝐽 𝑘 denote the 𝑘 × 𝑘 all-ones matrix and set the doubly stochastic matrices 𝑆1 := 1 𝐽6 , 6 𝑆2 := 1 𝐽4 . 4 Then, using 𝐽6 = 16 1T6 and 𝐽4 = 14 1T4 , 𝑆1 𝑀𝐺 = 1 1 1 1 𝐽6 𝑀𝐺 = 16 1T6 𝑀𝐺 = 16 (31T4 ) = 𝐽6×4 , 6 6 6 2 and 1 1 1 1 𝑀𝐻 𝑆2T = 𝑀𝐻 𝐽4 = 𝑀𝐻 14 1T4 = (216 )1T4 = 𝐽6×4 . 4 4 4 2 Similarly, 𝑀𝐺 𝑆2 = 1 1 𝑀𝐺 14 1T4 = 𝐽6×4 4 2 𝑆1T 𝑀𝐻 = and 1 1 16 1T6 𝑀𝐻 = 𝐽6×4 . 6 2 Hence 𝑆1 𝑀𝐺 = 𝑀𝐻 𝑆2T and 𝑀𝐺 𝑆2 = 𝑆1T 𝑀𝐻 , so 𝐺 ≡ 𝐻. Therefore the fractional hypergraph [𝐺] ≡ is a concrete example, and it contains 𝐻. Definition 4.33.6 ((Recall) Incidence matrix of an 𝑛-SuperHyperGraph). Let H (𝑛) = (𝑉 (𝑛) , 𝐸 (𝑛) ) be finite with 𝑉 (𝑛) = {𝑣 1 , . . . , 𝑣 𝑝 }, 𝐸 (𝑛) = {𝑒 1 , . . . , 𝑒 𝑞 }. Its incidence matrix is 𝑀 H (𝑛) ∈ {0, 1} 𝑝×𝑞 defined by ( 𝑀 H (𝑛) 𝑖 𝑗 := 1, 0, 𝑣𝑖 ∈ 𝑒 𝑗 , 𝑣𝑖 ∉ 𝑒 𝑗 . Definition 4.33.7 (Fractional isomorphism of 𝑛-SuperHyperGraphs). Let H (𝑛) = (𝑉 (𝑛) , 𝐸 (𝑛) ) and K (𝑛) = (𝑊 (𝑛) , 𝐹 (𝑛) ) be finite 𝑛-SuperHyperGraphs with |𝑉 (𝑛) | = |𝑊 (𝑛) | = 𝑝, |𝐸 (𝑛) | = |𝐹 (𝑛) | = 𝑞, and incidence matrices 𝑀 H (𝑛) , 𝑀 K (𝑛) ∈ {0, 1} 𝑝×𝑞 after fixing orderings of supervertices and superedges. We say that H (𝑛) and K (𝑛) are fractionally isomorphic (written H (𝑛) ≡𝑛 K (𝑛) ) if there exist doubly stochastic matrices 𝑆𝑉 ∈ R 𝑝× 𝑝 , 𝑆 𝐸 ∈ R𝑞×𝑞 such that 𝑆𝑉 𝑀 H (𝑛) = 𝑀 K (𝑛) 𝑆 T𝐸 and T 𝑀 H (𝑛) 𝑆 𝐸 = 𝑆𝑉 𝑀 K (𝑛) . Definition 4.33.8 (Fractional 𝑛-SuperHyperGraph). A Fractional 𝑛-SuperHyperGraph is an equivalence class [H (𝑛) ] ≡𝑛 := { K (𝑛) | K (𝑛) ≡𝑛 H (𝑛) } under the relation ≡𝑛 of Definition 4.33.7. When 𝑛 is understood, we also call it a Fractional SuperHyperGraph. 132

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134.

[beta]

Chapter 4. Some Particular SuperHyperGraphs
Example 4.33.9 (A concrete fractional SuperHyperGraph (level 𝑛 = 1)). Let the base set be
𝑉0 = {𝑎, 𝑏, 𝑐, 𝑑, 𝑒, 𝑓 },
and define six 1-supervertices (nonempty subsets of 𝑉0 ) by
𝑠1 = {𝑎, 𝑏}, 𝑠2 = {𝑏, 𝑐}, 𝑠3 = {𝑐, 𝑑}, 𝑠4 = {𝑑, 𝑒}, 𝑠5 = {𝑒, 𝑓 }, 𝑠6 = { 𝑓 , 𝑎}.
Consider two 1-SuperHyperGraphs
H (1) = (𝑉 (1) , 𝐸 (1) ),

K (1) = (𝑉 (1) , 𝐹 (1) ),

𝑉 (1) = {𝑠1 , 𝑠2 , 𝑠3 , 𝑠4 , 𝑠5 , 𝑠6 },

with 1-superedges
𝐸 (1) = {𝐸 1 , 𝐸 2 , 𝐸 3 , 𝐸 4 },

𝐸 1 = {𝑠1 , 𝑠2 , 𝑠3 }, 𝐸 2 = {𝑠1 , 𝑠4 , 𝑠5 }, 𝐸 3 = {𝑠2 , 𝑠4 , 𝑠6 }, 𝐸 4 = {𝑠3 , 𝑠5 , 𝑠6 },

𝐹 (1) = {𝐹1 , 𝐹2 , 𝐹3 , 𝐹4 },

𝐹1 = {𝑠1 , 𝑠2 , 𝑠3 }, 𝐹2 = {𝑠1 , 𝑠2 , 𝑠4 }, 𝐹3 = {𝑠3 , 𝑠5 , 𝑠6 }, 𝐹4 = {𝑠4 , 𝑠5 , 𝑠6 }.

and

Using the supervertex order (𝑠1 , . . . , 𝑠6 ) and the superedge orders (𝐸 1 , . . . , 𝐸 4 ) and (𝐹1 , . . . , 𝐹4 ), their incidence
matrices are exactly the matrices 𝑀𝐺 and 𝑀𝐻 from the previous example. In particular, each supervertex is
incident with exactly two superedges and each superedge contains exactly three supervertices.
Let

1
1
𝐽6 ,
𝑆 𝐸 := 𝐽4 ,
6
4
which are doubly stochastic. The same calculation yields
𝑆𝑉 :=

𝑆𝑉 𝑀 H (1) = 𝑀 K (1) 𝑆 T𝐸

and

T
𝑀 H (1) 𝑆 𝐸 = 𝑆𝑉
𝑀 K (1) .

Hence H (1) ≡1 K (1) , so [H (1) ] ≡1 is a concrete Fractional 1-SuperHyperGraph (Fractional SuperHyperGraph),
and it contains K (1) .
Theorem 4.33.10 (SuperHyperGraph representation and generalization of fractional hypergraphs).
(i) Every Fractional 𝑛-SuperHyperGraph [H (𝑛) ] ≡𝑛 has an underlying 𝑛-SuperHyperGraph representative
H (𝑛) in the sense that
H (𝑛) ∈ [H (𝑛) ] ≡𝑛 .
In particular, the notion is built from (and represented by) 𝑛-SuperHyperGraphs.
(ii) For 𝑛 = 0, the notion of Fractional 0-SuperHyperGraph coincides with the notion of Fractional HyperGraph (defined via doubly stochastic matrices acting on the usual vertex–hyperedge incidence matrix).
Concretely, if 𝐻 = (𝑉, 𝐸) is a hypergraph, then viewing it as a 0-SuperHyperGraph H (0) := (𝑉, 𝐸)
yields
[𝐻] ≡ = [H (0) ] ≡0 .
Proof.
(i) By Definition 4.33.8, a Fractional 𝑛-SuperHyperGraph is, by construction, an equivalence class of
𝑛-SuperHyperGraphs under ≡𝑛 . Since ≡𝑛 is an equivalence relation, it is reflexive; hence
H (𝑛) ≡𝑛 H (𝑛) .
Taking 𝑆𝑉 = 𝐼 𝑝 and 𝑆 𝐸 = 𝐼𝑞 (both are doubly stochastic), we have
𝑆𝑉 𝑀 H (𝑛) = 𝐼 𝑝 𝑀 H (𝑛) = 𝑀 H (𝑛) ,

𝑀 H (𝑛) 𝑆 T𝐸 = 𝑀 H (𝑛) 𝐼𝑞 = 𝑀 H (𝑛) ,

𝑀 H (𝑛) 𝑆 𝐸 = 𝑀 H (𝑛) 𝐼𝑞 = 𝑀 H (𝑛) ,

T
𝑆𝑉
𝑀 H (𝑛) = 𝐼 𝑝 𝑀 H (𝑛) = 𝑀 H (𝑛) .

and similarly

Thus the defining equalities of Definition 4.33.7 hold, so H (𝑛) ∈ [H (𝑛) ] ≡𝑛 .
133

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135.

Chapter 4. Some Particular SuperHyperGraphs (ii) Let 𝑛 = 0. Then P0 (𝑉0 ) = 𝑉0 , so an 0-SuperHyperGraph H (0) = (𝑉 (0) , 𝐸 (0) ) is exactly a (finite) hypergraph on vertex set 𝑉 (0) with hyperedges 𝐸 (0) ⊆ P (𝑉 (0) ) \ {∅}. Moreover, the incidence matrix in Definition 4.33.6 is the usual vertex–hyperedge incidence matrix of a hypergraph. Now take two hypergraphs 𝐻 = (𝑉, 𝐸) and 𝐻 ′ = (𝑉 ′ , 𝐸 ′ ) with |𝑉 | = |𝑉 ′ | = 𝑝 and |𝐸 | = |𝐸 ′ | = 𝑞. Identify them with 0-SuperHyperGraphs H (0) := (𝑉, 𝐸), K (0) := (𝑉 ′ , 𝐸 ′ ). Let 𝑀𝐻 and 𝑀𝐻 ′ denote their usual incidence matrices. Under this identification, 𝑀 H (0) = 𝑀𝐻 , 𝑀 K (0) = 𝑀𝐻 ′ . Therefore, the existence of doubly stochastic matrices 𝑆𝑉 ∈ R 𝑝× 𝑝 and 𝑆 𝐸 ∈ R𝑞×𝑞 satisfying the fractional-hypergraph equalities 𝑆𝑉 𝑀𝐻 = 𝑀𝐻 ′ 𝑆 T𝐸 and T 𝑀𝐻 𝑆 𝐸 = 𝑆𝑉 𝑀𝐻 ′ is equivalent (by literal substitution of 𝑀 H (0) and 𝑀 K (0) ) to the equalities 𝑆𝑉 𝑀 H (0) = 𝑀 K (0) 𝑆 T𝐸 and T 𝑀 H (0) 𝑆 𝐸 = 𝑆𝑉 𝑀 K (0) , i.e. to H (0) ≡0 K (0) from Definition 4.33.7. Hence the equivalence classes defined by the two notions coincide: the class of all 𝐻 ′ fractionally isomorphic to 𝐻 is exactly the class of all K (0) fractionally isomorphic to H (0) . This proves [𝐻] ≡ = [H (0) ] ≡0 . □ 4.34 Cycle SuperHyperGraph A cycle graph is a simple graph where vertices form one closed loop, each vertex adjacent to exactly two vertices [652–654]. Several related concepts are also known, such as fuzzy cycle graphs [655, 656], directed cycle graphs [657], and neutrosophic cycle graphs [658]. A cycle hypergraph is a hypergraph admitting a Berge cycle: alternating distinct vertices and hyperedges, each hyperedge containing consecutive vertices [659–661]. A cycle superhypergraph is an n-superhypergraph whose underlying hypergraph contains a Berge cycle, via supervertices and incidence-defined superhyperedges. The relevant definitions and related notions are presented below. Definition 4.34.1 (Cycle graph). (cf. [652–654]) Let ℓ ∈ N with ℓ ≥ 3. The cycle graph of length ℓ is the graph 𝐶ℓ := (𝑉ℓ , 𝐸 ℓ ), where 𝑉ℓ := {𝑣 1 , . . . , 𝑣 ℓ }, 𝐸 ℓ := {𝑣 𝑖 , 𝑣 𝑖+1 } | 𝑖 = 1, . . . , ℓ − 1 ∪ {𝑣 ℓ , 𝑣 1 } . (Here indices are taken modulo ℓ in the obvious way, i.e., 𝑣 ℓ+1 := 𝑣 1 .) Definition 4.34.2 (Berge cycle and cycle hypergraph). Let 𝐻 = (𝑉 (𝐻), 𝐸 (𝐻)) be a finite hypergraph, i.e., 𝑉 (𝐻) ≠ ∅ and 𝐸 (𝐻) ⊆ P ∗ (𝑉 (𝐻)). A Berge cycle of length ℓ ≥ 3 in 𝐻 is an alternating sequence (𝑣 1 , 𝑒 1 , 𝑣 2 , 𝑒 2 , . . . , 𝑣 ℓ , 𝑒 ℓ , 𝑣 1 ) such that 𝑣 1 , . . . , 𝑣 ℓ ∈ 𝑉 (𝐻) are pairwise distinct, 𝑒 1 , . . . , 𝑒 ℓ ∈ 𝐸 (𝐻) are pairwise distinct, and for every 𝑖 ∈ {1, . . . , ℓ}, {𝑣 𝑖 , 𝑣 𝑖+1 } ⊆ 𝑒 𝑖 , where 𝑣 ℓ+1 := 𝑣 1 . A hypergraph 𝐻 is called a cycle hypergraph of length ℓ (in the Berge sense) if 𝐻 has a Berge cycle (𝑣 1 , 𝑒 1 , . . . , 𝑣 ℓ , 𝑒 ℓ , 𝑣 1 ) of length ℓ and moreover 𝑉 (𝐻) = {𝑣 1 , . . . , 𝑣 ℓ }, 𝐸 (𝐻) = {𝑒 1 , . . . , 𝑒 ℓ }. 134

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136.

Chapter 4. Some Particular SuperHyperGraphs Definition 4.34.3 (Underlying hypergraph of an 𝑛-SuperHyperGraph). Let SHG (𝑛) = (𝑉, 𝐸, 𝜕) be an 𝑛SuperHyperGraph (with incidence map 𝜕 : 𝐸 → P ∗ (𝑉)). Its underlying hypergraph is 𝑈 SHG (𝑛) := 𝑉, {𝜕 (𝑒) | 𝑒 ∈ 𝐸 } , which is a hypergraph on vertex set 𝑉 because 𝜕 (𝑒) ∈ P ∗ (𝑉) for all 𝑒 ∈ 𝐸. Definition 4.34.4 (Cycle 𝑛-SuperHyperGraph). An 𝑛-SuperHyperGraph SHG (𝑛) = (𝑉, 𝐸, 𝜕) is called a cycle 𝑛-SuperHyperGraph of length ℓ (Berge type) if its underlying hypergraph 𝑈 (SHG (𝑛) ) is a cycle hypergraph of length ℓ in the sense of Definition 4.34.2. Equivalently, there exist pairwise distinct supervertices 𝑢 1 , . . . , 𝑢 ℓ ∈ 𝑉 and pairwise distinct edges 𝑓1 , . . . , 𝑓ℓ ∈ 𝐸 such that 𝑉 = {𝑢 1 , . . . , 𝑢 ℓ }, {𝜕 ( 𝑓1 ), . . . , 𝜕 ( 𝑓ℓ )} = {𝐹1 , . . . , 𝐹ℓ }, and for each 𝑖, {𝑢 𝑖 , 𝑢 𝑖+1 } ⊆ 𝜕 ( 𝑓𝑖 ), with 𝑢 ℓ+1 := 𝑢 1 . Lemma 4.34.5 (Iterated singleton embedding). Let 𝑉0 be a set and let 𝑛 ∈ N0 . Define a map 𝜄𝑛 : 𝑉0 → P 𝑛 (𝑉0 ) by 𝜄0 (𝑥) := 𝑥, 𝜄 𝑘+1 (𝑥) := {𝜄 𝑘 (𝑥)} (𝑘 ≥ 0). Then: (i) For every 𝑥 ∈ 𝑉0 , one has 𝜄𝑛 (𝑥) ∈ P 𝑛 (𝑉0 ). (ii) The map 𝜄𝑛 is injective. Proof. (i) We prove by induction on 𝑛. If 𝑛 = 0, then 𝜄0 (𝑥) = 𝑥 ∈ 𝑉0 = P 0 (𝑉0 ). Assume 𝜄𝑛 (𝑥) ∈ P 𝑛 (𝑉0 ). Then 𝜄𝑛+1 (𝑥) = {𝜄𝑛 (𝑥)} ⊆ P 𝑛 (𝑉0 ), hence 𝜄𝑛+1 (𝑥) ∈ P P 𝑛 (𝑉0 ) = P 𝑛+1 (𝑉0 ). (ii) We prove by induction on 𝑛. If 𝑛 = 0, then 𝜄0 = id𝑉0 is injective. Assume 𝜄𝑛 is injective. If 𝜄𝑛+1 (𝑥) = 𝜄𝑛+1 (𝑦), then {𝜄𝑛 (𝑥)} = {𝜄𝑛 (𝑦)} =⇒ 𝜄𝑛 (𝑥) = 𝜄𝑛 (𝑦) =⇒ 𝑥 = 𝑦, using injectivity of 𝜄𝑛 . Thus 𝜄𝑛+1 is injective. □ Theorem 4.34.6 (Cycle 𝑛-SuperHyperGraphs generalize cycle hypergraphs). Let 𝐻 = (𝑉 (𝐻), 𝐸 (𝐻)) be a cycle hypergraph of length ℓ in the sense of Definition 4.34.2. Then for every 𝑛 ∈ N0 there exists a cycle 𝑛-SuperHyperGraph CSHG (𝑛) whose underlying hypergraph is isomorphic to 𝐻. In particular, when 𝑛 = 0 one recovers 𝐻 exactly (as a 0-level cycle SuperHyperGraph). Proof. Let 𝐻 = (𝑉 (𝐻), 𝐸 (𝐻)) be a cycle hypergraph of length ℓ. By Definition 4.34.2, there exist pairwise distinct vertices 𝑣 1 , . . . , 𝑣 ℓ and pairwise distinct hyperedges 𝑒 1 , . . . , 𝑒 ℓ such that 𝑉 (𝐻) = {𝑣 1 , . . . , 𝑣 ℓ }, 𝐸 (𝐻) = {𝑒 1 , . . . , 𝑒 ℓ }, {𝑣 𝑖 , 𝑣 𝑖+1 } ⊆ 𝑒 𝑖 (1 ≤ 𝑖 ≤ ℓ), where 𝑣 ℓ+1 := 𝑣 1 . Step 1 (Base set and embedded supervertices). Set the base set 𝑉0 := 𝑉 (𝐻) and define 𝜄𝑛 : 𝑉0 → P 𝑛 (𝑉0 ) as in Lemma 4.34.5. Define 𝑉 (𝑛) := 𝜄𝑛 𝑉 (𝐻) = {𝜄𝑛 (𝑣) | 𝑣 ∈ 𝑉 (𝐻)}. By Lemma 4.34.5(i), 𝑉 (𝑛) ⊆ P 𝑛 (𝑉0 ). Step 2 (Lifted superedges). For each hyperedge 𝑒 ∈ 𝐸 (𝐻) define its lift b 𝑒 (𝑛) := {𝜄𝑛 (𝑣) | 𝑣 ∈ 𝑒}. 135

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[beta]

Chapter 4. Some Particular SuperHyperGraphs
Since 𝑒 ≠ ∅ and 𝜄𝑛 is a function, we have b
𝑒 (𝑛) ≠ ∅. Also b
𝑒 (𝑛) ⊆ 𝑉 (𝑛) , hence b
𝑒 (𝑛) ∈ P ∗ (𝑉 (𝑛) ). Set
𝐸 (𝑛) := {b
𝑒 (𝑛) | 𝑒 ∈ 𝐸 (𝐻)} ⊆ P ∗ (𝑉 (𝑛) ).
Define the incidence map 𝜕 (𝑛) : 𝐸 (𝑛) → P ∗ (𝑉 (𝑛) ) by
𝜕 (𝑛) ( 𝑓 ) := 𝑓

(∀ 𝑓 ∈ 𝐸 (𝑛) ),

i.e., 𝜕 (𝑛) is the identity on the (lifted) edge-set.
Thus
CSHG (𝑛) := 𝑉 (𝑛) , 𝐸 (𝑛) , 𝜕 (𝑛)



is an 𝑛-SuperHyperGraph over 𝑉0 (it satisfies 𝑉 (𝑛) ⊆ P 𝑛 (𝑉0 ) and 𝜕 (𝑛) ( 𝑓 ) ∈ P ∗ (𝑉 (𝑛) ) for all 𝑓 ∈ 𝐸 (𝑛) ).
Step 3 (Cycle property at level 𝑛). Define 𝑢 𝑖 := 𝜄𝑛 (𝑣 𝑖 ) ∈ 𝑉 (𝑛) and 𝑓𝑖 := b
𝑒 𝑖(𝑛) ∈ 𝐸 (𝑛) . Then for each 𝑖,
{𝑢 𝑖 , 𝑢 𝑖+1 } = {𝜄𝑛 (𝑣 𝑖 ), 𝜄𝑛 (𝑣 𝑖+1 )} ⊆ {𝜄𝑛 (𝑣) | 𝑣 ∈ 𝑒 𝑖 } = b
𝑒 𝑖(𝑛) = 𝜕 (𝑛) ( 𝑓𝑖 ),
because {𝑣 𝑖 , 𝑣 𝑖+1 } ⊆ 𝑒 𝑖 in 𝐻. The vertices 𝑢 1 , . . . , 𝑢 ℓ are pairwise distinct by Lemma 4.34.5(ii). Also the
lifted edges 𝑓1 , . . . , 𝑓ℓ are pairwise distinct: if b
𝑒 𝑖(𝑛) = b
𝑒 (𝑛)
𝑒 (𝑛)
𝑗 , then for every 𝑣 ∈ 𝑒 𝑖 we have 𝜄𝑛 (𝑣) ∈ b
𝑗 , so
𝜄𝑛 (𝑣) = 𝜄𝑛 (𝑤) for some 𝑤 ∈ 𝑒 𝑗 ; injectivity of 𝜄𝑛 yields 𝑣 = 𝑤, hence 𝑒 𝑖 ⊆ 𝑒 𝑗 , and similarly 𝑒 𝑗 ⊆ 𝑒 𝑖 , so
𝑒 𝑖 = 𝑒 𝑗 . Therefore 𝑈 (CSHG (𝑛) ) = (𝑉 (𝑛) , 𝐸 (𝑛) ) is a cycle hypergraph of length ℓ, so CSHG (𝑛) is a cycle
𝑛-SuperHyperGraph by Definition 4.34.4.
Step 4 (Isomorphism back to the original cycle hypergraph). The map 𝜄𝑛 : 𝑉 (𝐻) → 𝑉 (𝑛) is a bijection onto its
image by injectivity, and by construction it sends each hyperedge 𝑒 ∈ 𝐸 (𝐻) to the lifted hyperedge b
𝑒 (𝑛) ∈ 𝐸 (𝑛) .
(𝑛)
Hence 𝐻 is isomorphic to the underlying hypergraph 𝑈 (CSHG ).
Finally, if 𝑛 = 0, then 𝜄0 = id𝑉 (𝐻 ) , so
𝑉 (0) = 𝑉 (𝐻),

𝐸 (0) = {b
𝑒 (0) | 𝑒 ∈ 𝐸 (𝐻)} = {𝑒 | 𝑒 ∈ 𝐸 (𝐻)} = 𝐸 (𝐻),

and 𝜕 (0) is the identity. Thus CSHG (0) reproduces 𝐻 exactly.

4.35

□

Friendship SuperHyperGraphs

A friendship graph is a graph where every vertex pair has exactly one common neighbor, forcing triangle−based
“friend” structure [662]. A friendship r−hypergraph is r-uniform: each r-set has a unique external vertex
completing all (𝑟 − 1)-subsets into edges [663–665]. A friendship r−superhypergraph is an (𝑟 + 1)-uniform
block system whose r-subset flattening is friendship, with unique block containment. The relevant definitions
and related notions are presented below.
Definition 4.35.1 (Friendship graph). [662, 666] A (finite, simple) graph 𝐺 = (𝑉, 𝐸) is a friendship graph if
for every two distinct vertices 𝑢, 𝑣 ∈ 𝑉 there exists a unique vertex 𝑤 ∈ 𝑉 \ {𝑢, 𝑣} such that {𝑢, 𝑤} ∈ 𝐸 and
{𝑣, 𝑤} ∈ 𝐸. Equivalently, every pair of vertices has a unique common neighbour.
Definition 4.35.2 (Friendship 𝑟-hypergraph). Fix
 an integer 𝑟 ≥ 2. An 𝑟-uniform hypergraph is a pair
𝐻 = (𝑉, 𝐸) where 𝑉 is a finite set and 𝐸 ⊆ 𝑉𝑟 . We call 𝐻 a friendship 𝑟-hypergraph if for every 𝑅 ∈ 𝑉𝑟
there exists a unique vertex 𝑥 ∈ 𝑉 \ 𝑅 such that


𝑅
𝐴 ∪ {𝑥} ∈ 𝐸 for every 𝐴 ∈
.
𝑟 −1
Such an 𝑥 is called the friend of 𝑅.
Remark 4.35.3. For 𝑟 = 2, a friendship 2-hypergraph is exactly a friendship graph. For 𝑟 = 3, the condition
reads: for every triple {𝑥, 𝑦, 𝑧} there is a unique 𝑤 such that {𝑥, 𝑦, 𝑤}, {𝑥, 𝑧, 𝑤}, {𝑦, 𝑧, 𝑤} are hyperedges.
136

#p136
#p288

138.

[beta]

Chapter 4. Some Particular SuperHyperGraphs
Definition 4.35.4 (𝐾𝑟𝑟+1 on 𝑟+1 vertices). Let 𝑞 ⊆ 𝑉 with |𝑞| = 𝑟 + 1. We say 𝐻 [𝑞] is a copy of 𝐾𝑟𝑟+1 if
 
𝑞
⊆ 𝐸,
𝑟
i.e., every 𝑟-subset of 𝑞 is a hyperedge.
Definition 4.35.5 (Friendship 𝑟-superhypergraph and flattening). Fix 𝑟 ≥ 2. A (uniform) 𝑟-superhypergraph
is a pair


𝑉
S = (𝑉, Q) with Q ⊆
,
𝑟 +1
whose elements are called superhyperedges (or blocks). Its flattening is the 𝑟-uniform hypergraph
Ø 𝑞 
.
Flat(S) := (𝑉, 𝐸 Flat ),
𝐸 Flat :=
𝑟
𝑞∈ Q

We call S a friendship 𝑟-superhypergraph if Flat(S) is a friendship 𝑟-hypergraph and, moreover, every
hyperedge 𝑒 ∈ 𝐸 Flat is contained in a unique block 𝑞 ∈ Q.
Lemma 4.35.6 (Canonical (𝑟+1)-block containing a given hyperedge). Let 𝐻 = (𝑉, 𝐸) be a friendship
𝑟-hypergraph and let 𝑒 ∈ 𝐸. Let 𝑥 be the unique friend of the 𝑟-set 𝑒. Set
𝑞(𝑒) := 𝑒 ∪ {𝑥},
so |𝑞(𝑒)| = 𝑟 + 1. Then:



𝑞(𝑒)
⊆ 𝐸,
𝑟


i.e., 𝐻 [𝑞(𝑒)] is a copy of 𝐾𝑟𝑟+1 . Moreover, 𝑞(𝑒) is the unique (𝑟+1)-subset 𝑞 ⊇ 𝑒 with 𝑞𝑟 ⊆ 𝐸.
Proof. Write 𝑒 = {𝑣 1 , . . . , 𝑣 𝑟 } and
let 𝑥 be the unique friend of 𝑒. By the friendship property applied to 𝑅 = 𝑒,
𝑒 
for every (𝑟 − 1)-subset 𝐴 ∈ 𝑟 −1
we have 𝐴 ∪ {𝑥} ∈ 𝐸. But the 𝑟-subsets of 𝑞(𝑒) = 𝑒 ∪ {𝑥} are exactly:
𝑒

and

(𝑒 \ {𝑣 𝑖 }) ∪ {𝑥} (𝑖 = 1, . . . , 𝑟).

The set 𝑒 is a hyperedge by assumption, and each (𝑒 \ {𝑣 𝑖 }) ∪ {𝑥} is a hyperedge by the friendship property,
hence 𝑞 (𝑒)
⊆ 𝐸.
𝑟

For uniqueness, suppose 𝑞 ⊇ 𝑒 with |𝑞| = 𝑟 + 1 and 𝑞𝑟 ⊆ 𝐸. Then 𝑞 = 𝑒 ∪ {𝑦} for some 𝑦 ∉ 𝑒. Since every
(𝑟 − 1)-subset 𝐴 ⊂ 𝑒 satisfies 𝐴 ∪ {𝑦} ∈ 𝐸, the vertex 𝑦 is a friend of 𝑒. By uniqueness of the friend of 𝑒, we
get 𝑦 = 𝑥, hence 𝑞 = 𝑞(𝑒).
□
Theorem 4.35.7 (Friendship superhypergraphs generalise friendship hypergraphs). Let 𝐻 = (𝑉, 𝐸) be a
friendship 𝑟-hypergraph. Define


𝑉
Q (𝐻) := { 𝑞(𝑒) : 𝑒 ∈ 𝐸 } ⊆
,
S(𝐻) := (𝑉, Q (𝐻)).
𝑟 +1
Then S(𝐻) is a friendship 𝑟-superhypergraph and

Flat S(𝐻) = 𝐻.
In particular, every friendship 𝑟-hypergraph is (canonically) obtained as the flattening of a friendship 𝑟superhypergraph.

Proof. By the lemma, for each 𝑒 ∈ 𝐸 we have 𝑞 (𝑒)
⊆ 𝐸; thus, for every 𝑞 ∈ Q (𝐻),
𝑟
 
𝑞
⊆ 𝐸.
𝑟

Ð
Let 𝐸 Flat := 𝑞∈ Q (𝐻 ) 𝑞𝑟 be the edge set of Flat(S(𝐻)).
137

139.

[beta]

Chapter 4. Some Particular SuperHyperGraphs

First, 𝐸 ⊆ 𝐸 Flat : take any 𝑒 ∈ 𝐸; then 𝑒 ⊆ 𝑞(𝑒) ∈ Q (𝐻), hence 𝑒 ∈ 𝑞 (𝑒)
⊆ 𝐸 Flat .
𝑟


Second, 𝐸 Flat ⊆ 𝐸: take any 𝑓 ∈ 𝐸 Flat ; then 𝑓 ∈ 𝑞𝑟 for some 𝑞 ∈ Q (𝐻), and we already know 𝑞𝑟 ⊆ 𝐸, hence
𝑓 ∈ 𝐸.
Therefore 𝐸 Flat = 𝐸, so Flat(S(𝐻)) = (𝑉, 𝐸) = 𝐻.
Finally, the lemma also shows that each 𝑒 ∈ 𝐸 is contained in exactly one block 𝑞(𝑒) ∈ Q (𝐻), so S(𝐻) satisfies
the defining uniqueness condition of a friendship 𝑟-superhypergraph.
□

4.36

Wheel SuperHyperGraph

A wheel graph has one hub vertex joined to all cycle vertices, plus the cycle edges connecting consecutive rim
vertices [667–669]. Related notions such as fuzzy wheel graphs [670–673], Double-Wheel graphs [674–676],
and their variants are also known. A wheel hypergraph has rim hyperedges on consecutive rim vertices and
spoke hyperedges containing the hub with consecutive rim vertices (cf. [677]). A wheel 𝑛-superhypergraph
replaces each vertex by an (𝑛−1)-fold singleton lift and lifts each wheel hyperedge accordingly. The relevant
definitions and related notions are presented below.
Definition 4.36.1 (Wheel graph). [667–669] Let 𝑁 ≥ 4. Put
𝑉0 := {ℎ} ∪ {𝑣 1 , 𝑣 2 , . . . , 𝑣 𝑁 −1 }.
The wheel graph 𝑊 𝑁 is the simple graph (𝑉0 , 𝐸) with


𝐸 := {𝑣 𝑖 , 𝑣 𝑖+1 } : 1 ≤ 𝑖 ≤ 𝑁 − 1 ∪ {ℎ, 𝑣 𝑖 } : 1 ≤ 𝑖 ≤ 𝑁 − 1 ,
where indices on rim vertices are taken modulo 𝑁 − 1 (so 𝑣 𝑁 := 𝑣 1 ).
Definition 4.36.2 (Wheel 𝑟-uniform hypergraph). Let 𝑟 ≥ 2 and 𝑁 ≥ 𝑟 + 1. With the same vertex set
𝑉0 := {ℎ} ∪ {𝑣 1 , . . . , 𝑣 𝑁 −1 },
(𝑟 )
define the wheel 𝑟-uniform hypergraph 𝑊 𝑁(𝑟 ) = (𝑉0 , E 𝑁
) by
(𝑟 )
E𝑁
:= {𝑅𝑖 , 𝑆𝑖 : 1 ≤ 𝑖 ≤ 𝑁 − 1},

where, using indices modulo 𝑁 − 1 (so 𝑣 𝑁 −1+ 𝑗 := 𝑣 𝑗 ),
𝑅𝑖 := {𝑣 𝑖 , 𝑣 𝑖+1 , . . . , 𝑣 𝑖+𝑟 −1 },

𝑆𝑖 := {ℎ, 𝑣 𝑖 , 𝑣 𝑖+1 , . . . , 𝑣 𝑖+𝑟 −2 }.

Thus every hyperedge has size 𝑟, and 𝑅𝑖 are rim hyperedges while 𝑆𝑖 are spoke hyperedges.
Definition 4.36.3 (Singleton lifting). Fix 𝑉0 and an integer 𝑡 ≥ 0. For each 𝑥 ∈ 𝑉0 define recursively
 (𝑡 )
b
𝑥 (0) := 𝑥,
b
𝑥 (𝑡+1) := b
𝑥
.
Then b
𝑥 (𝑡 ) ∈ P 𝑡 (𝑉0 ) for every 𝑡 ≥ 0.
(𝑟 )
Definition 4.36.4 (Wheel (𝑛, 𝑟)-superhypergraph). Let 𝑟 ≥ 2, 𝑁 ≥ 𝑟 + 1, and 𝑛 ≥ 1. Let 𝑊 𝑁(𝑟 ) = (𝑉0 , E 𝑁
) be
the wheel 𝑟-uniform hypergraph.

Define the (𝑛 − 1)-level lifted vertex family
 (𝑛−1)
V𝑁(𝑛−1) := b
𝑥
: 𝑥 ∈ 𝑉0 ⊆ P 𝑛−1 (𝑉0 ).
(𝑟 )
For each hyperedge 𝑒 ∈ E 𝑁
define its 𝑛-lift by
 (𝑛−1)
b
𝑒 (𝑛) := b
𝑥
: 𝑥 ∈ 𝑒 ⊆ V𝑁(𝑛−1) .

Set

 (𝑛)
(𝑛)
(𝑟 )
E𝑁
𝑒 : 𝑒 ∈ E𝑁
.
,𝑟 := b

The wheel (𝑛, 𝑟)-superhypergraph is
(𝑛)
(𝑛) 
W𝑁
,𝑟 := 𝑉0 , E 𝑁 ,𝑟 .

138

#p288
#p289

140.

Chapter 4. Some Particular SuperHyperGraphs Example 4.36.5 (A concrete wheel (𝑛, 𝑟)-superhypergraph). Take 𝑛 = 2, 𝑟 = 3, 𝑁 = 5. Let the base vertex set be 𝑉0 = {ℎ, 1, 2, 3, 4}, where ℎ is the hub and 1, 2, 3, 4 are the rim vertices (with indices taken modulo 4). Define the wheel 3-uniform hypergraph 𝑊5(3) = (𝑉0 , E5(3) ) by specifying its hyperedge family as the union of rim-triangles and spoke-triangles: n o n o E5(3) := {𝑖, 𝑖 + 1, 𝑖 + 2} : 𝑖 ∈ {1, 2, 3, 4} ∪ {ℎ, 𝑖, 𝑖 + 1} : 𝑖 ∈ {1, 2, 3, 4} , where arithmetic on {1, 2, 3, 4} is modulo 4 (so 4 + 1 = 1, etc.). Concretely, E5(3) = {{1, 2, 3}, {2, 3, 4}, {3, 4, 1}, {4, 1, 2}} ∪ {{ℎ, 1, 2}, {ℎ, 2, 3}, {ℎ, 3, 4}, {ℎ, 4, 1}}. Since 𝑛 = 2, the (𝑛 − 1)-level lifted vertex family is the collection of singletons: (1) V5(1) = b 𝑥 : 𝑥 ∈ 𝑉0 = {ℎ}, {1}, {2}, {3}, {4} ⊆ P (𝑉0 ). For each 𝑒 ∈ E5(3) its 2-lift is (1) b 𝑒 (2) = b 𝑥 : 𝑥 ∈ 𝑒 = {𝑥} : 𝑥 ∈ 𝑒 ⊆ V5(1) . Hence the lifted hyperedge family is n o (2) E5,3 = b 𝑒 (2) : 𝑒 ∈ E5(3) , for instance (2) {1, 2, 3} = {{1}, {2}, {3}}, (2) {ℎ, 3, 4} = {{ℎ}, {3}, {4}}. Therefore the wheel (2, 3)-superhypergraph on 𝑁 = 5 vertices is (2) (2) W5,3 = 𝑉0 , E5,3 , whose superhyperedges are exactly the 2-lifts of the eight 3-hyperedges listed above. (𝑛) Theorem 4.36.6 (Well-definedness: W 𝑁 ,𝑟 is an 𝑛-SuperHyperGraph). For 𝑟 ≥ 2, 𝑁 ≥ 𝑟 + 1, and 𝑛 ≥ 1, the (𝑛) (𝑛) pair W 𝑁 ,𝑟 = (𝑉0 , E 𝑁 ,𝑟 ) is an 𝑛-superhypergraph on 𝑉0 . Proof. By construction, V𝑁(𝑛−1) ⊆ P 𝑛−1 (𝑉0 ). (𝑛) (𝑟 ) Take any b 𝑒 (𝑛) ∈ E 𝑁 𝑒 (𝑛) = {b 𝑥 (𝑛−1) : 𝑥 ∈ 𝑒} for some 𝑒 ∈ E 𝑁 . Since 𝑒 ≠ ∅, the set b 𝑒 (𝑛) is nonempty. ,𝑟 . Then b (𝑛) 𝑛−1 Also, by definition, every element of b 𝑒 lies in P (𝑉0 ). Hence b 𝑒 (𝑛) ∈ P∗ P 𝑛−1 (𝑉0 ) . Therefore (𝑛) ∗ 𝑛−1 (𝑉0 ) , E𝑁 ,𝑟 ⊆ P P (𝑛) so W 𝑁 ,𝑟 is an 𝑛-superhypergraph on 𝑉0 . □ 139

141.

[beta]

Chapter 4. Some Particular SuperHyperGraphs

4.37

Submodular SuperHypergraph

A submodular graph assigns each edge a submodular cut function, producing a global cut cost via weighted
summation always consistently [678–680]. A submodular hypergraph equips every hyperedge with a submodular splitting penalty, so cut evaluations aggregate weighted within-hyperedge variations for subsets [681]. A
submodular superhypergraph uses supervertices from iterated powersets and superedges with submodular cut
functions, extending hypergraphs hierarchically across abstraction levels. The relevant definitions and related
notions are presented below.
Definition 4.37.1 (Submodular set function). [682–684] Let 𝑈 be a finite set. A function 𝑓 : 2𝑈 → R is
submodular if for all 𝐴, 𝐵 ⊆ 𝑈,
𝑓 ( 𝐴) + 𝑓 (𝐵) ≥ 𝑓 ( 𝐴 ∩ 𝐵) + 𝑓 ( 𝐴 ∪ 𝐵).
Definition 4.37.2 (Submodular cut function on a hyperedge). Let ℎ be a finite set. A function 𝛿 ℎ : 2ℎ → [0, 1]
is called a submodular cut function if (i) 𝛿 ℎ is submodular (as a set function on 2ℎ ), and (ii) 𝛿 ℎ (∅) = 𝛿 ℎ (ℎ) = 0.
Definition 4.37.3 (Submodular graph). [678–680] A submodular graph is a tuple
𝐺 = (𝑉, 𝐸, 𝑤, {𝛿𝑒 } 𝑒∈𝐸 )
such that

 
𝑉
𝐸⊆
,
𝑤 : 𝐸 → R>0 ,
2
and for every edge 𝑒 = {𝑢, 𝑣} ∈ 𝐸, the function 𝛿𝑒 : 2𝑒 → [0, 1] is a submodular cut function.
For any 𝑆 ⊆ 𝑉, the induced cut-cost is
𝛿𝐺 (𝑆) :=

∑︁

𝑤(𝑒) 𝛿𝑒 (𝑆 ∩ 𝑒).

𝑒∈𝐸

(Example: the standard undirected edge-cut is 𝛿 {𝑢,𝑣 } (𝑆) = |1𝑆 (𝑢) − 1𝑆 (𝑣)|.)
Example 4.37.4 (A concrete submodular graph). Let

𝐸 = {1, 2}, {2, 3} .

𝑉 = {1, 2, 3},
Assign positive weights
𝑤({1, 2}) = 2,

𝑤({2, 3}) = 1.

For each edge 𝑒 = {𝑢, 𝑣} define the (normalized) cut function
(
0, 𝑇 = ∅ or 𝑇 = 𝑒,
𝛿𝑒 (𝑇) :=
1, 𝑇 = {𝑢} or 𝑇 = {𝑣},

(𝑇 ⊆ 𝑒).

This 𝛿𝑒 is submodular on the ground set 𝑒 (it is the usual edge-cut on {𝑢, 𝑣}).
Hence, for any 𝑆 ⊆ 𝑉,
𝛿𝐺 (𝑆) = 2 𝛿 {1,2} (𝑆 ∩ {1, 2}) + 1 𝛿 {2,3} (𝑆 ∩ {2, 3}).
For example, if 𝑆 = {1} then
𝑆 ∩ {1, 2} = {1} ⇒ 𝛿 {1,2} = 1,

𝑆 ∩ {2, 3} = ∅ ⇒ 𝛿 {2,3} = 0,

so 𝛿𝐺 ({1}) = 2 · 1 + 1 · 0 = 2.
Definition 4.37.5 (Submodular hypergraph). A submodular hypergraph is a tuple
𝐻 = (𝑉, 𝐸, 𝑤, {𝛿 ℎ } ℎ∈𝐸 )
such that
𝐸 ⊆ 2𝑉 \ {∅},
and for every hyperedge ℎ ∈ 𝐸, the function 𝛿 ℎ

𝑤 : 𝐸 → R>0 ,
ℎ
: 2 → [0, 1] is a submodular cut function.

For any 𝑆 ⊆ 𝑉, define
𝛿 𝐻 (𝑆) :=

∑︁

𝑤(ℎ) 𝛿 ℎ (𝑆 ∩ ℎ).
ℎ∈𝐸
(Example: the standard hypergraph cut function is 𝛿cut
ℎ (𝑇) = min{1, |𝑇 |, |ℎ \ 𝑇 |} for 𝑇 ⊆ ℎ.)
140

#p289

142.

[beta]

Chapter 4. Some Particular SuperHyperGraphs
Example 4.37.6 (A concrete submodular hypergraph). Let
𝑉 = {𝑎, 𝑏, 𝑐, 𝑑},

𝐸 = {ℎ1 , ℎ2 },

ℎ1 = {𝑎, 𝑏, 𝑐}, ℎ2 = {𝑏, 𝑐, 𝑑}.

𝑤(ℎ1 ) = 3,

𝑤(ℎ2 ) = 1.

Assign weights
Define for each hyperedge ℎ the standard (normalized) hypergraph cut function
𝛿 ℎ (𝑇) := min{1, |𝑇 |, |ℎ \ 𝑇 |},

(𝑇 ⊆ ℎ).

It is submodular on 2ℎ .
Thus, for any 𝑆 ⊆ 𝑉,
𝛿 𝐻 (𝑆) = 3 𝛿 ℎ1 (𝑆 ∩ ℎ1 ) + 1 𝛿 ℎ2 (𝑆 ∩ ℎ2 ).
For example, take 𝑆 = {𝑎, 𝑑}. Then
𝑆 ∩ ℎ1 = {𝑎} ⇒ 𝛿 ℎ1 (𝑆 ∩ ℎ1 ) = min{1, 1, 2} = 1,
𝑆 ∩ ℎ2 = {𝑑} ⇒ 𝛿 ℎ2 (𝑆 ∩ ℎ2 ) = min{1, 1, 2} = 1,
so
𝛿 𝐻 ({𝑎, 𝑑}) = 3 · 1 + 1 · 1 = 4.
Definition 4.37.7 (Submodular 𝑛-SuperHyperGraph). Fix a finite base set 𝑉0 and an integer 𝑛 ≥ 0. A
(vertex-)level 𝑛-SuperHyperGraph is a pair
H = (V, E)
where
V ⊆ P 𝑛 (𝑉0 ) \ {∅}

(supervertices),

E ⊆ 2 V \ {∅}

(superedges).

A submodular 𝑛-SuperHyperGraph is a tuple
H = (V, E, 𝑤, {𝛿𝑒 } 𝑒∈ E )
with 𝑤 : E → R>0 and, for each superedge 𝑒 ∈ E, a submodular cut function 𝛿𝑒 : 2𝑒 → [0, 1].
For any S ⊆ V, define the cut-cost
𝛿 H (S) :=

∑︁

𝑤(𝑒) 𝛿𝑒 (S ∩ 𝑒).

𝑒∈ E

If 𝑛 = 0 and we identify each base vertex 𝑣 ∈ 𝑉0 with the singleton {𝑣} ∈ P (𝑉0 ), then V ⊆ 𝑉0 and this
definition reduces to a submodular hypergraph; furthermore, if all edges have size 2, it reduces to a submodular
graph.
Example 4.37.8 (A concrete submodular 𝑛-SuperHyperGraph (take 𝑛 = 1)). Let the base set be
𝑉0 = {1, 2, 3},

𝑛 = 1.

Define the supervertex family (nonempty subsets of 𝑉0 )

V := {1}, {2}, {3}, {1, 2} ⊆ P 1 (𝑉0 ) \ {∅}.
Define two superedges (each is a nonempty subset of V):


𝑒 1 := {1}, {2}, {1, 2} ,
𝑒 2 := {2}, {3} ,
Assign weights
𝑤(𝑒 1 ) = 2,

𝑤(𝑒 2 ) = 5.

Define submodular cut functions as follows.
141

E := {𝑒 1 , 𝑒 2 }.

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Chapter 4. Some Particular SuperHyperGraphs
(1) For 𝑒 2 (a 2-element ground set), use the standard edge-cut:
(
0, 𝑇 = ∅ or 𝑇 = 𝑒 2 ,
𝛿𝑒2 (𝑇) :=
1, otherwise,

(𝑇 ⊆ 𝑒 2 ).

(2) For 𝑒 1 (a 3-element ground set), use the normalized cardinality cut
𝛿𝑒1 (𝑇) := min{1, |𝑇 |, |𝑒 1 \ 𝑇 |},

(𝑇 ⊆ 𝑒 1 ).

This is submodular on 2𝑒1 .
Therefore, for any S ⊆ V,
𝛿 H (S) = 2 𝛿𝑒1 (S ∩ 𝑒 1 ) + 5 𝛿𝑒2 (S ∩ 𝑒 2 ).
Example evaluation: let

S = {1}, {3} ⊆ V.
Then

S ∩ 𝑒 1 = {1} ⇒ 𝛿𝑒1 (S ∩ 𝑒 1 ) = min{1, 1, 2} = 1,

S ∩ 𝑒 2 = {3} ⇒ 𝛿𝑒2 (S ∩ 𝑒 2 ) = 1,
so
𝛿 H (S) = 2 · 1 + 5 · 1 = 7.

4.38

Multipartite SuperHypergraph

A multipartite graph partitions vertices into 𝑘 disjoint parts, and every edge connects two vertices from different
parts only [685–688]. Multipartite graphs model multi-group interactions, forbid within-group edges, simplify
constraints, and enable efficient colorings, matchings, and partition-based optimizations.
A multipartite hypergraph partitions vertices into 𝑘 disjoint parts, and each hyperedge contains at most one
vertex from each part [689–692]. A multipartite superhypergraph partitions 𝑛-supervertices into 𝑘 disjoint
classes, and each superhyperedge selects one supervertex from each class. The relevant definitions and related
notions are presented below.
Definition 4.38.1 (𝑘-partite graph; multipartite graph).
[693–695] Let 𝑘 ≥ 2. A (simple) graph is a pair

𝐺 = (𝑉, 𝐸) where 𝑉 is a set of vertices and 𝐸 ⊆ 𝑉2 is a set of (2-element) edges. We say that 𝐺 is 𝑘-partite
if there exist pairwise disjoint sets 𝑉1 , . . . , 𝑉𝑘 such that
𝑉 = 𝑉1 ∪¤ · · · ∪¤ 𝑉𝑘
and for every edge {𝑢, 𝑣} ∈ 𝐸 there exist indices 𝑖 ≠ 𝑗 with 𝑢 ∈ 𝑉𝑖 and 𝑣 ∈ 𝑉 𝑗 . If 𝐺 is 𝑘-partite for some 𝑘 ≥ 2,
then 𝐺 is called multipartite.
Definition 4.38.2 (𝑘-uniform multipartite hypergraph). Let 𝑘 ≥ 2. A 𝑘-uniform multipartite hypergraph is a
hypergraph 𝐻 = (𝑉, E) for which there exist pairwise disjoint vertex classes 𝑉1 , . . . , 𝑉𝑘 such that
𝑉 = 𝑉1 ∪¤ · · · ∪¤ 𝑉𝑘 ,
and the hyperedge family E can be represented as a set of 𝑘-tuples
E ⊆ 𝑉1 × · · · × 𝑉𝑘 ,
where each hyperedge 𝑒 = (𝑣 1 , . . . , 𝑣 𝑘 ) ∈ E corresponds to the 𝑘-element subset {𝑣 1 , . . . , 𝑣 𝑘 } ⊆ 𝑉, equivalently
satisfying |{𝑣 1 , . . . , 𝑣 𝑘 } ∩ 𝑉𝑖 | = 1 for all 𝑖 = 1, . . . , 𝑘.
142

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Chapter 4. Some Particular SuperHyperGraphs Example 4.38.3 (A 3-uniform multipartite hypergraph). Let 𝑘 = 3 and let the vertex classes be 𝑉1 := {𝑎 1 , 𝑎 2 }, 𝑉2 := {𝑏 1 , 𝑏 2 }, 𝑉3 := {𝑐 1 , 𝑐 2 }, ¤ 2 ∪𝑉 ¤ 3. 𝑉 := 𝑉1 ∪𝑉 Define the hyperedge family by the set of 3-tuples E ⊆ 𝑉1 × 𝑉2 × 𝑉3 , E := {(𝑎 1 , 𝑏 1 , 𝑐 1 ), (𝑎 2 , 𝑏 1 , 𝑐 2 ), (𝑎 2 , 𝑏 2 , 𝑐 1 )}. Equivalently, the three hyperedges (as 3-element subsets of 𝑉) are {𝑎 1 , 𝑏 1 , 𝑐 1 }, {𝑎 2 , 𝑏 1 , 𝑐 2 }, {𝑎 2 , 𝑏 2 , 𝑐 1 }. Each hyperedge meets every class 𝑉𝑖 in exactly one vertex, so 𝐻 = (𝑉, E) is 3-uniform multipartite. Definition 4.38.4 (𝑘-uniform multipartite 𝑛-superhypergraph). Let 𝑛 ≥ 1 and 𝑘 ≥ 2. Let 𝑉0,1 , . . . , 𝑉0,𝑘 be pairwise disjoint nonempty base sets, and define the 𝑘 vertex classes by 𝑉𝑖 := P 𝑛−1 (𝑉0,𝑖 ) (𝑖 = 1, . . . , 𝑘). A 𝑘-uniform multipartite 𝑛-superhypergraph is a hypergraph 𝐻 = (𝑉, E) such that 𝑉 = 𝑉1 ∪¤ · · · ∪¤ 𝑉𝑘 , E ⊆ 𝑉1 × · · · × 𝑉𝑘 , and each hyperedge 𝑒 = (𝑣 1 , . . . , 𝑣 𝑘 ) ∈ E selects exactly one (super)vertex 𝑣 𝑖 ∈ 𝑉𝑖 from each class. In particular, when 𝑛 = 1 we have 𝑉𝑖 = P 0 (𝑉0,𝑖 ) = 𝑉0,𝑖 , so the above definition reduces to the usual 𝑘-uniform multipartite hypergraph on the base vertex classes. Example 4.38.5 (A 3-uniform multipartite 𝑛-superhypergraph (take 𝑛 = 2)). Let 𝑛 = 2 and 𝑘 = 3. Take pairwise disjoint base sets 𝑉0,1 := {1, 2}, 𝑉0,2 := {3, 4}, 𝑉0,3 := {5, 6}. Then 𝑉𝑖 = P 𝑛−1 (𝑉0,𝑖 ) = P (𝑉0,𝑖 ) (𝑖 = 1, 2, 3), so explicitly 𝑉1 = {1}, {2}, {1, 2} , 𝑉2 = {3}, {4}, {3, 4} , 𝑉3 = {5}, {6}, {5, 6} , and ¤ 2 ∪𝑉 ¤ 3. 𝑉 := 𝑉1 ∪𝑉 Define the hyperedge family by a set of triples E ⊆ 𝑉1 × 𝑉2 × 𝑉3 , n o E := ({1, 2}, {3}, {5}), ({2}, {3, 4}, {6}) . Equivalently, the hyperedges (as 3-element subsets of 𝑉) are {1, 2}, {3}, {5} , {2}, {3, 4}, {6} . Each hyperedge chooses exactly one supervertex from each class 𝑉1 , 𝑉2 , 𝑉3 , hence 𝐻 = (𝑉, E) is a 3-uniform multipartite 2-superhypergraph in the stated sense. 4.39 Annotated HyperGraph and SuperHyperGraph Annotated HyperGraph is a hypergraph equipped with additional labels or metadata on vertices, hyperedges, or incidences to represent roles, attributes, or contextual information beyond connectivity (cf. [696, 697]). Annotated SuperHyperGraph is a higher-order hypergraph built via iterated powerset-based objects, where vertices and superhyperedges also carry annotations describing hierarchical roles, attributes, and context [698]. The relevant definitions and related notions are presented below. 143

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Chapter 4. Some Particular SuperHyperGraphs
Definition 4.39.1 (Annotated HyperGraph). [696, 697] Let 𝑉 be a finite set (vertices). Let 𝐸 be a finite
hyperedge multiset such that every 𝑒 ∈ 𝐸 is a nonempty subset of 𝑉 (parallel hyperedges are allowed). Let 𝑋
be a finite set (role labels). An Annotated HyperGraph is a quadruple
𝐻 = (𝑉, 𝐸, 𝑋, 𝜑),
where the role-labeling function is
𝜑 : {(𝑣, 𝑒) ∈ 𝑉 × 𝐸 | 𝑣 ∈ 𝑒} −→ 𝑋.
For each incidence (𝑣, 𝑒) with 𝑣 ∈ 𝑒, the value 𝜑(𝑣, 𝑒) ∈ 𝑋 specifies the role of 𝑣 inside the hyperedge 𝑒.
Example 4.39.2 (Annotated HyperGraph: Project-Team Roles). Let
𝑉 = {Alice, Bob, Carol, Dave},

𝑋 = {Manager, Developer, Tester}.

Let the hyperedge multiset be 𝐸 = {𝑃1 , 𝑃2 } with
𝑃1 = {Alice, Bob, Carol},

𝑃2 = {Bob, Carol, Dave}.

Define 𝜑 on incidences by
𝜑(Alice, 𝑃1 ) = Manager, 𝜑(Bob, 𝑃1 ) = Developer, 𝜑(Carol, 𝑃1 ) = Tester,
𝜑(Bob, 𝑃2 ) = Manager, 𝜑(Carol, 𝑃2 ) = Developer, 𝜑(Dave, 𝑃2 ) = Tester.
Then 𝐻 = (𝑉, 𝐸, 𝑋, 𝜑) is an annotated hypergraph in which each member has an explicit role in each projecthyperedge.
Definition 4.39.3 (Annotated 𝑛-SuperHyperGraph). [698] Let 𝑆 be a nonempty base set and let 𝑛 ≥ 0 be an
integer. Define iterated powersets recursively by

P 0 (𝑆) = 𝑆,
P 𝑘+1 (𝑆) = P P 𝑘 (𝑆) (𝑘 ≥ 0).
An Annotated 𝑛-SuperHyperGraph is a quadruple
𝐻 = (𝑉, 𝐸, 𝑋, 𝜑),
where:
(1) 𝑉 ⊆ P 𝑛 (𝑆) is a finite set of 𝑛-supervertices;
(2) 𝐸 is a finite 𝑛-superedge multiset with 𝐸 ⊆ P (𝑉), and each 𝑒 ∈ 𝐸 is a nonempty subset of 𝑉 (parallel
superedges are allowed);
(3) 𝑋 is a finite set of role labels;
(4) 𝜑 is the role-labeling function
𝜑 : {(𝑣, 𝑒) ∈ 𝑉 × 𝐸 | 𝑣 ∈ 𝑒} −→ 𝑋.
Thus 𝜑(𝑣, 𝑒) = 𝑥 means that the 𝑛-supervertex 𝑣 plays role 𝑥 in the 𝑛-superedge 𝑒.
Example 4.39.4 (Annotated 2-SuperHyperGraph: Cross-Department Projects). Let the base set of employees
be
𝑆 = {Alice, Bob, Carol, Dave, Eve, Frank}.
Choose first-level teams (elements of P 1 (𝑆) = P (𝑆)):
𝑇1 = {Alice, Bob},

𝑇2 = {Carol, Dave},

𝑇3 = {Eve, Frank}.

Define second-level departments (elements of P 2 (𝑆) = P (P (𝑆))):
𝐷 1 = {𝑇1 , 𝑇2 },

𝐷 2 = {𝑇2 , 𝑇3 }.
144

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Chapter 4. Some Particular SuperHyperGraphs Let the set of 2-supervertices be 𝑉 = {𝐷 1 , 𝐷 2 } ⊆ P 2 (𝑆) and let 𝑋 = {Coordinator, Contributor}. Define two cross-department projects (superedges) by 𝑒 𝐴 = {𝐷 1 , 𝐷 2 }, 𝑒 𝐵 = {𝐷 2 }, 𝐸 = {𝑒 𝐴, 𝑒 𝐵 } ⊆ P (𝑉). Define the role-labeling function 𝜑 on incidences by 𝜑(𝐷 1 , 𝑒 𝐴) = Coordinator, 𝜑(𝐷 2 , 𝑒 𝐴) = Contributor, 𝜑(𝐷 2 , 𝑒 𝐵 ) = Coordinator. Then 𝐻 = (𝑉, 𝐸, 𝑋, 𝜑) is an annotated 2-superhypergraph, where each department plays an explicit role in each cross-department project. 4.40 Chordal 𝑛-SuperHyperGraph A chordal graph is a graph in which every cycle of length at least four contains a chord, equivalently, it has no induced cycles of length at least four [699–701]. In addition, for chordal graphs, related concepts such as fuzzy chordal graphs [702–704] , strongly chordal graphs [705, 706], proper chordal graphs [707], cochordal graphs [708, 709], dually chordal graphs [710, 711], locally chordal graphs [712], and directed chordal graphs [713] are also known. Chordal graphs admit perfect elimination orderings and clique trees, enabling efficient algorithms for coloring, maximum clique, and many NP-hard problems on general graphs. A chordal hypergraph is a hypergraph whose two-section (primal) graph is chordal, meaning that whenever two vertices lie in some common hyperedge, they are adjacent in a chordal graph [714, 715]. A chordal superhypergraph is an 𝑛-SuperHyperGraph whose two-section graph on supervertices is chordal, so the inducedcycle obstruction is excluded at the supervertex level. The relevant definitions and related notions are presented below. Definition 4.40.1 (Chordal graph). [699–701] Let 𝐺 = (𝑉, 𝐸) be a finite simple undirected graph. A chord of a cycle 𝐶 = 𝑣 1 𝑣 2 · · · 𝑣 𝑘 𝑣 1 (𝑘 ≥ 4) is an edge {𝑣 𝑖 , 𝑣 𝑗 } ∈ 𝐸 with |𝑖 − 𝑗 | . 1 (mod 𝑘). The graph 𝐺 is chordal if every cycle of length at least 4 has a chord. Equivalently, 𝐺 has no induced cycle of length ≥ 4. Definition 4.40.2 (Two-section (shadow) graph of a hypergraph). Let 𝐻 = (𝑉, E) be a finite hypergraph, i.e. ∅ ≠ 𝑉 and E ⊆ P (𝑉) \ {∅}. The two-section graph (or shadow graph) of 𝐻 is the graph Γ(𝐻) = (𝑉, 𝐸 2 ), {𝑢, 𝑣} ∈ 𝐸 2 ⇐⇒ 𝑢 ≠ 𝑣 and ∃ 𝑒 ∈ E with {𝑢, 𝑣} ⊆ 𝑒. Definition 4.40.3 (Chordal hypergraph). A finite hypergraph 𝐻 is chordal if its two-section graph Γ(𝐻) is chordal in the sense of Definition 4.40.1. Example 4.40.4 (A chordal hypergraph). Let 𝑉 := {1, 2, 3, 4} and E := {1, 2, 3}, {1, 3, 4} . Define the hypergraph 𝐻 := (𝑉, E). Its two-section graph Γ(𝐻) has vertex set 𝑉 and edges joining any two vertices that appear together in a hyperedge. Hence 𝐸 Γ(𝐻) = {1, 2}, {2, 3}, {1, 3}, {1, 4}, {3, 4} . Equivalently, Γ(𝐻) is obtained from the 4-cycle (2, 1, 4, 3, 2) by adding the chord {1, 3}. Therefore every cycle of length at least 4 in Γ(𝐻) has a chord, so Γ(𝐻) is chordal. By Definition 4.40.3, the hypergraph 𝐻 is chordal. Definition 4.40.5 (Two-section graph of an 𝑛-SuperHyperGraph). Let 𝑛 ∈ N0 and let SHG (𝑛) = (𝑉, 𝐸, 𝜕) be a finite 𝑛-SuperHyperGraph (with incidence map 𝜕 : 𝐸 → P ∗ (𝑉)). Its two-section graph is Γ SHG (𝑛) = (𝑉, 𝐸 2 ), {𝑈, 𝑊 } ∈ 𝐸 2 ⇐⇒ 𝑈 ≠ 𝑊 and ∃ 𝑒 ∈ 𝐸 with {𝑈, 𝑊 } ⊆ 𝜕 (𝑒). 145

147.

Chapter 4. Some Particular SuperHyperGraphs Example 4.40.6 (Two-section graph of a 1-SuperHyperGraph). Let the base set be 𝑉0 := {1, 2, 3, 4} and define the 1-level supervertex set 𝑉 := {1}, {2}, {3}, {4} ⊆ P (𝑉0 ) \ {∅}. Let the edge-identifier set be 𝐸 := {𝑎, 𝑏} and define the incidence map 𝜕 : 𝐸 → P ∗ (𝑉) by 𝜕 (𝑎) := {1}, {2}, {3} , 𝜕 (𝑏) := {1}, {3}, {4} . Then SHG (1) := (𝑉, 𝐸, 𝜕) is a finite 1-SuperHyperGraph. By Definition 4.40.5, its two-section graph Γ(SHG (1) ) = (𝑉, 𝐸 2 ) satisfies {𝑈, 𝑊 } ∈ 𝐸 2 ⇐⇒ 𝑈 ≠ 𝑊 and ∃𝑒 ∈ {𝑎, 𝑏} with {𝑈, 𝑊 } ⊆ 𝜕 (𝑒). Thus the edges are exactly the pairs of supervertices that co-occur in some incidence set: 𝐸 2 = {{1}, {2}}, {{2}, {3}}, {{1}, {3}}, {{1}, {4}}, {{3}, {4}} . So Γ(SHG (1) ) is the graph on {{1}, {2}, {3}, {4}} whose adjacency is induced by the two incidence triples 𝜕 (𝑎) and 𝜕 (𝑏). Definition 4.40.7 (Chordal 𝑛-SuperHyperGraph). An 𝑛-SuperHyperGraph SHG (𝑛) is chordal if Γ SHG (𝑛) is chordal as a graph (Definitions 4.40.5 and 4.40.1). Example 4.40.8 (A chordal 1-SuperHyperGraph). Consider the same 1-SuperHyperGraph SHG (1) = (𝑉, 𝐸, 𝜕) as in Example 4.40.6. We claim that SHG (1) is chordal in the sense of Definition 4.40.7. Indeed, Example 4.40.6 computed Γ(SHG (1) ) explicitly and showed that it is the graph on four vertices obtained from the 4-cycle ({2}, {1}, {4}, {3}, {2}) by adding the chord {{1}, {3}}. Hence Γ(SHG (1) ) is chordal as a graph. Therefore, by Definition 4.40.7, SHG (1) is a chordal 1-SuperHyperGraph. Theorem 4.40.9 (Chordal 𝑛-SuperHyperGraphs generalize chordal hypergraphs). Let 𝐻 = (𝑉, E) be a finite hypergraph. Define the associated 0-SuperHyperGraph SHG (0) (𝐻) := (𝑉, 𝐸, 𝜕) by taking 𝐸 := E and 𝜕 (𝑒) := 𝑒 for all 𝑒 ∈ 𝐸. Then 𝐻 is chordal (Definition 4.40.3) ⇐⇒ SHG (0) (𝐻) is chordal (Definition 4.40.7). Consequently, the notion of chordal 𝑛-SuperHyperGraph extends (contains) the notion of chordal hypergraph as the special case 𝑛 = 0. Proof. Let 𝐻 = (𝑉, E) be given and form SHG (0) (𝐻) = (𝑉, 𝐸, 𝜕) with 𝐸 = E and 𝜕 (𝑒) = 𝑒 for all 𝑒 ∈ 𝐸. By Definition 4.40.2, {𝑢, 𝑣} ∈ 𝐸 Γ(𝐻) ⇐⇒ 𝑢 ≠ 𝑣 and ∃ 𝑒 ∈ E with {𝑢, 𝑣} ⊆ 𝑒. Since 𝐸 = E and 𝜕 (𝑒) = 𝑒, Definition 4.40.5 gives {𝑢, 𝑣} ∈ 𝐸 Γ SHG (0) (𝐻) ⇐⇒ 𝑢 ≠ 𝑣 and ∃ 𝑒 ∈ 𝐸 with {𝑢, 𝑣} ⊆ 𝜕 (𝑒) ⇐⇒ 𝑢 ≠ 𝑣 and ∃ 𝑒 ∈ E with {𝑢, 𝑣} ⊆ 𝑒. Hence the edge sets coincide: Γ(𝐻) = Γ SHG (0) (𝐻) . Therefore Γ(𝐻) is chordal if and only if Γ(SHG (0) (𝐻)) is chordal, i.e., 𝐻 is chordal (Definition 4.40.3) if and only if SHG (0) (𝐻) is chordal (Definition 4.40.7). □ 146

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Chapter 4. Some Particular SuperHyperGraphs 4.41 Kneser SuperHypergraph A Kneser graph connects two 𝑘-subsets of [𝑛] by an edge exactly when the subsets are disjoint [132, 716, 717]. Related concepts such as the Bipartite Kneser graph [718, 719] and the generalized Kneser graph [720, 721] are also known. A Kneser hypergraph uses 𝑘-subsets of [𝑛] as vertices, and forms r-uniform hyperedges from r pairwise disjoint vertices [722,723]. A Kneser superhypergraph uses 𝑘-subsets as vertices, takes blocks of 𝑟 + 1 pairwise disjoint vertices, and flattens blocks into 𝑟-hyperedges. The relevant definitions and related notions are presented below. Notation 4.41.1. For 𝑛 ∈ N write [𝑛] := {1, 2, . . . , 𝑛}. For a finite set 𝑋 and integer 𝑘 ≥ 0, write 𝑋 := {𝐴 ⊆ 𝑋 : | 𝐴| = 𝑘 }. 𝑘 A family F of sets is pairwise disjoint if 𝐴 ∩ 𝐵 = ∅ for all distinct 𝐴, 𝐵 ∈ F . Definition 4.41.2 (Kneser graph KG(𝑛, 𝑘)). [132, 716, 717] Let 𝑛, 𝑘 be integers with 𝑛 ≥ 2𝑘. The Kneser graph KG(𝑛, 𝑘) is the simple graph with [𝑛] [𝑛] , 𝐸 KG(𝑛, 𝑘) := {𝐴, 𝐵} : 𝐴, 𝐵 ∈ 𝑉 KG(𝑛, 𝑘) := , 𝐴∩𝐵=∅ . 𝑘 𝑘 Equivalently, two 𝑘-subsets are adjacent iff they are disjoint. Definition 4.41.3 (Kneser 𝑟-uniform hypergraph KG (𝑟 ) (𝑛, 𝑘)). Fix integers 𝑟 ≥ 2 and 𝑛, 𝑘 with 𝑛 ≥ 𝑟 𝑘. The Kneser 𝑟-uniform hypergraph (also called the Kneser 𝑟-graph) KG (𝑟 ) (𝑛, 𝑘) is the 𝑟-uniform hypergraph with vertex set [𝑛] 𝑉 KG (𝑟 ) (𝑛, 𝑘) := , 𝑘 and hyperedge set 𝐸 KG (𝑟 ) n (𝑛, 𝑘) := 𝑒 ∈ [𝑛] 𝑘 o : 𝑒 is a pairwise disjoint family of 𝑘-subsets . 𝑟 Thus 𝑒 = {𝐴1 , . . . , 𝐴𝑟 } is a hyperedge iff 𝐴𝑖 ∩ 𝐴 𝑗 = ∅ for all 𝑖 ≠ 𝑗. Remark 4.41.4. For 𝑟 = 2, the hypergraph KG (2) (𝑛, 𝑘) is exactly the graph KG(𝑛, 𝑘). Definition 4.41.5 (Uniform (𝑟+1)-block 𝑛-superhypergraph and flattening). Fix integers 𝑟 ≥ 2 and 𝑛 ≥ 1. A uniform (𝑟+1)-block 𝑛-superhypergraph is a pair S = (𝑉, Q (𝑛) ) such that, with the (𝑛 − 1)-level lifted vertex family V (𝑛−1) := {b 𝑥 ( 𝑛−1) : 𝑥 ∈ 𝑉 } ⊆ P 𝑛−1 (𝑉), the block family satisfies Q (𝑛) ⊆ V (𝑛−1) . 𝑟 +1 Its flattening is the 𝑟-uniform hypergraph on the lifted vertex set (𝑛) Flat(S) := V (𝑛−1) , 𝐸 Flat , (𝑛) 𝐸 Flat := Ø 𝑞 . 𝑟 (𝑛) 𝑞∈ Q Definition 4.41.6 (Kneser (𝑟+1)-block 𝑛-superhypergraph). Fix integers 𝑟 ≥ 2, 𝑛 ≥ 1, 𝑁 ≥ 1, and 𝑘 ≥ 1 with 𝑁 ≥ (𝑟 + 1)𝑘 147

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149.

Chapter 4. Some Particular SuperHyperGraphs (so that (𝑟 + 1) pairwise disjoint 𝑘-subsets of [𝑁] exist). Let the base set be [𝑁] 𝑉 := 𝑉𝑁 ,𝑘 = . 𝑘 Define the lifted vertex family at level (𝑛 − 1) by b( 𝑛−1) : 𝐴 ∈ V𝑁(𝑛−1) := { 𝐴 ,𝑘 [𝑁] } ⊆ P 𝑛−1 (𝑉). 𝑘 For every pairwise disjoint family 𝑞 0 = {𝐴0 , 𝐴1 , . . . , 𝐴𝑟 } ∈ 𝑉 , 𝑟 +1 define its 𝑛-level block (a subset of P 𝑛−1 (𝑉)) by 𝑞b0 (𝑛) := { c 𝐴0 ( 𝑛−1) ( 𝑛−1) ( 𝑛−1) ,c 𝐴1 ,..., c 𝐴𝑟 } ∈ V𝑁(𝑛−1) ,𝑘 . 𝑟 +1 Define the block family n (𝑛) (𝑛) Q𝑁 ,𝑘,𝑟 := 𝑞b0 𝑞0 ∈ o 𝑉 and 𝑞 0 is pairwise disjoint . 𝑟 +1 The Kneser (𝑟+1)-block 𝑛-superhypergraph is (𝑛) (𝑛) KG 𝑁 ,𝑘,𝑟 := 𝑉, Q 𝑁 ,𝑘,𝑟 . Theorem 4.41.7 (Well-definedness as an 𝑛-superhypergraph). For all parameters as in Definition 4.41.6, the (𝑛) structure KG 𝑁 ,𝑘,𝑟 is a well-defined uniform (𝑟+1)-block 𝑛-superhypergraph in the sense of Definition 4.41.5. Proof. Let 𝑉 = [ 𝑁 ] 𝑘 . b( 𝑛−1) ∈ P 𝑛−1 (𝑉). Hence Step 1 (lifted vertices lie in P 𝑛−1 (𝑉)). For each 𝐴 ∈ 𝑉 we have 𝐴 b( 𝑛−1) : 𝐴 ∈ 𝑉 } ⊆ P 𝑛−1 (𝑉). V𝑁(𝑛−1) = {𝐴 ,𝑘 (𝑛−1) V𝑁 ,𝑘 𝑟+1 Step 2 (each block has size 𝑟 + 1 and lies in 𝑉 c ( 𝑛−1) ∈ V (𝑛−1) for each 𝑖, so 𝑟+1 . Then 𝐴𝑖 𝑁 ,𝑘 𝑞b0 (𝑛) = { c 𝐴0 ). Take any pairwise disjoint family 𝑞 0 = {𝐴0 , . . . , 𝐴𝑟 } ∈ ( 𝑛−1) ( 𝑛−1) ,..., c 𝐴𝑟 } ⊆ V𝑁(𝑛−1) ,𝑘 . Also |𝑞 0 | = 𝑟 + 1 implies | 𝑞b0 (𝑛) | = 𝑟 + 1, hence 𝑞b0 (𝑛) ∈ V𝑁(𝑛−1) ,𝑘 . 𝑟 +1 (𝑛) (𝑛−1) By Step 2, every element of Q 𝑁 ,𝑘,𝑟 is an (𝑟 + 1)-subset of V𝑁 ,𝑘 . Therefore (𝑛) Q𝑁 ,𝑘,𝑟 ⊆ V𝑁(𝑛−1) ,𝑘 , 𝑟 +1 (𝑛) (𝑛) so KG 𝑁 ,𝑘,𝑟 = (𝑉, Q 𝑁 ,𝑘,𝑟 ) is a uniform (𝑟 + 1)-block 𝑛-superhypergraph as required. 148 □

#p148

150.

Chapter 4. Some Particular SuperHyperGraphs (𝑛) Theorem 4.41.8 (Flattening and projection recover the Kneser hypergraph). Let KG 𝑁 ,𝑘,𝑟 be as in Definition 4.41.6, and form its flattening (𝑛) (𝑛−1) (𝑛) Flat KG 𝑁 ,𝑘,𝑟 = V𝑁 ,𝑘 , 𝐸 Flat . Define the projection map Proj : V𝑁(𝑛−1) → 𝑉𝑁 ,𝑘 , ,𝑘 b( 𝑛−1) := 𝐴. Proj 𝐴 Let the projected 𝑟-uniform hypergraph be (𝑛) (𝑛) Proj∗ Flat KG 𝑁 := 𝑉𝑁 ,𝑘 , {Proj[𝑒] : 𝑒 ∈ 𝐸 Flat } , ,𝑘,𝑟 Then Proj[𝑒] := {Proj(𝑈) : 𝑈 ∈ 𝑒}. (𝑛) Proj∗ Flat KG 𝑁 = KG (𝑟 ) (𝑁, 𝑘). ,𝑘,𝑟 (𝑛) In particular, KG 𝑁 ,𝑘,𝑟 determines the classical Kneser 𝑟-uniform hypergraph via flattening and projection. Proof. Let 𝑉 := 𝑉𝑁 ,𝑘 = Write [ 𝑁 ] and V (𝑛−1) := V𝑁(𝑛−1) 𝑘 ,𝑘 . o n 𝑉 𝐸 (𝑟 ) := 𝐸 KG (𝑟 ) (𝑁, 𝑘) = 𝑒 ∈ : the 𝑘-sets in 𝑒 are pairwise disjoint , 𝑟 and 𝑞 . 𝑟 Ø (𝑛) 𝐸 Flat = (𝑛) 𝑞∈ Q 𝑁 ,𝑘,𝑟 We prove the two inclusions (𝑛) {Proj[𝑒] : 𝑒 ∈ 𝐸 Flat } ⊆ 𝐸 (𝑟 ) and (𝑛) Step 1 (first inclusion). Take any 𝑒 ∈ 𝐸 Flat . Then 𝑒 ∈ there exists a pairwise disjoint family (𝑛) 𝐸 (𝑟 ) ⊆ {Proj[𝑒] : 𝑒 ∈ 𝐸 Flat }. (𝑛) (𝑛) 𝑞 𝑟 for some block 𝑞 ∈ Q 𝑁 ,𝑘,𝑟 . By definition of Q 𝑁 ,𝑘,𝑟 , 𝑉 𝑞 0 = {𝐴0 , . . . , 𝐴𝑟 } ∈ 𝑟 +1 such that ( 𝑛−1) ( 𝑛−1) 𝑞 = 𝑞b0 (𝑛) = { c 𝐴0 ,..., c 𝐴𝑟 }. Since 𝑒 ⊆ 𝑞, we may write c𝑖1 ( 𝑛−1) , . . . , 𝐴 c𝑖𝑟 ( 𝑛−1) } 𝑒 = {𝐴 b( 𝑛−1) ) = 𝐴 yields for distinct indices 𝑖1 , . . . , 𝑖𝑟 . Applying Proj( 𝐴 Proj[𝑒] = {𝐴𝑖1 , . . . , 𝐴𝑖𝑟 }. Because the 𝐴 𝑗 are pairwise disjoint, the subfamily {𝐴𝑖1 , . . . , 𝐴𝑖𝑟 } is also pairwise disjoint. Hence Proj[𝑒] ∈ 𝐸 (𝑟 ) . This proves (𝑛) {Proj[𝑒] : 𝑒 ∈ 𝐸 Flat } ⊆ 𝐸 (𝑟 ) . Step 2 (second inclusion). Let 𝑓 = {𝐴1 , . . . , 𝐴𝑟 } ∈ 𝐸 (𝑟 ) . Then 𝐴1 , . . . , 𝐴𝑟 are pairwise disjoint 𝑘-subsets of [𝑁]. Therefore 𝑟 𝑟 Ø ∑︁ 𝐴𝑖 = | 𝐴𝑖 | = 𝑟 𝑘. 𝑖=1 𝑖=1 Since 𝑁 ≥ (𝑟 + 1)𝑘, we have |[𝑁] \ Ð𝑟 𝑖=1 𝐴𝑖 | = 𝑁 − 𝑟 𝑘 ≥ 𝑘, 149

#p148

151.

Chapter 4. Some Particular SuperHyperGraphs so we can choose a 𝑘-subset 𝐵∈ [𝑁] \ Ð𝑟 𝑖=1 𝐴𝑖 . 𝑘 Then 𝐵 is disjoint from each 𝐴𝑖 , so 𝑞 0 := {𝐴1 , . . . , 𝐴𝑟 , 𝐵} ∈ 𝑉 𝑟 +1 is a pairwise disjoint family. Hence its lift 𝑞 := 𝑞b0 (𝑛) = { c 𝐴1 ( 𝑛−1) ( 𝑛−1) ,..., c 𝐴𝑟 b( 𝑛−1) } ,𝐵 (𝑛) lies in Q 𝑁 ,𝑘,𝑟 . Now set 𝑒 := { c 𝐴1 ( 𝑛−1) ( 𝑛−1) ,..., c 𝐴𝑟 }∈ 𝑞 (𝑛) ⊆ 𝐸 Flat . 𝑟 Applying Proj gives Proj[𝑒] = {𝐴1 , . . . , 𝐴𝑟 } = 𝑓 . (𝑛) Thus 𝑓 ∈ {Proj[𝑒] : 𝑒 ∈ 𝐸 Flat }, proving (𝑛) 𝐸 (𝑟 ) ⊆ {Proj[𝑒] : 𝑒 ∈ 𝐸 Flat }. Steps 1–2 give equality of the 𝑟-edge families after projection, and the vertex set is 𝑉𝑁 ,𝑘 on both sides. Therefore (𝑛) Proj∗ Flat KG 𝑁 = KG (𝑟 ) (𝑁, 𝑘). ,𝑘,𝑟 □ 4.42 Turán SuperHyperGraph A Turán graph 𝑇 (𝑛, 𝑘) is the complete balanced 𝑘-partite graph on 𝑛 vertices, maximizing edges among all 𝐾 𝑘+1 -free graphs [724–726]. A Turán 𝑟-hypergraph 𝑇𝑟 (𝑛, 𝑘) is the complete 𝑘-partite 𝑟-uniform hypergraph (𝑟 ) on 𝑛 vertices, maximizing hyperedges under forbidding 𝐾 𝑘+1 . A Turán 𝑟-superhypergraph is a block system whose 𝑟-flattening equals the Turán 𝑟-hypergraph, encoding hierarchical constraints via superhyperedges. The relevant definitions and related notions are presented below. Definition 4.42.1 (Balanced 𝑘-partition). Let 𝑉 be a Ã finite set with |𝑉 | = 𝑛 and let 𝑘 ≥ 2. A family 𝑘 V = {𝑉1 , . . . , 𝑉𝑘 } is a balanced 𝑘-partition of 𝑉 if 𝑉 = 𝑖=1 𝑉𝑖 and ||𝑉𝑖 | − |𝑉 𝑗 || ≤ 1 for all 𝑖, 𝑗. Definition 4.42.2 (Turán graph). [724–726] Let 𝑛 ≥ 1 and 𝑘 ≥ 2. Fix a balanced 𝑘-partition V = {𝑉1 , . . . , 𝑉𝑘 } of a vertex set 𝑉 with |𝑉 | = 𝑛. The Turán graph 𝑇2 (𝑛, 𝑘) is the complete 𝑘-partite simple graph on 𝑉: 𝐸 𝑇2 (𝑛, 𝑘) := {𝑢, 𝑣} ⊆ 𝑉 : 𝑢 ∈ 𝑉𝑖 , 𝑣 ∈ 𝑉 𝑗 , 𝑖 ≠ 𝑗 . Definition 4.42.3 (Turán 𝑟-hypergraph). Let 𝑛 ≥ 1, 𝑘 ≥ 2, and 𝑟 ≥ 2. Fix a balanced 𝑘-partition V = {𝑉1 , . . . , 𝑉𝑘 } of 𝑉 with |𝑉 | = 𝑛. The Turán 𝑟-hypergraph 𝑇𝑟 (𝑛, 𝑘) is the 𝑟-uniform hypergraph (𝑉, 𝐸) where n o 𝑉 𝐸 𝑇𝑟 (𝑛, 𝑘) := 𝑒 ∈ : |𝑒 ∩ 𝑉𝑖 | ≤ 1 for every 𝑖 ∈ {1, . . . , 𝑘 } . 𝑟 (Equivalently, the hyperedges are exactly the 𝑟-sets that choose vertices from 𝑟 distinct parts.) Definition 4.42.4 (Balanced 𝑘-partition). Let 𝑉0 be a finite set with |𝑉0 | = 𝑁 ≥ 1 and let 𝑘 ≥ 2. A family V = {𝑈1 , . . . , 𝑈 𝑘 } is called a balanced 𝑘-partition of 𝑉0 if 𝑉0 = 𝑘 Ä 𝑈𝑖 and |𝑈𝑖 | − |𝑈 𝑗 | ≤ 1 for all 𝑖, 𝑗 . 𝑖=1 150

#p290

152.

[beta]

Chapter 4. Some Particular SuperHyperGraphs
Definition 4.42.5 (Iterated singleton embedding). Let 𝑛 ∈ N0 and let 𝑉0 be a set. Define 𝜄𝑛 : 𝑉0 → P 𝑛 (𝑉0 )
recursively by
𝜄0 (𝑥) := 𝑥,
𝜄𝑡+1 (𝑥) := {𝜄𝑡 (𝑥)} (𝑡 ≥ 0).
For a subset 𝑆 ⊆ 𝑉0 we write
𝜄𝑛 (𝑆) := {𝜄𝑛 (𝑥) | 𝑥 ∈ 𝑆} ⊆ P 𝑛 (𝑉0 ).
Definition 4.42.6 (Turán 𝑟-superhypergraph as an 𝑛-SuperHyperGraph). Let 𝑁 ≥ 1, 𝑘 ≥ 2, 𝑟 ≥ 2, and 𝑛 ∈ N0 .
Fix a balanced 𝑘-partition V = {𝑈1 , . . . , 𝑈 𝑘 } of a base set 𝑉0 with |𝑉0 | = 𝑁.
Define the 𝑛-supervertex set
𝑉𝑖(𝑛) := 𝜄𝑛 (𝑈𝑖 ) (1 ≤ 𝑖 ≤ 𝑘).

𝑉 (𝑛) := 𝜄𝑛 (𝑉0 ) ⊆ P 𝑛 (𝑉0 ),

Define the block family Q by
n
o

(𝑛) 


𝜄𝑛 (𝑆) ∈ 𝑉 𝑟
: 𝑆 ∈ 𝑉𝑟0 , |𝑆 ∩ 𝑈𝑖 | ≤ 1 for all 𝑖 ,



o

n
(𝑛) 
𝑉0 
Q :=
𝜄𝑛 (𝑆) ∈ 𝑉𝑟+1 : 𝑆 ∈ 𝑟+1
, |𝑆 ∩ 𝑈𝑖 | ≤ 1 for all 𝑖 ,




 ∅,


if 𝑘 = 𝑟,
if 𝑘 ≥ 𝑟 + 1,
if 𝑘 < 𝑟.

Now define the Turán 𝑟-superhypergraph of level 𝑛 by the triple

T𝑟 (𝑛) (𝑁, 𝑘, 𝑟) := 𝑉 (𝑛) , 𝐸 (𝑛) , 𝜕 ,
where 𝐸 (𝑛) := Q ⊆ P (𝑉 (𝑛) ) and the incidence map is
𝜕 : 𝐸 (𝑛) → P∗ (𝑉 (𝑛) ),

𝜕 (𝑞) := 𝑞 for all 𝑞 ∈ 𝐸 (𝑛) .

Theorem 4.42.7 (Well-definedness: T𝑟 (𝑛) (𝑁, 𝑘, 𝑟) is an 𝑛-SuperHyperGraph). The structure T𝑟 (𝑛) (𝑁, 𝑘, 𝑟) in
Definition 4.42.6 is an 𝑛-SuperHyperGraph over the base set 𝑉0 .

Proof. We verify the three required conditions.
Step 1: 𝑉 (𝑛) ⊆ P 𝑛 (𝑉0 ). By definition, each element of 𝑉 (𝑛) has the form 𝜄𝑛 (𝑥) for some 𝑥 ∈ 𝑉0 . The map 𝜄𝑛
was defined so that 𝜄𝑛 (𝑥) ∈ P 𝑛 (𝑉0 ) for every 𝑥 ∈ 𝑉0 . Hence
𝑉 (𝑛) = 𝜄𝑛 (𝑉0 ) ⊆ P 𝑛 (𝑉0 ).

Step 2: 𝐸 (𝑛) ⊆ P (𝑉 (𝑛) ). By construction, every block in Q is of the form 𝜄𝑛 (𝑆) for some 𝑆 ⊆ 𝑉0 , so
𝜄𝑛 (𝑆) ⊆ 𝜄𝑛 (𝑉0 ) = 𝑉 (𝑛) . Therefore each 𝑞 ∈ Q is a subset of 𝑉 (𝑛) , and hence
𝐸 (𝑛) = Q ⊆ P (𝑉 (𝑛) ).

Step 3: 𝜕 : 𝐸 (𝑛) → P∗ (𝑉 (𝑛) ) is well-defined. If 𝑞 ∈ 𝐸 (𝑛) , then 𝑞 ≠ ∅ because 𝑞 = 𝜄𝑛 (𝑆) with |𝑆| = 𝑟 or
|𝑆| = 𝑟 + 1. Also 𝑞 ⊆ 𝑉 (𝑛) by Step 2. Thus 𝑞 ∈ P∗ (𝑉 (𝑛) ), and since 𝜕 (𝑞) = 𝑞 we obtain
𝜕 (𝑞) ∈ P∗ (𝑉 (𝑛) )

for all 𝑞 ∈ 𝐸 (𝑛) .

This proves that T𝑟 (𝑛) (𝑁, 𝑘, 𝑟) = (𝑉 (𝑛) , 𝐸 (𝑛) , 𝜕) satisfies the definition of an 𝑛-SuperHyperGraph over 𝑉0 . □
151

#p152

153.

[beta]

Chapter 4. Some Particular SuperHyperGraphs
Definition 4.42.8 (Flattening to an 𝑟-uniform hypergraph). Let T𝑟 (𝑛) (𝑁, 𝑘, 𝑟) = (𝑉 (𝑛) , 𝐸 (𝑛) , 𝜕) be as in
Definition 4.42.6. Define the projection 𝜋 : 𝑉 (𝑛) → 𝑉0 by
𝜋(𝜄𝑛 (𝑥)) := 𝑥

(𝑥 ∈ 𝑉0 ),

and for 𝑋 ⊆ 𝑉 (𝑛) define 𝜋(𝑋) := {𝜋(𝑣) | 𝑣 ∈ 𝑋 } ⊆ 𝑉0 .
The 𝑟-flattening of T𝑟 (𝑛) (𝑁, 𝑘, 𝑟) is the 𝑟-uniform hypergraph

Flat T𝑟 (𝑛) (𝑁, 𝑘, 𝑟) := (𝑉0 , 𝐸 Flat ),

𝐸 Flat :=

Ø  𝜋(𝜕 (𝑞)) 
.
𝑟
(𝑛)

𝑞 ∈𝐸

Theorem 4.42.9 (Turán superhypergraphs generalize Turán hypergraphs via flattening). Let 𝑁 ≥ 1, 𝑘 ≥ 2,
𝑟 ≥ 2, and 𝑛 ∈ N0 . With the same balanced 𝑘-partition V of 𝑉0 ,

Flat T𝑟 (𝑛) (𝑁, 𝑘, 𝑟) = 𝑇𝑟 (𝑁, 𝑘, 𝑟).

Proof. Let V = {𝑈1 , . . . , 𝑈 𝑘 } be fixed. Write 𝐸𝑇 for the edge set and 𝐸 Flat for the edge set in Definition 4.42.8.
Case 1: 𝑘 < 𝑟. Then no 𝑟-subset can meet each part in at most one vertex because there are fewer than 𝑟 parts,
so 𝐸𝑇 = ∅. Also Definition 4.42.6 gives 𝐸 (𝑛) = ∅, hence 𝐸 Flat = ∅. Thus 𝐸 Flat = 𝐸𝑇 .
Case 2: 𝑘 = 𝑟. Here each block 𝑞 ∈ 𝐸 (𝑛) has size 𝑟 and equals 𝜄𝑛 (𝑆) for a unique 𝑆 ∈
|𝑆 ∩ 𝑈𝑖 | ≤ 1 for all 𝑖. Moreover 𝜋(𝑞) = 𝑆, and 𝜕 (𝑞) = 𝑞, hence

 
  
𝜋(𝜕 (𝑞))
𝜋(𝑞)
𝑆
=
=
= {𝑆}.
𝑟
𝑟
𝑟

𝑉0 
𝑟 satisfying

Therefore
Ø  𝜋(𝜕 (𝑞)) 
Ø
𝐸 Flat =
{𝑆} = 𝐸𝑇 .
=
𝑟
(𝑛)
𝑆 ∈𝐸
𝑞∈𝐸

𝑇

Case 3: 𝑘 ≥ 𝑟 + 1. In this case each block 𝑞 ∈ 𝐸 (𝑛) has size 𝑟 + 1 and equals 𝜄𝑛 (𝑆) for some 𝑆 ∈
|𝑆 ∩ 𝑈𝑖 | ≤ 1 for all 𝑖. We prove the two inclusions 𝐸 Flat ⊆ 𝐸𝑇 and 𝐸𝑇 ⊆ 𝐸 Flat .

𝑉0 
𝑟+1 with

)
𝐸 Flat ⊆ 𝐸𝑇 . Take any 𝑒 ∈ 𝐸 Flat . Then 𝑒 ∈ 𝜋 (𝜕(𝑞)
for some 𝑞 ∈ 𝐸 (𝑛) . Since 𝜕 (𝑞) = 𝑞 and 𝑞 = 𝜄𝑛 (𝑆) for some
𝑟
𝑆 meeting each 𝑈𝑖 in at most one vertex, we have 𝜋(𝑞) = 𝑆 and hence 𝑒 ⊆ 𝑆 with |𝑒| = 𝑟. Because 𝑆 meets
each part 𝑈𝑖 in at most one vertex, every subset 𝑒 ⊆ 𝑆 also satisfies

|𝑒 ∩ 𝑈𝑖 | ≤ 1

for all 𝑖,

so 𝑒 ∈ 𝐸𝑇 . This proves 𝐸 Flat ⊆ 𝐸𝑇 .

𝐸𝑇 ⊆ 𝐸 Flat . Take any 𝑒 ∈ 𝐸𝑇 . Then 𝑒 ∈ 𝑉𝑟0 and |𝑒 ∩ 𝑈𝑖 | ≤ 1 for all 𝑖, so 𝑒 uses vertices from exactly 𝑟 distinct
parts. Since 𝑘 ≥ 𝑟 + 1, there exists an index 𝑗 ∈ {1, . . . , 𝑘 } such that 𝑒 ∩ 𝑈 𝑗 = ∅. Choose any vertex 𝑥 ∈ 𝑈 𝑗
and set 𝑆 := 𝑒 ∪ {𝑥}. Then |𝑆| = 𝑟 + 1 and still |𝑆 ∩ 𝑈𝑖 | ≤ 1 for all 𝑖, hence 𝑞 := 𝜄𝑛 (𝑆) ∈ 𝐸 (𝑛) . Moreover
𝜋(𝜕 (𝑞)) = 𝜋(𝑞) = 𝑆, so
  

𝑆
𝜋(𝜕 (𝑞))
𝑒∈
=
⊆ 𝐸 Flat .
𝑟
𝑟
Thus 𝐸𝑇 ⊆ 𝐸 Flat .
Combining the two inclusions yields 𝐸 Flat = 𝐸𝑇 , i.e. Flat(T𝑟 (𝑛) (𝑁, 𝑘, 𝑟)) = 𝑇𝑟 (𝑁, 𝑘, 𝑟).
152

□

#p152
#p153

154.

Chapter 4. Some Particular SuperHyperGraphs 4.43 Book SuperHyperGraph Book graph is a graph of 𝑝 triangles sharing one common edge, with 𝑝 additional vertices each adjacent to both endpoints [727, 728]. Book hypergraph is a 3-uniform hypergraph whose hyperedges are {𝑠0 , 𝑠1 , 𝑤 𝑖 }, so all pages share the spine {𝑠0 , 𝑠1 } (cf. [729]). Book superhypergraph is an 𝑛-superhypergraph whose superhyperedges are lifted triples { 𝑠ˆ0 , 𝑠ˆ1 , 𝑤ˆ 𝑖 }, flattening to the book hypergraph. The relevant definitions and related notions are presented below. Definition 4.43.1 (Triangular book graph). Let 𝑝 ∈ Z ≥1 . The 𝑝-page triangular book graph (briefly, the book graph) is the simple graph 𝐵 𝑝 := (𝑉 (𝐵 𝑝 ), 𝐸 (𝐵 𝑝 )) defined by 𝑉 (𝐵 𝑝 ) := {𝑠0 , 𝑠1 } ∪ {𝑤 1 , . . . , 𝑤 𝑝 }, and 𝐸 (𝐵 𝑝 ) := {𝑠0 , 𝑠1 } ∪ {𝑠0 , 𝑤 𝑖 }, {𝑠1 , 𝑤 𝑖 } : 1 ≤ 𝑖 ≤ 𝑝 . Equivalently, 𝐵 𝑝 𝐾1,1, 𝑝 , and for each 𝑖 the triple {𝑠0 , 𝑠1 , 𝑤 𝑖 } induces a triangle, with all 𝑝 triangles sharing the common edge {𝑠0 , 𝑠1 } (the spine). Definition 4.43.2 (Shadow (2-section) graph of a hypergraph). Let 𝐻 = (𝑉, 𝐸) be a hypergraph, where 𝐸 is a family of nonempty subsets of 𝑉. The shadow graph (or 2-section) of 𝐻 is the graph 𝜕 (𝐻) := (𝑉, 𝐸 𝜕 ) where 𝐸 𝜕 := {𝑥, 𝑦} ⊆ 𝑉 : 𝑥 ≠ 𝑦 and ∃𝑒 ∈ 𝐸 with {𝑥, 𝑦} ⊆ 𝑒 . Definition 4.43.3 (Book hypergraph). Let 𝑝 ∈ Z ≥1 . The 𝑝-page book hypergraph is the 3-uniform hypergraph B 𝑝 := (𝑉 (B 𝑝 ), 𝐸 (B 𝑝 )) defined by 𝐸 (B 𝑝 ) := {𝑠0 , 𝑠1 , 𝑤 𝑖 } : 1 ≤ 𝑖 ≤ 𝑝 . 𝑉 (B 𝑝 ) := {𝑠0 , 𝑠1 } ∪ {𝑤 1 , . . . , 𝑤 𝑝 }, Each hyperedge {𝑠0 , 𝑠1 , 𝑤 𝑖 } is called a page and the pair {𝑠0 , 𝑠1 } is the spine. Theorem 4.43.4 (Book hypergraph is a hypergraph). For every 𝑝 ≥ 1, B 𝑝 is a hypergraph. Proof. By definition, 𝑉 (B 𝑝 ) is a nonempty set. For each 𝑖 ∈ {1, . . . , 𝑝}, the set 𝑒 𝑖 := {𝑠0 , 𝑠1 , 𝑤 𝑖 } satisfies 𝑒 𝑖 ⊆ 𝑉 (B 𝑝 ), 𝑒 𝑖 ≠ ∅. Hence 𝐸 (B 𝑝 ) = {𝑒 𝑖 : 1 ≤ 𝑖 ≤ 𝑝} is a family of nonempty subsets of 𝑉 (B 𝑝 ), so B 𝑝 = (𝑉 (B 𝑝 ), 𝐸 (B 𝑝 )) is a hypergraph. □ Theorem 4.43.5 (Book hypergraph generalizes the book graph). For every 𝑝 ≥ 1, the shadow graph of the book hypergraph equals the book graph: 𝜕 (B 𝑝 ) = 𝐵 𝑝 . Proof. Let 𝑉 := 𝑉 (B 𝑝 ) = 𝑉 (𝐵 𝑝 ) = {𝑠0 , 𝑠1 } ∪ {𝑤 1 , . . . , 𝑤 𝑝 }. First, we prove 𝐸 (𝐵 𝑝 ) ⊆ 𝐸 𝜕 , where 𝐸 𝜕 := 𝐸 (𝜕 (B 𝑝 )). Take an arbitrary edge of 𝐵 𝑝 . (i) If the edge is {𝑠0 , 𝑠1 }, then for any 𝑖 we have {𝑠0 , 𝑠1 } ⊆ {𝑠0 , 𝑠1 , 𝑤 𝑖 } ∈ 𝐸 (B 𝑝 ), so {𝑠0 , 𝑠1 } ∈ 𝐸 𝜕 . (ii) If the edge is {𝑠0 , 𝑤 𝑖 } for some 𝑖, then {𝑠0 , 𝑤 𝑖 } ⊆ {𝑠0 , 𝑠1 , 𝑤 𝑖 } ∈ 𝐸 (B 𝑝 ), so {𝑠0 , 𝑤 𝑖 } ∈ 𝐸 𝜕 . (iii) If the edge is {𝑠1 , 𝑤 𝑖 } for some 𝑖, similarly {𝑠1 , 𝑤 𝑖 } ⊆ {𝑠0 , 𝑠1 , 𝑤 𝑖 } ∈ 𝐸 (B 𝑝 ), hence {𝑠1 , 𝑤 𝑖 } ∈ 𝐸 𝜕 . Thus every edge of 𝐵 𝑝 is an edge of 𝜕 (B 𝑝 ), so 𝐸 (𝐵 𝑝 ) ⊆ 𝐸 𝜕 . 153

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155.

Chapter 4. Some Particular SuperHyperGraphs Second, we prove 𝐸 𝜕 ⊆ 𝐸 (𝐵 𝑝 ). Let {𝑥, 𝑦} ∈ 𝐸 𝜕 . Then there exists 𝑖 with {𝑥, 𝑦} ⊆ {𝑠0 , 𝑠1 , 𝑤 𝑖 }. Hence {𝑥, 𝑦} is one of the three pairs {𝑠0 , 𝑠1 }, {𝑠0 , 𝑤 𝑖 }, {𝑠1 , 𝑤 𝑖 }, all of which belong to 𝐸 (𝐵 𝑝 ) by definition. Therefore 𝐸 𝜕 ⊆ 𝐸 (𝐵 𝑝 ). Combining both inclusions yields 𝐸 𝜕 = 𝐸 (𝐵 𝑝 ), and the vertex sets coincide, so 𝜕 (B 𝑝 ) = 𝐵 𝑝 . □ Definition 4.43.6 (Singleton embeddings and vertex lifting). For each 𝑘 ≥ 0, define the singleton embedding 𝜄 𝑘 : P 𝑘 (𝑉) → P 𝑘+1 (𝑉), 𝜄 𝑘 (𝑥) := {𝑥}. For 𝑛 ≥ 1 and 𝑣 ∈ 𝑉, define the (𝑛 − 1)-lift of 𝑣 by b 𝑣 (𝑛−1) := (𝜄𝑛−2 ◦ · · · ◦ 𝜄0 ) (𝑣) ∈ P 𝑛−1 (𝑉), with the convention b 𝑣 (0) = 𝑣 when 𝑛 = 1. Definition 4.43.7 (Book 𝑛-superhypergraph). Fix 𝑝 ≥ 1 and 𝑛 ≥ 1. Let 𝑉 := {𝑠0 , 𝑠1 } ∪ {𝑤 1 , . . . , 𝑤 𝑝 }. The 𝑝-page book 𝑛-superhypergraph is (𝑛) B (𝑛) 𝑝 := (𝑉, E 𝑝 ) where o n E 𝑝(𝑛) := 𝑒 𝑖(𝑛) : 1 ≤ 𝑖 ≤ 𝑝 , n o 𝑒 𝑖(𝑛) := 𝑠b0 (𝑛−1) , 𝑠b1 (𝑛−1) , 𝑤 c𝑖 (𝑛−1) . Thus each 𝑒 𝑖(𝑛) is a 3-element subset of P 𝑛−1 (𝑉), hence an element of P 𝑛 (𝑉). Example 4.43.8 (A concrete 2-page book 2-superhypergraph). Let 𝑝 = 2 and 𝑛 = 2. Set 𝑉 := {𝑠0 , 𝑠1 , 𝑤 1 , 𝑤 2 }. Recall that for 𝑛 = 2 we have (𝑛 − 1) = 1, so b 𝑥 (1) = {𝑥} ∈ P (𝑉) (𝑥 ∈ 𝑉). Hence the 2-page book 2-superhypergraph B2(2) = (𝑉, E2(2) ) has superhyperedge family E2(2) = {𝑒 1(2) , 𝑒 2(2) }, where, explicitly, n o 𝑒 1(2) = {𝑠0 }, {𝑠1 }, {𝑤 1 } ∈ P 2 (𝑉), n o 𝑒 2(2) = {𝑠0 }, {𝑠1 }, {𝑤 2 } ∈ P 2 (𝑉). Thus B2(2) consists of two “pages” (the two superhyperedges) sharing the common spine {{𝑠0 }, {𝑠1 }}, and differing by the third supervertex {𝑤 1 } versus {𝑤 2 }. Theorem 4.43.9 (Book 𝑛-superhypergraph is an 𝑛-SuperHyperGraph). For every 𝑝 ≥ 1 and 𝑛 ≥ 1, B (𝑛) 𝑝 is an 𝑛-SuperHyperGraph. Proof. Let 𝑉 = {𝑠0 , 𝑠1 } ∪ {𝑤 1 , . . . , 𝑤 𝑝 }. For each 𝑖, we have 𝑠b0 (𝑛−1) , 𝑠b1 (𝑛−1) , 𝑤 c𝑖 (𝑛−1) ∈ P 𝑛−1 (𝑉), so 𝑒 𝑖(𝑛) = { 𝑠b0 (𝑛−1) , 𝑠b1 (𝑛−1) , 𝑤 c𝑖 (𝑛−1) } ⊆ P 𝑛−1 (𝑉), 𝑒 𝑖(𝑛) ≠ ∅. Hence 𝑒 𝑖(𝑛) ∈ P (P 𝑛−1 (𝑉)) = P 𝑛 (𝑉) and 𝑒 𝑖(𝑛) ≠ ∅. Therefore E 𝑝(𝑛) ⊆ P 𝑛 (𝑉) \ {∅}, (𝑛) so B (𝑛) 𝑝 = (𝑉, E 𝑝 ) is an 𝑛-SuperHyperGraph by definition. 154 □

156.

[beta]

Chapter 4. Some Particular SuperHyperGraphs
Definition 4.43.10 (Flattening on lifted vertices). Let 𝑛 ≥ 1 and let 𝑉 be fixed. Define the flattening map on
lifted vertices by

♭𝑛−1 : {b
𝑣 (𝑛−1) : 𝑣 ∈ 𝑉 } → 𝑉,
♭𝑛−1 b
𝑣 (𝑛−1) := 𝑣.
Extend it to 𝑒 ⊆ {b
𝑣 (𝑛−1) : 𝑣 ∈ 𝑉 } by
♭𝑛 (𝑒) := {♭𝑛−1 (𝑥) : 𝑥 ∈ 𝑒} ⊆ 𝑉 .
Theorem 4.43.11 (Book 𝑛-superhypergraph generalizes the book graph). For every 𝑝 ≥ 1 and 𝑛 ≥ 1, if we
flatten B (𝑛)
𝑝 level-by-level, we recover the book hypergraph, and hence the book graph:

𝑉, {♭𝑛 (𝑒) : 𝑒 ∈ E 𝑝(𝑛) } = B 𝑝 ,

and thus



𝜕 𝑉, {♭𝑛 (𝑒) : 𝑒 ∈ E 𝑝(𝑛) } = 𝐵 𝑝 .

Proof. Fix 𝑖 ∈ {1, . . . , 𝑝}. By definition,
𝑒 𝑖(𝑛) = { 𝑠b0 (𝑛−1) , 𝑠b1 (𝑛−1) , 𝑤
c𝑖 (𝑛−1) }.
Applying ♭𝑛 gives

♭𝑛 𝑒 𝑖(𝑛) = {♭𝑛−1 ( 𝑠b0 (𝑛−1) ), ♭𝑛−1 ( 𝑠b1 (𝑛−1) ), ♭𝑛−1 (c
𝑤 𝑖 (𝑛−1) )} = {𝑠0 , 𝑠1 , 𝑤 𝑖 }.
Therefore

{♭𝑛 (𝑒) : 𝑒 ∈ E 𝑝(𝑛) } = {𝑠0 , 𝑠1 , 𝑤 𝑖 } : 1 ≤ 𝑖 ≤ 𝑝 = 𝐸 (B 𝑝 ).
Hence the flattened hypergraph equals B 𝑝 .
By the previous theorem “Book hypergraph generalizes the book graph”, we already proved 𝜕 (B 𝑝 ) = 𝐵 𝑝 .
Substituting B 𝑝 by the flattened hypergraph yields the desired identity.
□

4.44

Pancake SuperHyperGraph

The pancake graph is a Cayley graph [730] on 𝔖𝑛 where edges connect permutations differing by one prefix
reversal [731, 732]. The pancake hypergraph is the 2-uniform hypergraph on 𝔖𝑛 whose hyperedges are exactly
prefix-reversal pairs of permutations. The pancake 𝑛-SuperHyperGraph is a level-𝑛 superhypergraph lifting 𝔖𝑛
to 𝑛-supervertices, whose flattening recovers pancake hyperedges. The relevant definitions and related notions
are presented below.
Definition 4.44.1 (Prefix reversal on 𝔖𝑛 ). Fix an integer 𝑛 ≥ 2. For each 𝑘 ∈ {2, 3, . . . , 𝑛} and each permutation
𝜋 ∈ 𝔖𝑛 , define 𝜌 𝑘 (𝜋) ∈ 𝔖𝑛 by
(
𝜋(𝑘 + 1 − 𝑖), 1 ≤ 𝑖 ≤ 𝑘,
𝜌 𝑘 (𝜋)(𝑖) :=
𝜋(𝑖),
𝑘 < 𝑖 ≤ 𝑛.
Equivalently, in one-line notation 𝜋 = (𝜋1 𝜋2 · · · 𝜋 𝑛 ),
𝜌 𝑘 (𝜋) = (𝜋 𝑘 𝜋 𝑘−1 · · · 𝜋1 𝜋 𝑘+1 · · · 𝜋 𝑛 ).
Definition 4.44.2 (Pancake graph). [731, 732] For 𝑛 ≥ 2, the pancake graph 𝑃𝑛 is the graph
n
o
𝑃𝑛 = (𝔖𝑛 , 𝐸 (𝑃𝑛 )),
𝐸 (𝑃𝑛 ) := {𝜋, 𝜌 𝑘 (𝜋)} 𝜋 ∈ 𝔖𝑛 , 2 ≤ 𝑘 ≤ 𝑛 .
Definition 4.44.3 (Pancake hypergraph). For 𝑛 ≥ 2, the pancake hypergraph H𝑛 is the 2-uniform hypergraph
H𝑛 = (𝔖𝑛 , 𝐸 (H𝑛 )),

𝐸 (H𝑛 ) := 𝐸 (𝑃𝑛 ).

(Thus every hyperedge has size 2, and H𝑛 encodes exactly the same adjacencies as 𝑃𝑛 .)
155

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157.

Chapter 4. Some Particular SuperHyperGraphs Example 4.44.4 (A concrete pancake hypergraph on 𝔖3 ). A hypergraph is a pair 𝐻 = (𝑉, 𝐸) where 𝑉 is a finite set and 𝐸 ⊆ P (𝑉) \ {∅}. Let 𝑉 := 𝔖3 , written in one-line notation: 𝔖3 = {[123], [132], [213], [231], [312], [321]}. For 𝑘 ∈ {2, 3}, define the prefix-reversal map 𝜌 𝑘 : 𝔖3 → 𝔖3 by 𝜌2 ( [𝑎 𝑏 𝑐]) := [𝑏 𝑎 𝑐], 𝜌3 ( [𝑎 𝑏 𝑐]) := [𝑐 𝑏 𝑎]. Define the pancake hypergraph (which is 2-uniform) by H3 := 𝔖3 , 𝐸 (H3 ) , 𝐸 (H3 ) := {𝜋, 𝜌 𝑘 (𝜋)} 𝜋 ∈ 𝔖3 , 𝑘 ∈ {2, 3} . Computing explicitly, the distinct hyperedges are 𝐸 (H3 ) = {[123], [213]}, {[123], [321]}, {[132], [231]}, {[132], [312]}, {[213], [312]}, {[231], [321]} . Thus H3 is a concrete pancake hypergraph. Definition 4.44.5 (Iterated singleton lift). Let 𝑋 be a set and 𝑥 ∈ 𝑋. Define b 𝑥 (𝑡 ) recursively by b 𝑥 (0) := 𝑥, b 𝑥 (𝑡+1) := {b 𝑥 (𝑡 ) } (𝑡 ∈ N0 ). Lemma 4.44.6. Let 𝑋 be a set and 𝑥 ∈ 𝑋. Then for every 𝑡 ∈ N0 , b 𝑥 (𝑡 ) ∈ P 𝑡 (𝑋), where P 0 (𝑋) := 𝑋 and P 𝑡+1 (𝑋) := P (P 𝑡 (𝑋)). Proof. We prove the claim by induction on 𝑡. Base case 𝑡 = 0. By definition, b 𝑥 (0) = 𝑥 ∈ 𝑋 = P 0 (𝑋). Inductive step. Assume b 𝑥 (𝑡 ) ∈ P 𝑡 (𝑋) for some 𝑡 ≥ 0. Then {b 𝑥 (𝑡 ) } ⊆ P 𝑡 (𝑋), hence b 𝑥 (𝑡+1) = {b 𝑥 (𝑡 ) } ∈ P P 𝑡 (𝑋) = P 𝑡+1 (𝑋). This completes the induction. □ Definition 4.44.7 (Pancake 𝑛-superhypergraph). Fix an integer 𝑛 ≥ 2 and let the base set be 𝑉0 := 𝔖𝑛 . Define the set of 𝑛-supervertices by n 𝑉 (𝑛) := b 𝜋 (𝑛) 𝜋 ∈ 𝔖𝑛 o ⊆ P 𝑛 (𝑉0 ). Define the set of (super)edge identifiers by 𝐸 (𝑛) := 𝔖𝑛 × {2, 3, . . . , 𝑛}. Define the incidence map 𝜕 (𝑛) : 𝐸 (𝑛) → P∗ (𝑉 (𝑛) ) by o n (𝑛) 𝜕 (𝑛) (𝜋, 𝑘) := b 𝜋 (𝑛) , 𝜌 𝑘 (𝜋) . The triple (𝑛) Span := 𝑉 (𝑛) , 𝐸 (𝑛) , 𝜕 (𝑛) is called the pancake 𝑛-superhypergraph. 156

158.

Chapter 4. Some Particular SuperHyperGraphs Example 4.44.8 (A concrete pancake 2-superhypergraph over 𝔖3 ). A level-2 superhypergraph over 𝑉0 is a triple S = (𝑉, 𝐸, 𝜕) such that 𝑉 ⊆ P 2 (𝑉0 ), 𝜕 : 𝐸 → P (𝑉) \ {∅}. 𝐸 is a finite set, Let the base set be 𝑉0 := 𝔖3 . Define iterated singleton-lifts for 𝑥 ∈ 𝑉0 by b 𝑥 (0) := 𝑥, b 𝑥 (1) := {𝑥} ∈ P (𝑉0 ), b 𝑥 (2) := {{𝑥}} ∈ P 2 (𝑉0 ). Define the set of level-2 supervertices by 𝑉 := {b 𝜋 (2) | 𝜋 ∈ 𝔖3 } ⊆ P 2 (𝔖3 ). Let the edge-identifier set be 𝐸 := 𝔖3 × {2, 3}. Using the same prefix reversals 𝜌2 , 𝜌3 as in the previous example, define the incidence map (2) 𝜕 (𝜋, 𝑘) := {b 𝜋 (2) , 𝜌 𝑘 (𝜋) } ∈ P (𝑉) \ {∅}. Then S3(2) := (𝑉, 𝐸, 𝜕) is a concrete pancake 2-superhypergraph over 𝔖3 . For instance, 𝜕 ( [123], 2) = { [123] (2) , [213] (2) } = {{[123]}}, {{[213]}} , and (2) , [321] (2) } = {{[123]}}, {{[321]}} . 𝜕 ( [123], 3) = { [123] Theorem 4.44.9 (The pancake 𝑛-superhypergraph is an 𝑛-SuperHyperGraph). For every integer 𝑛 ≥ 2, the structure (𝑛) Span = 𝑉 (𝑛) , 𝐸 (𝑛) , 𝜕 (𝑛) is a well-defined level-𝑛 SuperHyperGraph over the base set 𝑉0 = 𝔖𝑛 . Proof. We verify the defining requirements explicitly. Step 1 (𝑉 (𝑛) ⊆ P 𝑛 (𝑉0 )). Take any 𝑣 ∈ 𝑉 (𝑛) . Then 𝑣 = b 𝜋 (𝑛) for some 𝜋 ∈ 𝔖𝑛 = 𝑉0 . By Lemma 4.44.6 with 𝑋 = 𝑉0 and 𝑡 = 𝑛, b 𝜋 (𝑛) ∈ P 𝑛 (𝑉0 ). Hence 𝑉 (𝑛) ⊆ P 𝑛 (𝑉0 ). Step 2 (the incidence map lands in P∗ (𝑉 (𝑛) )). Take any (𝜋, 𝑘) ∈ 𝐸 (𝑛) = 𝔖𝑛 × {2, . . . , 𝑛}. Then 𝜋 ∈ 𝔖𝑛 and, (𝑛) by Definition 4.44.1, 𝜌 𝑘 (𝜋) ∈ 𝔖𝑛 . Therefore b 𝜋 (𝑛) ∈ 𝑉 (𝑛) and 𝜌 𝑘 (𝜋) ∈ 𝑉 (𝑛) , so n o (𝑛) 𝜕 (𝑛) (𝜋, 𝑘) = b 𝜋 (𝑛) , 𝜌 𝑘 (𝜋) ⊆ 𝑉 (𝑛) . Moreover, 𝜕 (𝑛) (𝜋, 𝑘) contains (at least) the element b 𝜋 (𝑛) , hence it is nonempty: 𝜕 (𝑛) (𝜋, 𝑘) ≠ ∅. Thus 𝜕 (𝑛) (𝜋, 𝑘) ∈ P∗ (𝑉 (𝑛) ). (𝑛) Step 3 (conclusion). Steps 1–2 show that Span satisfies the requirements of a level-𝑛 SuperHyperGraph over 𝑉0 = 𝔖𝑛 . □ 157

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#p156

159.

Chapter 4. Some Particular SuperHyperGraphs Definition 4.44.10 (Flattening map and flattening). Define 𝑓𝑛 : 𝑉 (𝑛) → 𝔖𝑛 by 𝑓𝑛 b 𝜋 (𝑛) := 𝜋. (𝑛) Define the flattening of Span to be the hypergraph (𝑛) Flat Span := 𝔖𝑛 , 𝐸 Flat , 𝐸 Flat := n 𝑓𝑛 [𝜕 (𝑛) (𝑒)] o 𝑒 ∈ 𝐸 (𝑛) , where 𝑓𝑛 [𝜕 (𝑛) (𝑒)] := { 𝑓𝑛 (𝑥) | 𝑥 ∈ 𝜕 (𝑛) (𝑒) }. Theorem 4.44.11 (Flattening recovers the pancake hypergraph (and hence the pancake graph)). For every 𝑛 ≥ 2, (𝑛) Flat Span = H𝑛 . (𝑛) Consequently, viewing each 2-element hyperedge of Flat(Span ) as a graph edge yields exactly 𝑃𝑛 . Proof. Let 𝑒 = (𝜋, 𝑘) ∈ 𝐸 (𝑛) = 𝔖𝑛 × {2, . . . , 𝑛} be arbitrary. By Definition 4.44.7, n o (𝑛) 𝜕 (𝑛) (𝑒) = 𝜕 (𝑛) (𝜋, 𝑘) = b 𝜋 (𝑛) , 𝜌 𝑘 (𝜋) . Apply 𝑓𝑛 (b 𝜎 (𝑛) ) = 𝜎 to obtain n o (𝑛) 𝑓𝑛 [𝜕 (𝑛) (𝜋, 𝑘)] = 𝑓𝑛 (b 𝜋 (𝑛) ), 𝑓𝑛 ( 𝜌 𝑘 (𝜋) ) = {𝜋, 𝜌 𝑘 (𝜋)}. Therefore n 𝐸 Flat = {𝜋, 𝜌 𝑘 (𝜋)} o 𝜋 ∈ 𝔖𝑛 , 2 ≤ 𝑘 ≤ 𝑛 = 𝐸 (H𝑛 ) (𝑛) ) = H𝑛 . by Definition 4.44.3. Since the vertex sets are both 𝔖𝑛 , we have Flat(Span Finally, H𝑛 is 2-uniform, so interpreting each hyperedge {𝜋, 𝜌 𝑘 (𝜋)} as an edge produces precisely the pancake graph 𝑃𝑛 from Definition 4.44.2. □ 4.45 Connected 𝑛-SuperHyperGraph A connected graph has a path between every two vertices, so the whole vertex set forms one component [733]. Related notions include Fuzzy Connected Graphs [734], Biconnected Graphs [735], and MultiConnected Graphs [736]. A connected hypergraph has a Berge path between any two vertices, alternating vertices and hyperedges containing consecutive vertices [737,738]. A connected 𝑛-superhypergraph has a super-Berge path between any two supervertices, alternating supervertices and superedges via incidence. The relevant definitions and related notions are presented below. Definition 4.45.1 (Connected graph). [733] Let 𝐺 = (𝑉, 𝐸) be a finite undirected graph. A (vertex-)path in 𝐺 from 𝑢 to 𝑣 is a sequence of vertices 𝑢 = 𝑣0, 𝑣1, . . . , 𝑣ℓ = 𝑣 such that {𝑣 𝑖−1 , 𝑣 𝑖 } ∈ 𝐸 for every 𝑖 = 1, . . . , ℓ. The graph 𝐺 is called connected if for every two vertices 𝑢, 𝑣 ∈ 𝑉 there exists a path in 𝐺 from 𝑢 to 𝑣. Definition 4.45.2 (Connected hypergraph (Berge connectivity)). [737, 738] Let 𝐻 = (𝑉, 𝐸) be a finite hypergraph, i.e., 𝑉 ≠ ∅, 𝐸 ⊆ P (𝑉) \ {∅}. A Berge path in 𝐻 from 𝑢 to 𝑣 is an alternating sequence 𝑢 = 𝑣 0 , 𝑒1 , 𝑣 1 , 𝑒2 , . . . , 𝑒ℓ , 𝑣 ℓ = 𝑣 such that for each 𝑖 = 1, . . . , ℓ one has 𝑣 𝑖−1 ∈ 𝑒 𝑖 and 𝑣 𝑖 ∈ 𝑒𝑖 . The hypergraph 𝐻 is called connected if for every two vertices 𝑢, 𝑣 ∈ 𝑉 there exists a Berge path from 𝑢 to 𝑣. 158

160.

[beta]

Chapter 4. Some Particular SuperHyperGraphs
Definition 4.45.3 ((Recall) Incidence graph (of a hypergraph)). Let 𝐻 = (𝑉, 𝐸) be a hypergraph. The incidence
graph (or Levi graph) of 𝐻 is the bipartite graph


𝐼 (𝐻) := 𝑉 ∪ 𝐸, 𝐹 ,
𝐹 := {𝑥, 𝑒} | 𝑥 ∈ 𝑉, 𝑒 ∈ 𝐸, 𝑥 ∈ 𝑒 .
Equivalently, 𝐻 is connected (in the Berge sense) if and only if 𝐼 (𝐻) is connected.
Definition 4.45.4 (Connected 𝑛-SuperHyperGraph). Fix a finite base set 𝑉0 and an integer 𝑛 ∈ N0 . An
𝑛-SuperHyperGraph is a triple

S = 𝑉, 𝐸, 𝜕
where 𝑉 ⊆ P 𝑛 (𝑉0 ) is a finite set of 𝑛-supervertices, 𝐸 is a finite set of superedge identifiers, and
𝜕 : 𝐸 → P (𝑉) \ {∅}
is an incidence map.
A super-Berge path in S from 𝑢 to 𝑣 (where 𝑢, 𝑣 ∈ 𝑉) is an alternating sequence
𝑢 = 𝑣 0 , 𝑒1 , 𝑣 1 , 𝑒2 , . . . , 𝑒ℓ , 𝑣 ℓ = 𝑣
such that for every 𝑖 = 1, . . . , ℓ one has
𝑣 𝑖−1 ∈ 𝜕 (𝑒 𝑖 )

𝑣 𝑖 ∈ 𝜕 (𝑒 𝑖 ).

and

The 𝑛-SuperHyperGraph S is called connected if for every two supervertices 𝑢, 𝑣 ∈ 𝑉 there exists a super-Berge
path from 𝑢 to 𝑣.
Example 4.45.5 (A connected 𝑛-SuperHyperGraph). Fix an integer 𝑛 ≥ 1 and take the base set
𝑉0 := {𝑎, 𝑏, 𝑐}.
Define the 𝑛-supervertex set by 𝑛-lifting singletons:
o
n
(𝑛)
(𝑛)
c (𝑛) ⊆ P 𝑛 (𝑉0 ),
{𝑎} , d
{𝑏} , {𝑐}
𝑉 := d

b(0) := 𝑋, 𝑋
b(𝑡+1) := { 𝑋
b(𝑡 ) }.
𝑋

Let the superedge-identifier set be
𝐸 := {𝑒 𝑎𝑏 , 𝑒 𝑏𝑐 },
and define the incidence map 𝜕 : 𝐸 → P (𝑉) \ {∅} by

(𝑛)
(𝑛)
{𝑎} , d
{𝑏}
,
𝜕 (𝑒 𝑎𝑏 ) := d


(𝑛)
c (𝑛) .
𝜕 (𝑒 𝑏𝑐 ) := d
{𝑏} , {𝑐}

Then
S := (𝑉, 𝐸, 𝜕)
is an 𝑛-SuperHyperGraph, and it is connected.
Indeed, for any two supervertices 𝑢, 𝑣 ∈ 𝑉:
(𝑛)
(𝑛)
• if {𝑢, 𝑣} = { d
{𝑎} , d
{𝑏} }, then 𝑢, 𝑒 𝑎𝑏 , 𝑣 is a super-Berge path;
(𝑛)
c (𝑛) }, then 𝑢, 𝑒 𝑏𝑐 , 𝑣 is a super-Berge path;
• if {𝑢, 𝑣} = { d
{𝑏} , {𝑐}
(𝑛)
c (𝑛) }, then
• if {𝑢, 𝑣} = { d
{𝑎} , {𝑐}
(𝑛)
(𝑛)
d
c (𝑛)
{𝑎} , 𝑒 𝑎𝑏 , d
{𝑏} , 𝑒 𝑏𝑐 , {𝑐}
(𝑛)
(𝑛)
(𝑛)
c (𝑛) ∈ 𝜕 (𝑒 𝑏𝑐 ).
is a super-Berge path because d
{𝑎} , d
{𝑏} ∈ 𝜕 (𝑒 𝑎𝑏 ) and d
{𝑏} , {𝑐}

Hence S is connected.
159

161.

Chapter 4. Some Particular SuperHyperGraphs Definition 4.45.6 ((Recall) Incidence graph (of an 𝑛-SuperHyperGraph)). Let S = (𝑉, 𝐸, 𝜕) be an 𝑛SuperHyperGraph. Its incidence graph is the bipartite graph 𝐼 (S) := 𝑉 ∪ 𝐸, 𝐹 , 𝐹 := {𝑥, 𝑒} | 𝑥 ∈ 𝑉, 𝑒 ∈ 𝐸, 𝑥 ∈ 𝜕 (𝑒) . Equivalently, S is connected (in the super-Berge sense) if and only if 𝐼 (S) is connected. Theorem 4.45.7 (Connected 𝑛-SuperHyperGraph generalizes connected hypergraph). Let 𝐻 = (𝑉, 𝐸 𝐻 ) be a (finite) hypergraph, i.e., 𝑉 ≠ ∅ and 𝐸 𝐻 ⊆ P (𝑉) \ {∅}. Define the associated 0-SuperHyperGraph S𝐻 := (𝑉, 𝐸 𝐻 , 𝜕𝐻 ), 𝜕𝐻 (𝑒) := 𝑒 (𝑒 ∈ 𝐸 𝐻 ). Then 𝐻 is connected (in the Berge sense) if and only if S𝐻 is connected (in the super-Berge sense of Definition 3.? (Connected 𝑛-SuperHyperGraph) with 𝑛 = 0). Consequently, the notion of a connected 𝑛SuperHyperGraph is a genuine extension of Berge-connectedness of hypergraphs (obtained by setting 𝑛 = 0 and 𝜕 = id). Proof. Since 𝑛 = 0, the 0-supervertex set is just the vertex set: 𝑉 ⊆ P 0 (𝑉) = 𝑉, so the supervertices of S𝐻 are exactly the vertices of 𝐻. Fix 𝑢, 𝑣 ∈ 𝑉. A Berge path in 𝐻 from 𝑢 to 𝑣 is an alternating sequence 𝑢 = 𝑣 0 , 𝑒1 , 𝑣 1 , 𝑒2 , . . . , 𝑒ℓ , 𝑣 ℓ = 𝑣 such that for each 𝑖 = 1, . . . , ℓ one has 𝑣 𝑖−1 ∈ 𝑒 𝑖 and 𝑣 𝑖 ∈ 𝑒 𝑖 . In S𝐻 , a super-Berge path from 𝑢 to 𝑣 is an alternating sequence with the same form, but the membership conditions are written using the incidence map: 𝑣 𝑖−1 ∈ 𝜕𝐻 (𝑒 𝑖 ) and 𝑣 𝑖 ∈ 𝜕𝐻 (𝑒 𝑖 ). By definition of 𝜕𝐻 (𝑒) = 𝑒, these conditions are identical to 𝑣 𝑖−1 ∈ 𝑒 𝑖 and 𝑣 𝑖 ∈ 𝑒 𝑖 . Hence, for every pair 𝑢, 𝑣 ∈ 𝑉, there exists a Berge path from 𝑢 to 𝑣 in 𝐻 if and only if there exists a super-Berge path from 𝑢 to 𝑣 in S𝐻 . Therefore 𝐻 is connected if and only if S𝐻 is connected. □ Theorem 4.45.8 (Incidence graph generalizes the hypergraph incidence (Levi) graph). Let 𝐻 = (𝑉, 𝐸 𝐻 ) be a hypergraph and let S𝐻 = (𝑉, 𝐸 𝐻 , 𝜕𝐻 ) be the associated 0-SuperHyperGraph defined in Theorem 4.45.7 with 𝜕𝐻 (𝑒) = 𝑒. Then the incidence graph of S𝐻 coincides with the incidence graph (Levi graph) of 𝐻: 𝐼 (S𝐻 ) = 𝐼 (𝐻) as bipartite graphs on the vertex set 𝑉 ∪ 𝐸 𝐻 . In particular, the construction 𝐼 (S) for 𝑛-SuperHyperGraphs extends the classical incidence graph 𝐼 (𝐻) of hypergraphs (obtained by setting 𝑛 = 0 and 𝜕 = id). Proof. By definition, the incidence graph of the hypergraph 𝐻 is 𝐼 (𝐻) = 𝑉 ∪ 𝐸 𝐻 , 𝐹𝐻 , 𝐹𝐻 := {𝑥, 𝑒} | 𝑥 ∈ 𝑉, 𝑒 ∈ 𝐸 𝐻 , 𝑥 ∈ 𝑒 . On the other hand, the incidence graph of the 0-SuperHyperGraph S𝐻 is 𝐼 (S𝐻 ) = 𝑉 ∪ 𝐸 𝐻 , 𝐹S , 𝐹S := {𝑥, 𝑒} | 𝑥 ∈ 𝑉, 𝑒 ∈ 𝐸 𝐻 , 𝑥 ∈ 𝜕𝐻 (𝑒) . Since 𝜕𝐻 (𝑒) = 𝑒 for all 𝑒 ∈ 𝐸 𝐻 , we have 𝑥 ∈ 𝜕𝐻 (𝑒) if and only if 𝑥 ∈ 𝑒. Therefore 𝐹S = 𝐹𝐻 , and the two bipartite graphs are identical: 𝐼 (S𝐻 ) = 𝐼 (𝐻). □ 160

#p161

162.

[beta]

Chapter 5

Uncertain SuperHyperGraph

In this chapter, we investigate the notion of Uncertain SuperHyperGraphs. Here, an Uncertain Set refers to
any uncertainty-handling framework such as Fuzzy Sets, Intuitionistic Fuzzy Sets, Neutrosophic Sets, and
Plithogenic Sets. Moreover, within graph theory, numerous extended concepts related to these notions have
been proposed. For additional details, the reader may consult [739, 740] as needed.
Each of graph models—fuzzy and neutrosophic—can be lifted to the hypergraph setting, giving rise to
fuzzy hypergraphs [62, 741] and neutrosophic hypergraphs [742, 743]. These ideas can be pushed further
into “recursive nested” architectures, producing fuzzy superhypergraphs and neutrosophic superhypergraphs
(see, e.g., [2, 744]). By capturing increasingly intricate and uncertain network structures, these generalized
frameworks play a vital role not only in graph theory but also across computational science, informatics,
network theory, decision science, engineering, and applied mathematics [7, 63, 112, 745]. Table 5.1, 5.2, and
5.3 presents an overview of uncertain hypergraph and superhypergraph models.
Model

Description

Membership relations

Classical Graph

A pair (𝑉, 𝐸) where 𝐸 is a set of unordered vertex pairs, representing crisp
binary adjacency.
Each vertex and edge has a fuzzy degree of presence in [0, 1], modeling
gradual adjacency.
Vertices and edges have membership
and non-membership with hesitation,
encoding partial belief in adjacency.
Vertices and edges carry truth, indeterminacy, and falsity degrees, handling
incomplete and inconsistent link information.
Membership of vertices and edges depends on attribute values and their contradiction, unifying all above graph
models.

Edge indicator 𝜒𝐸 : 𝑉 × 𝑉 → {0, 1} ⊂
[0, 1]; recovered as the {0, 1}–valued
restriction of all uncertain models.
𝜇𝑉 : 𝑉 → [0, 1], 𝜇 𝐸 : 𝐸 → [0, 1];
classical graph when 𝜇𝑉 , 𝜇 𝐸 ∈ {0, 1}.

Fuzzy Graph [61]

Intuitionistic Fuzzy Graph

Neutrosophic Graph

Plithogenic Graph

(𝜇, 𝜈) : 𝑉 ∪𝐸 → [0, 1] 2 with 𝜇+𝜈 ≤ 1;
fuzzy graph when 𝜈 = 1 − 𝜇.
(𝑇, 𝐼, 𝐹) : 𝑉 ∪ 𝐸 → [0, 1] 3 ; intuitionistic fuzzy graph when 𝑇 = 𝜇, 𝐹 =
𝜈, 𝐼 = 1 − 𝜇 − 𝜈.
𝑝𝑑𝑓 : (𝑉 ∪ 𝐸) × 𝑃𝑣 → [0, 1] 𝑠 , 𝑝𝐶𝐹 :
𝑃𝑣 × 𝑃𝑣 → [0, 1] 𝑡 ; suitable choices
give classical, fuzzy, intuitionistic, neutrosophic.

Table 5.1: Classical and uncertain Graph models with membership relations

5.1

Fuzzy 𝑛-SuperHyperGraphs

We first address the notion of Fuzzy 𝑛-SuperHyperGraphs. A fuzzy 𝑛-SuperHyperGraph is a higher-level
network representation in which supervertices and superedges carry membership values for modeling complex
interactions.
161

163.

[beta]

Chapter 5. Uncertain SuperHyperGraph
Model

Description

Membership relations

Classical Hypergraph

A pair (𝑉, 𝐸) where each hyperedge
is a nonempty subset of 𝑉, encoding
arbitrary multiway relations.
Each vertex and hyperedge is assigned a fuzzy degree in [0, 1], representing uncertain multiway connections.
Vertices and hyperedges have membership and non-membership with
hesitation, for higher-arity relations.
Vertices and hyperedges carry truth,
indeterminacy, and falsity degrees
for multiway uncertain information.
Hyperedges and vertices use
attribute-based membership and
contradiction to model multicriteria hyper-relations.

Incidence map 𝜒 : 𝐸 → {0, 1} ⊂
[0, 1]; crisp limit of all uncertain hypergraph models.
𝜇𝑉 : 𝑉 → [0, 1], 𝜇 𝐸 : 𝐸 → [0, 1];
classical hypergraph when all values
lie in {0, 1}.

Fuzzy Hypergraph

Intuitionistic Fuzzy Hypergraph

Neutrosophic Hypergraph

Plithogenic Hypergraph

(𝜇, 𝜈) : 𝑉 ∪ 𝐸 → [0, 1] 2 , 𝜇 + 𝜈 ≤ 1;
fuzzy hypergraph when 𝜈 = 1 − 𝜇.
(𝑇, 𝐼, 𝐹) : 𝑉 ∪ 𝐸 → [0, 1] 3 ; intuitionistic fuzzy hypergraph when
(𝑇, 𝐹, 𝐼) = (𝜇, 𝜈, 1 − 𝜇 − 𝜈).
𝑝𝑑𝑓 : (𝑉 ∪ 𝐸) × 𝑃𝑣 → [0, 1] 𝑠 ,
𝑝𝐶𝐹 : 𝑃𝑣 × 𝑃𝑣 → [0, 1] 𝑡 ; all previous hypergraph models obtained as
special cases.

Table 5.2: Classical and uncertain Hypergraph models with membership relations
5.1.1

Fuzzy Graph and Fuzzy HyperGraph

A fuzzy set assigns to each element a membership degree in [0, 1] [746, 747]. Fuzzy sets play a major role
in diverse domains such as control theory [748], decision-making [749], graph theory [61], topology [750],
signal processing [751], and engineering. Fuzzy graphs and fuzzy hypergraphs extend this notion by assigning
membership degrees to vertices and to (hyper)edges [61, 409, 752]. These structures have been extensively
studied, particularly for applications in decision–making and other uncertainty–driven tasks.
Definition 5.1.1 (Fuzzy Set). [746] Let 𝑋 be a nonempty universe of discourse. A fuzzy set 𝐴 on 𝑋 is specified
by a membership function
𝜇 𝐴 : 𝑋 −→ [0, 1],
where 𝜇 𝐴 (𝑥) represents the degree to which 𝑥 ∈ 𝑋 belongs to 𝐴. Equivalently, one may write
𝐴 = { (𝑥, 𝜇 𝐴 (𝑥)) | 𝑥 ∈ 𝑋 }.
A classical (crisp) subset 𝐶 ⊆ 𝑋 is recovered by restricting 𝜇 𝐴 to {0, 1}.
Definition 5.1.2 (Fuzzy graph). [61] A fuzzy graph is a triple 𝐺 = (𝑉, 𝜎, 𝜇) where 𝑉 is a finite nonempty vertex
set, 𝜎 : 𝑉 → [0, 1] assigns vertex-membership degrees, and 𝜇 : 𝑉 × 𝑉 → [0, 1] assigns edge-membership
degrees subject to
𝜇(𝑢, 𝑣) ≤ min{𝜎(𝑢), 𝜎(𝑣)}
(∀ 𝑢, 𝑣 ∈ 𝑉).
We write 𝑢𝑣 for {𝑢, 𝑣} and abbreviate 𝜇(𝑢𝑣) := 𝜇(𝑢, 𝑣). The (crisp) underlying graph of 𝐺 has vertex set 𝑉
and edge set 𝐸 ∗ := { 𝑢𝑣 : 𝜇(𝑢𝑣) > 0 }.
Example 5.1.3 (Fuzzy graph: trust network on three people). Consider a small social network of three people
𝑉 := {𝑢 1 , 𝑢 2 , 𝑢 3 },
where 𝜎(𝑢 𝑖 ) encodes how strongly each person belongs to the “core” of the group, and 𝜇(𝑢 𝑖 , 𝑢 𝑗 ) encodes the
strength of the mutual trust between 𝑢 𝑖 and 𝑢 𝑗 .
Define the vertex-membership function 𝜎 : 𝑉 → [0, 1] by
𝜎(𝑢 1 ) = 1.0,

𝜎(𝑢 2 ) = 0.8,

𝜎(𝑢 3 ) = 0.6.

Define the edge-membership function 𝜇 : 𝑉 × 𝑉 → [0, 1] (symmetric) by
𝜇(𝑢 1 , 𝑢 2 ) = 0.8,

𝜇(𝑢 2 , 𝑢 3 ) = 0.5,
162

𝜇(𝑢 1 , 𝑢 3 ) = 0.4,

164.

[beta]

Chapter 5. Uncertain SuperHyperGraph
Model

Description

Membership relations

Classical 𝑛-SuperHyperGraph

Vertices and superedges lie in
iterated powersets of a base set,
representing hierarchical multilevel relations.
Each 𝑛-supervertex and 𝑛superedge has a fuzzy membership in [0, 1] across hierarchy
levels.
Membership
and
nonmembership (with hesitation)
are assigned to 𝑛-supervertices
and 𝑛-superedges.
Each 𝑛-supervertex and 𝑛superedge has truth, indeterminacy, and falsity degrees.

Crisp incidence 𝜒 : 𝑉𝑛 ∪ 𝐸 →
{0, 1} ⊂ [0, 1]; obtained from
uncertain models by enforcing
{0, 1} values.
𝜇𝑉 : 𝑉𝑛 → [0, 1], 𝜇 𝐸 :
𝐸 → [0, 1]; classical case when
𝜇𝑉 , 𝜇 𝐸 ∈ {0, 1}.

Fuzzy 𝑛-SuperHyperGraph

Intuitionistic Fuzzy 𝑛-SuperHyperGraph

Neutrosophic 𝑛-SuperHyperGraph

Plithogenic 𝑛-SuperHyperGraph

Supervertices and superedges
use attribute-based membership
vectors and contradiction degrees, at all levels.

(𝜇, 𝜈)
:
𝑉𝑛 ∪ 𝐸
→
[0, 1] 2 , 𝜇 + 𝜈 ≤ 1; fuzzy
𝑛-SuperHyperGraph
when
𝜈 = 1 − 𝜇.
(𝑇, 𝐼, 𝐹) : 𝑉𝑛 ∪ 𝐸 → [0, 1] 3 ;
intuitionistic
fuzzy
𝑛SuperHyperGraph
when
(𝑇, 𝐹, 𝐼) = (𝜇, 𝜈, 1 − 𝜇 − 𝜈).
𝑝𝑑𝑓 : (𝑉𝑛 ∪ 𝐸) × 𝑃𝑣 → [0, 1] 𝑠 ,
𝑝𝐶𝐹 : 𝑃𝑣 × 𝑃𝑣 → [0, 1] 𝑡 ;
specializes to all previous 𝑛SuperHyperGraph models.

Table 5.3: Classical and uncertain 𝑛-SuperHyperGraph models with membership relations

and 𝜇(𝑢 𝑖 , 𝑢 𝑖 ) = 0 and 𝜇(𝑢 𝑖 , 𝑢 𝑗 ) = 0 for any unordered pair not listed above.
Then for every pair 𝑢 𝑖 , 𝑢 𝑗 ∈ 𝑉 we have
𝜇(𝑢 𝑖 , 𝑢 𝑗 ) ≤ min{𝜎(𝑢 𝑖 ), 𝜎(𝑢 𝑗 )},
for example
𝜇(𝑢 2 , 𝑢 3 ) = 0.5 ≤ min{𝜎(𝑢 2 ), 𝜎(𝑢 3 )} = min{0.8, 0.6} = 0.6.
Thus 𝐺 = (𝑉, 𝜎, 𝜇) is a fuzzy graph. The underlying crisp graph has edges 𝑢 1 𝑢 2 , 𝑢 2 𝑢 3 , 𝑢 1 𝑢 3 , forming a triangle
whose edges are equipped with fuzzy trust strengths.

As examples of extensions of fuzzy graphs, concepts such as those listed in Table 5.4 are well known.
The definition of a Fuzzy HyperGraph is presented below.
Definition 5.1.4 (Fuzzy hypergraph). (cf. [62, 773]) Let 𝐻 ∗ = (𝑉, 𝐸, 𝜕) be a crisp hypergraph. A fuzzy
hypergraph on 𝐻 ∗ is a sextuple

H = 𝑉, 𝐸, 𝜕; 𝜎, 𝜇, 𝜂 ,
with maps
𝜎 : 𝑉 → [0, 1],

𝜇 : 𝐸 → [0, 1],

𝜂 : 𝑉 × 𝐸 → [0, 1],

such that for all 𝑣 ∈ 𝑉 and 𝑒 ∈ 𝐸,
(support)



𝑣 ∈ 𝜕 (𝑒)



⇐⇒ 𝜂(𝑣, 𝑒) > 0,

(incidence bound) 𝜂(𝑣, 𝑒) ≤ min{𝜎(𝑣), 𝜇(𝑒)},
(edge–vertex bound)

𝜇(𝑒) ≤ min 𝜎(𝑢).

(5.1)
(5.2)
(5.3)

𝑢∈𝜕(𝑒)

Here 𝜎 is the vertex-membership map, 𝜇 the edge-membership map, and 𝜂 the incidence-membership map.
The underlying crisp hypergraph is (𝑉, 𝐸, 𝜕), recoverable via (5.1).
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Table 5.4: Overview of some extensions of fuzzy graphs
Type of graph
Hesitant Fuzzy Graph [753, 754]
Picture Fuzzy Graph [755, 755, 756]
Bipolar Fuzzy Graph [757, 758]
Spherical Fuzzy Graph [749, 759]
Complex Fuzzy Graph [760–762]
Interval-Valued Fuzzy Graph [763–765]
𝑚-Polar Fuzzy Graph [443, 766]
Fuzzy Soft Graph [218, 420, 767]
Fuzzy Rough Graph [768–770]
Linear Diophantine Fuzzy Graph [771, 772]

Brief description
Vertices and edges carry hesitant fuzzy sets with several
possible membership degrees.
Vertices and edges have picture fuzzy labels (positive, neutral, negative, refusal).
Each vertex and edge has both positive and negative membership degrees.
Membership, non-membership, and hesitancy degrees satisfy a spherical constraint.
Membership degrees are complex numbers encoding magnitude and phase-like information.
Vertices and edges are assigned intervals of membership
degrees instead of single values.
Each vertex and edge has an 𝑚-tuple of membership degrees
capturing multiple polar attitudes.
Combines fuzzy graphs with parameterized soft sets on vertices and edges.
Uses fuzzy lower and upper approximations on vertices and
edges.
Membership is defined via linear Diophantine fuzzy information on integer pairs.

Example 5.1.5 (Fuzzy hypergraph: project teams and participation). Let 𝑉 = {𝑣 1 , 𝑣 2 , 𝑣 3 , 𝑣 4 } be a set of
employees. Suppose there are two project teams:
𝑒 1 := {𝑣 1 , 𝑣 2 , 𝑣 3 },

𝑒 2 := {𝑣 2 , 𝑣 4 }.

Define a crisp hypergraph
𝐻 ∗ = (𝑉, 𝐸, 𝜕),

𝐸 := {𝑒 1 , 𝑒 2 },

𝜕 (𝑒 𝑖 ) := 𝑒 𝑖 .

Interpret 𝜎(𝑣) as how fully 𝑣 is assigned to the department, 𝜇(𝑒) as how firmly the project team 𝑒 is established,
and 𝜂(𝑣, 𝑒) as the degree of participation of 𝑣 in team 𝑒.
Set the vertex-membership function 𝜎 : 𝑉 → [0, 1] as
𝜎(𝑣 1 ) = 0.9,

𝜎(𝑣 2 ) = 0.8,

𝜎(𝑣 3 ) = 0.7,

𝜎(𝑣 4 ) = 0.6.

Define the edge-membership function 𝜇 : 𝐸 → [0, 1] by
𝜇(𝑒 1 ) = 0.7,

𝜇(𝑒 2 ) = 0.6.

Note that
𝜇(𝑒 1 ) = 0.7 = min{𝜎(𝑣 1 ), 𝜎(𝑣 2 ), 𝜎(𝑣 3 )},

𝜇(𝑒 2 ) = 0.6 = min{𝜎(𝑣 2 ), 𝜎(𝑣 4 )},

so the edge–vertex bound (5.3) is satisfied.
Define the incidence-membership map 𝜂 : 𝑉 × 𝐸 → [0, 1] by
𝜂(𝑣 1 , 𝑒 1 ) = 𝜂(𝑣 2 , 𝑒 1 ) = 𝜂(𝑣 3 , 𝑒 1 ) = 0.7,
𝜂(𝑣 2 , 𝑒 2 ) = 𝜂(𝑣 4 , 𝑒 2 ) = 0.6,
and set
𝜂(𝑣, 𝑒) = 0

whenever 𝑣 ∉ 𝜕 (𝑒).

Then for each 𝑣 ∈ 𝑉 and 𝑒 ∈ 𝐸 we have
𝑣 ∈ 𝜕 (𝑒) ⇐⇒ 𝜂(𝑣, 𝑒) > 0,
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and
𝜂(𝑣, 𝑒) ≤ min{𝜎(𝑣), 𝜇(𝑒)},
for instance
𝜂(𝑣 2 , 𝑒 2 ) = 0.6 ≤ min{𝜎(𝑣 2 ), 𝜇(𝑒 2 )} = min{0.8, 0.6} = 0.6.
Thus
H := (𝑉, 𝐸, 𝜕; 𝜎, 𝜇, 𝜂)
is a fuzzy hypergraph in the sense of Definition 5.1.4, modeling two fuzzy project teams with graded participation of employees.
As examples of extensions of fuzzy hypergraphs, concepts such as those listed in Table 5.5 are well known.
Table 5.5: Overview of some extensions of fuzzy hypergraphs
Type of hypergraph
Hesitant Fuzzy HyperGraph [774]
Picture Fuzzy HyperGraph [775]
Bipolar Fuzzy HyperGraph [776, 777]
Spherical Fuzzy HyperGraph
Complex Fuzzy HyperGraph [778]

Interval-Valued Fuzzy HyperGraph [773, 779]
𝑚-Polar Fuzzy HyperGraph [780, 781]
Fuzzy Soft HyperGraph [72, 782]
Fuzzy Rough HyperGraph

5.1.2

Brief description
Vertices and hyperedges carry hesitant fuzzy sets with
several possible membership degrees.
Vertices and hyperedges have picture fuzzy labels (positive, neutral, negative, refusal).
Each vertex and hyperedge has both positive and negative
membership degrees.
Membership, non-membership, and hesitancy degrees on
vertices and hyperedges satisfy a spherical constraint.
Membership degrees on vertices and hyperedges are complex numbers encoding magnitude and phase-like information.
Vertices and hyperedges are assigned intervals of membership degrees instead of single values.
Each vertex and hyperedge has an 𝑚-tuple of membership
degrees capturing multiple polar attitudes.
Combines fuzzy hypergraphs with parameterized soft sets
on vertices and hyperedges.
Uses fuzzy lower and upper approximations on vertices
and hyperedges induced by an indiscernibility or similarity
relation.

Fuzzy 𝑛-SuperHyperGraph

A fuzzy 𝑛-SuperHyperGraph is a higher-level network representation in which supervertices and superedges
carry membership values for modeling complex interactions (cf. [2, 783]).
Definition 5.1.6 (Fuzzy 𝑛-SuperHyperGraph). (cf. [2]) Let SHG (𝑛) = (𝑉, 𝐸) be an 𝑛-SuperHyperGraph. A
fuzzy 𝑛-SuperHyperGraph is a quadruple
(𝑉, 𝐸, 𝜎, 𝜇),
where 𝜎 : 𝑉 → [0, 1] and 𝜇 : 𝐸 → [0, 1] obey the admissibility constraint
𝜇(𝑒) ≤ min 𝜎(𝑣)
𝑣 ∈𝑒

for every 𝑒 ∈ 𝐸 .

Example 5.1.7 (Fuzzy 1-SuperHyperGraph: overlapping research groups). Let 𝑉0 = {𝑎, 𝑏, 𝑐} be a set of
researchers. Consider the first iterated powerset

P1 (𝑉0 ) = P (𝑉0 ) = ∅, {𝑎}, {𝑏}, {𝑐}, {𝑎, 𝑏}, {𝑎, 𝑐}, {𝑏, 𝑐}, {𝑎, 𝑏, 𝑐} .
Define two 1-supervertices
𝑣 𝐴 := {𝑎, 𝑏},

𝑣 𝐵 := {𝑏, 𝑐},

and set
𝑉 := {𝑣 𝐴, 𝑣 𝐵 } ⊆ P1 (𝑉0 ).
165

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Table 5.6: Compact comparison: fuzzy graph vs. fuzzy hypergraph vs. fuzzy 𝑛-superhypergraph.
Item
Underlying carrier

Fuzzy Graph
Finite vertex set 𝑉

Fuzzy HyperGraph
Finite 𝑉 and hyperedge set
𝐸 with incidence 𝜕 : 𝐸 →
P (𝑉) \{∅}
𝜎 : 𝑉 → [0, 1], 𝜇 : 𝐸 →
[0, 1], 𝜂 : 𝑉 × 𝐸 → [0, 1]

Membership maps

𝜎 : 𝑉 → [0, 1], 𝜇 : 𝑉 ×𝑉 →
[0, 1]

Admissibility / bounds

𝜇(𝑢, 𝑣) ≤ min{𝜎(𝑢), 𝜎(𝑣)}

𝜂(𝑣, 𝑒) ≤ min{𝜎(𝑣), 𝜇(𝑒)}
and 𝜇(𝑒) ≤ min𝑢∈𝜕(𝑒) 𝜎(𝑢)

Interaction pattern

Pairwise edges (binary)

Higher-order
hyperedges
(sets of vertices)

Typical viewpoint

Uncertain strength of pairwise relations

Uncertain multiway relations
plus graded incidence

Fuzzy 𝑛-SuperHyperGraph
Base set 𝑉0 ; supervertices
𝑉 ⊆ P 𝑛 (𝑉0 ); superedges 𝐸
with 𝜕 : 𝐸 → P (𝑉) \{∅}
𝜎 : 𝑉 → [0, 1], 𝜇 : 𝐸 →
[0, 1] (optional: incidence
degree 𝜂 : 𝑉 × 𝐸 → [0, 1])
𝜇(𝑒) ≤ min𝑣 ∈𝜕(𝑒) 𝜎(𝑣)
(and if 𝜂 used: 𝜂(𝑣, 𝑒) ≤
min{𝜎(𝑣), 𝜇(𝑒)})
Multi-level groups as vertices (nested sets) and
higher-order
superedges
among groups
Uncertain relations between
higher-level entities (clusters/teams/modules), possibly across multiple abstraction levels

Interpret 𝑣 𝐴 as the research group jointly led by 𝑎 and 𝑏, and 𝑣 𝐵 as the group jointly led by 𝑏 and 𝑐.
Let the 1-superedge set be
𝐸 := {𝑒 1 },

𝑒 1 := {𝑣 𝐴, 𝑣 𝐵 } ⊆ 𝑉,

representing a higher-level collaboration project that involves both groups 𝑣 𝐴 and 𝑣 𝐵 .
Define the vertex-membership function 𝜎 : 𝑉 → [0, 1] and superedge-membership function 𝜇 : 𝐸 → [0, 1]
by
𝜎(𝑣 𝐴) = 0.9,
𝜎(𝑣 𝐵 ) = 0.7,
𝜇(𝑒 1 ) = 0.7.
Then
𝜇(𝑒 1 ) = 0.7 ≤ min{𝜎(𝑣 𝐴), 𝜎(𝑣 𝐵 )} = min{0.9, 0.7} = 0.7,
so the admissibility constraint
𝜇(𝑒) ≤ min 𝜎(𝑣)
𝑣 ∈𝑒

(𝑒 ∈ 𝐸)

is satisfied. Therefore
(𝑉, 𝐸, 𝜎, 𝜇)
is a fuzzy 1-SuperHyperGraph, modeling two overlapping research groups (as supervertices) and their joint
collaborative project (as a superedge) with graded membership strengths.
For reference, a compact comparison of fuzzy graphs, fuzzy hypergraphs, and fuzzy 𝑛-superhypergraphs is
provided in Table 5.6.

5.2

Intuitionistic Fuzzy SuperHyperGraph

An intuitionistic fuzzy set assigns each element degrees of membership and nonmembership whose sum is at
most one, capturing hesitation [784,785]. An intuitionistic fuzzy graph equips each vertex and edge with membership and nonmembership degrees, modeling uncertain relationships and hesitant connectivity [786, 787].
An intuitionistic fuzzy hypergraph extends intuitionistic fuzzy graphs by assigning such degrees to vertices and
hyperedges representing multiway uncertain interactions [788–790]. An intuitionistic fuzzy SuperHyperGraph
labels multi-level supervertices and superedges with intuitionistic membership, nonmembership, and hesitation
degrees, capturing hierarchical uncertainty precisely (cf. [783, 791, 792]).
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Definition 5.2.1 (Intuitionistic Fuzzy Set). [793] Let 𝑋 be a nonempty universe. An intuitionistic fuzzy set (in
the sense of Atanassov) 𝐴 on 𝑋 is given by a pair of functions
𝜇 𝐴, 𝜈 𝐴 : 𝑋 −→ [0, 1],
where for every 𝑥 ∈ 𝑋,
0 ≤ 𝜇 𝐴 (𝑥) + 𝜈 𝐴 (𝑥) ≤ 1.
Here 𝜇 𝐴 (𝑥) is the degree of membership of 𝑥 in 𝐴, 𝜈 𝐴 (𝑥) is the degree of non–membership, and the hesitation
(or indeterminacy) degree is
𝜋 𝐴 (𝑥) := 1 − 𝜇 𝐴 (𝑥) − 𝜈 𝐴 (𝑥) ∈ [0, 1].
We write
𝐴 = { ⟨𝑥, 𝜇 𝐴 (𝑥), 𝜈 𝐴 (𝑥)⟩ | 𝑥 ∈ 𝑋 }.
Definition 5.2.2 (Intuitionistic Fuzzy Hypergraph). (cf. [794–796]) Let 𝑉 be a nonempty finite set of vertices.
An intuitionistic fuzzy hyperedge on 𝑉 is an ordered pair
𝐸 = (𝜇 𝐸 , 𝜈 𝐸 ),
where
𝜇 𝐸 , 𝜈 𝐸 : 𝑉 −→ [0, 1]
such that
0 ≤ 𝜇 𝐸 (𝑣) + 𝜈 𝐸 (𝑣) ≤ 1,

∀ 𝑣 ∈ 𝑉.

Its support is defined by
supp(𝐸) =



𝑣 ∈𝑉

𝜇 𝐸 (𝑣) > 0 or 𝜈 𝐸 (𝑣) < 1 .

An intuitionistic fuzzy hypergraph is a pair

𝐻 = 𝑉, E ,
where E = {𝐸 1 , . . . , 𝐸 𝑚 } is a finite family of intuitionistic fuzzy hyperedges on 𝑉 satisfying the covering
condition
𝑚
Ø
supp(𝐸 𝑗 ) = 𝑉 .
𝑗=1

The elements of 𝑉 are called vertices, and each 𝐸 𝑗 ∈ E is called an intuitionistic fuzzy hyperedge. The order
of 𝐻 is |𝑉 |, and the number of hyperedges is |E |.
Definition 5.2.3 (Intuitionistic fuzzy 𝑛-SuperHyperGraph). Let
SHG (𝑛) = (𝑉, 𝐸, 𝜕)
be an 𝑛-SuperHyperGraph, where 𝜕 : 𝐸 → P ∗ (𝑉) is the incidence map.
An intuitionistic fuzzy 𝑛-SuperHyperGraph on SHG (𝑛) is a tuple
HIF(𝑛) = (𝑉, 𝐸, 𝜕, 𝜇𝑉 , 𝜈𝑉 , 𝜇 𝐸 , 𝜈 𝐸 ),
where

• 𝜇𝑉 , 𝜈𝑉 : 𝑉 → [0, 1] are the vertex membership and vertex nonmembership functions, satisfying the
Atanassov condition
0 ≤ 𝜇𝑉 (𝑣) + 𝜈𝑉 (𝑣) ≤ 1 for all 𝑣 ∈ 𝑉 .
For each 𝑣 ∈ 𝑉 the vertex indeterminacy degree is
𝜋𝑉 (𝑣) := 1 − 𝜇𝑉 (𝑣) − 𝜈𝑉 (𝑣) ∈ [0, 1].
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Chapter 5. Uncertain SuperHyperGraph • 𝜇 𝐸 , 𝜈 𝐸 : 𝐸 × 𝑉 → [0, 1] are the edge–vertex membership and edge–vertex nonmembership functions, such that 𝜇 𝐸 (𝑒, 𝑣) = 𝜈 𝐸 (𝑒, 𝑣) = 0 whenever 𝑣 ∉ 𝜕 (𝑒), and for every 𝑒 ∈ 𝐸 and 𝑣 ∈ 𝜕 (𝑒) we have 0 ≤ 𝜇 𝐸 (𝑒, 𝑣) + 𝜈 𝐸 (𝑒, 𝑣) ≤ 1. The corresponding edge–vertex indeterminacy degree is 𝜋 𝐸 (𝑒, 𝑣) := 1 − 𝜇 𝐸 (𝑒, 𝑣) − 𝜈 𝐸 (𝑒, 𝑣) ∈ [0, 1]. • These functions satisfy the edge–vertex appurtenance constraints 𝜇 𝐸 (𝑒, 𝑣) ≤ 𝜇𝑉 (𝑣), 𝜈 𝐸 (𝑒, 𝑣) ≤ 𝜈𝑉 (𝑣), for all 𝑒 ∈ 𝐸 and all 𝑣 ∈ 𝜕 (𝑒). The structure HIF(𝑛) is called an intuitionistic fuzzy 𝑛-SuperHyperGraph on the underlying 𝑛-SuperHyperGraph SHG (𝑛) . Example 5.2.4 (Intuitionistic fuzzy 1-SuperHyperGraph: collaboration between two project teams). We model how two cross–functional project teams in a company are jointly assigned to an “AI–Analytics” initiative, with degrees of suitability, opposition, and hesitation. Step 1: Underlying 1-SuperHyperGraph. Let the base set of employees be 𝑉0 := {Alice, Bob, Carol}. At level 𝑛 = 1 the 1-supervertices are subsets of 𝑉0 : P 1 (𝑉0 ) = P (𝑉0 ). Define two project teams (subsets of employees) 𝑣 1 := {Alice, Bob}, 𝑣 2 := {Bob, Carol}, and set 𝑉 := {𝑣 1 , 𝑣 2 } ⊆ P (𝑉0 ). We consider a single 1-superedge 𝑒 AI := {𝑣 1 , 𝑣 2 }, 𝐸 := {𝑒 AI }, representing the joint “AI–Analytics” project linking the two teams. The incidence map 𝜕 : 𝐸 → P ∗ (𝑉) is defined by 𝜕 (𝑒 AI ) := {𝑣 1 , 𝑣 2 }. Thus SHG (1) := (𝑉, 𝐸, 𝜕) is a 1-SuperHyperGraph as in Definition 2.2.3. Step 2: Intuitionistic fuzzy vertex suitability. We now assign to each 1-supervertex 𝑣 ∈ 𝑉 an intuitionistic fuzzy degree of suitability for company–wide strategic projects: 𝜇𝑉 , 𝜈𝑉 : 𝑉 → [0, 1]. Let 𝜇𝑉 (𝑣 1 ) := 0.90, 𝜈𝑉 (𝑣 1 ) := 0.05, 168

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𝜇𝑉 (𝑣 2 ) := 0.70,

𝜈𝑉 (𝑣 2 ) := 0.20.

For each 𝑣 ∈ 𝑉 we have
0 ≤ 𝜇𝑉 (𝑣) + 𝜈𝑉 (𝑣) ≤ 1,
since
𝜇𝑉 (𝑣 1 ) + 𝜈𝑉 (𝑣 1 ) = 0.90 + 0.05 = 0.95 ≤ 1,
𝜇𝑉 (𝑣 2 ) + 𝜈𝑉 (𝑣 2 ) = 0.70 + 0.20 = 0.90 ≤ 1.
Hence the vertex indeterminacy degrees are
𝜋𝑉 (𝑣 1 ) := 1 − 𝜇𝑉 (𝑣 1 ) − 𝜈𝑉 (𝑣 1 ) = 0.05,
𝜋𝑉 (𝑣 2 ) := 1 − 𝜇𝑉 (𝑣 2 ) − 𝜈𝑉 (𝑣 2 ) = 0.10.
Here 𝜇𝑉 (𝑣 𝑖 ) expresses how suitable team 𝑣 𝑖 is for strategic projects, 𝜈𝑉 (𝑣 𝑖 ) how unsuitable it is perceived to
be, and 𝜋𝑉 (𝑣 𝑖 ) quantifies remaining hesitation.
Step 3: Intuitionistic fuzzy edge–vertex incidence for the AI project. We next specify intuitionistic fuzzy
appurtenance of each team to the particular joint AI project 𝑒 AI :
𝜇 𝐸 , 𝜈 𝐸 : 𝐸 × 𝑉 → [0, 1].
By definition we set
𝜇 𝐸 (𝑒 AI , 𝑣) = 𝜈 𝐸 (𝑒 AI , 𝑣) = 0

whenever 𝑣 ∉ 𝜕 (𝑒 AI ),

but here 𝜕 (𝑒 AI ) = {𝑣 1 , 𝑣 2 } so we only need to define values for (𝑒 AI , 𝑣 1 ) and (𝑒 AI , 𝑣 2 ).
Choose
𝜇 𝐸 (𝑒 AI , 𝑣 1 ) := 0.80,

𝜈 𝐸 (𝑒 AI , 𝑣 1 ) := 0.03,

𝜇 𝐸 (𝑒 AI , 𝑣 2 ) := 0.60,

𝜈 𝐸 (𝑒 AI , 𝑣 2 ) := 0.10.

Then for each incident pair (𝑒 AI , 𝑣 𝑖 ) we have
0 ≤ 𝜇 𝐸 (𝑒 AI , 𝑣 𝑖 ) + 𝜈 𝐸 (𝑒 AI , 𝑣 𝑖 ) ≤ 1,
indeed
𝜇 𝐸 (𝑒 AI , 𝑣 1 ) + 𝜈 𝐸 (𝑒 AI , 𝑣 1 ) = 0.80 + 0.03 = 0.83 ≤ 1,
𝜇 𝐸 (𝑒 AI , 𝑣 2 ) + 𝜈 𝐸 (𝑒 AI , 𝑣 2 ) = 0.60 + 0.10 = 0.70 ≤ 1.
The edge–vertex indeterminacy degrees are therefore
𝜋 𝐸 (𝑒 AI , 𝑣 1 ) := 1 − 𝜇 𝐸 (𝑒 AI , 𝑣 1 ) − 𝜈 𝐸 (𝑒 AI , 𝑣 1 ) = 0.17,
𝜋 𝐸 (𝑒 AI , 𝑣 2 ) := 1 − 𝜇 𝐸 (𝑒 AI , 𝑣 2 ) − 𝜈 𝐸 (𝑒 AI , 𝑣 2 ) = 0.30.
Finally, the edge–vertex appurtenance constraints hold:
𝜇 𝐸 (𝑒 AI , 𝑣 1 ) = 0.80 ≤ 𝜇𝑉 (𝑣 1 ) = 0.90,

𝜈 𝐸 (𝑒 AI , 𝑣 1 ) = 0.03 ≤ 𝜈𝑉 (𝑣 1 ) = 0.05,

𝜇 𝐸 (𝑒 AI , 𝑣 2 ) = 0.60 ≤ 𝜇𝑉 (𝑣 2 ) = 0.70,

𝜈 𝐸 (𝑒 AI , 𝑣 2 ) = 0.10 ≤ 𝜈𝑉 (𝑣 2 ) = 0.20.

Real-life interpretation.
• 𝑣 1 = {Alice, Bob} is a highly suitable AI–engineering team with small opposition and mild hesitation.
• 𝑣 2 = {Bob, Carol} is reasonably suitable but has larger non–membership and hesitation (e.g. less
experience).
• The superedge 𝑒 AI represents the joint AI–Analytics project; its intuitionistic fuzzy incidence values
𝜇 𝐸 , 𝜈 𝐸 , 𝜋 𝐸 reflect how strongly each team is actually committed to this specific initiative, constrained
by their overall suitability.
Thus the tuple
HIF(1) := (𝑉, 𝐸, 𝜕, 𝜇𝑉 , 𝜈𝑉 , 𝜇 𝐸 , 𝜈 𝐸 )
is an intuitionistic fuzzy 1-SuperHyperGraph in the sense of Definition 5.2.3, modeling a real-world collaborative project between two teams with graded support, opposition, and uncertainty.
169

#p168

171.

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Chapter 5. Uncertain SuperHyperGraph

5.3

Neutrosophic SuperHyperGraph

A Neutrosophic Set assigns independent truth, indeterminacy, and falsity degrees to each element, allowing
explicit modeling of incomplete, inconsistent information [797–800]. Moreover, as generalizations of the
Neutrosophic Set, concepts such as the Quadripartitioned Neutrosophic Set and the Pentapartitioned Neutrosophic Set are also well known. A Single-valued Neutrosophic 𝑛-Superhypergraph [801] is a concept that
generalizes both the Single-valued Neutrosophic graph [802–804] and the Single-valued Neutrosophic hypergraph [805, 806]. It also extends the notion of a Fuzzy 𝑛-Superhypergraph. The formal definition and a
representative example are given below(cf. [109]).
Definition 5.3.1 (Single–valued Neutrosophic Set). [64, 800] Let 𝑋 be a nonempty universe. A single–valued
neutrosophic set 𝐴 on 𝑋 is described by a triple of functions
𝑇𝐴, 𝐼 𝐴, 𝐹𝐴 : 𝑋 −→ [0, 1],
such that for every 𝑥 ∈ 𝑋,
0 ≤ 𝑇𝐴 (𝑥) + 𝐼 𝐴 (𝑥) + 𝐹𝐴 (𝑥) ≤ 3.
Here 𝑇𝐴 (𝑥), 𝐼 𝐴 (𝑥), and 𝐹𝐴 (𝑥) denote, respectively, the degrees of truth–membership, indeterminacy–membership,
and falsity–membership of 𝑥 with respect to 𝐴. We write
𝐴 = { ⟨𝑥, 𝑇𝐴 (𝑥), 𝐼 𝐴 (𝑥), 𝐹𝐴 (𝑥)⟩ | 𝑥 ∈ 𝑋 }.
A fuzzy set is recovered when 𝐼 𝐴 (𝑥) = 0 and 𝐹𝐴 (𝑥) = 1 − 𝑇𝐴 (𝑥) for all 𝑥.
Definition 5.3.2 (Single-Valued Neutrosophic Graph). [64] Let 𝐺 ∗ = (𝑉, 𝐸) be a crisp (classical) graph,
where 𝑉 is the vertex set and 𝐸 ⊆ 𝑉 × 𝑉 the edge set. A single-valued neutrosophic graph (SVNG) on 𝐺 ∗ is
defined as a pair
𝐺 = ( 𝐴, 𝐵),
where
• 𝐴 = {⟨𝑣, 𝑇𝐴 (𝑣), 𝐼 𝐴 (𝑣), 𝐹𝐴 (𝑣)⟩ : 𝑣 ∈ 𝑉 } is the single-valued neutrosophic vertex set, with
𝑇𝐴, 𝐼 𝐴, 𝐹𝐴 : 𝑉 → [0, 1],
denoting respectively the truth-membership, indeterminacy-membership, and falsity-membership functions of vertices, such that for every 𝑣 ∈ 𝑉,
0 ≤ 𝑇𝐴 (𝑣) + 𝐼 𝐴 (𝑣) + 𝐹𝐴 (𝑣) ≤ 3.
• 𝐵 = {⟨𝑢𝑣, 𝑇𝐵 (𝑢𝑣), 𝐼 𝐵 (𝑢𝑣), 𝐹𝐵 (𝑢𝑣)⟩ : 𝑢𝑣 ∈ 𝐸 } is the single-valued neutrosophic edge set, with
𝑇𝐵 , 𝐼 𝐵 , 𝐹𝐵 : 𝐸 → [0, 1],
satisfying for all 𝑢, 𝑣 ∈ 𝑉 with 𝑢𝑣 ∈ 𝐸:
𝑇𝐵 (𝑢𝑣) ≤ min{𝑇𝐴 (𝑢), 𝑇𝐴 (𝑣)},

𝐼 𝐵 (𝑢𝑣) ≤ min{𝐼 𝐴 (𝑢), 𝐼 𝐴 (𝑣)},

𝐹𝐵 (𝑢𝑣) ≥ max{𝐹𝐴 (𝑢), 𝐹𝐴 (𝑣)}.

If 𝐵 is symmetric, 𝐺 = ( 𝐴, 𝐵) is called an undirected SVNG; otherwise, it is a directed SVNG.
For reference, a compact comparison of a Fuzzy Graph and a Single-Valued Neutrosophic Graph (SVNG) is
provided in Table 5.7. As the table illustrates, neutrosophic structures handle ambiguity and uncertainty in a
more granular manner, and therefore the study of Neutrosophic Graphs is just as important as that of Fuzzy
Graphs.
In what follows, we continue the discussion by introducing the definition of a Single-Valued Neutrosophic
Hypergraph.
170

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Chapter 5. Uncertain SuperHyperGraph
Table 5.7: Compact comparison: Fuzzy Graph vs. Single-Valued Neutrosophic Graph (SVNG).
Aspect
Underlying crisp object

Fuzzy Graph
A crisp graph 𝐺 ∗ = (𝑉 , 𝐸 ) (finite, undirected in
the usual fuzzy-graph setting).

Vertex labeling

One membership degree 𝜎 : 𝑉 → [0, 1].

Edge labeling

One membership degree 𝜇 : 𝑉 × 𝑉 → [0, 1]
(often written 𝜇 (𝑢𝑣) for 𝑢𝑣 ∈ 𝐸).
For all 𝑢, 𝑣 ∈ 𝑉,

Admissibility constraints

𝜇 (𝑢, 𝑣) ≤ min{ 𝜎 (𝑢) , 𝜎 (𝑣) }.

Single-Valued Neutrosophic Graph (SVNG) [64]
A crisp graph 𝐺 ∗ = (𝑉 , 𝐸 ) (directed or undirected; undirected when the edge set 𝐵 is symmetric).
Three membership degrees 𝑇𝐴 , 𝐼 𝐴 , 𝐹𝐴 : 𝑉 →
[0, 1] (truth, indeterminacy, falsity) with 0 ≤
𝑇𝐴 (𝑣) + 𝐼 𝐴 (𝑣) + 𝐹𝐴 (𝑣) ≤ 3.
Three membership degrees 𝑇𝐵 , 𝐼𝐵 , 𝐹𝐵 : 𝐸 →
[0, 1] attached to each 𝑢𝑣 ∈ 𝐸.
For all 𝑢𝑣 ∈ 𝐸,
𝑇𝐵 (𝑢𝑣) ≤ min{𝑇𝐴 (𝑢), 𝑇𝐴 (𝑣) },

𝐼𝐵 (𝑢𝑣) ≤ min{𝐼 𝐴 (𝑢), 𝐼 𝐴 (𝑣) },

𝐹𝐵 (𝑢𝑣) ≥ max{𝐹𝐴 (𝑢), 𝐹𝐴 (𝑣) }.
Uncertainty representation
Special case relation

Typical use

Uncertainty is encoded by a single grade (degree
of membership).
–

Graded presence/strength of vertices and edges
(e.g., similarity, trust, reliability).

Uncertainty is decomposed into three independent
grades (truth/indeterminacy/falsity).
If one sets 𝐼 𝐴 ≡ 0, 𝐹𝐴 ≡ 0 and identifies 𝜎 := 𝑇𝐴
(and similarly 𝜇 := 𝑇𝐵 ), then the SVNG constraints reduce to the fuzzy-graph constraint.
Modeling truth with explicit indeterminacy and
falsity (richer uncertainty in decision models).

Definition 5.3.3 (Single-Valued Neutrosophic Hypergraph). [742, 743, 806, 807] Let 𝑉 = {𝑣 1 , . . . , 𝑣 𝑁 } be
𝑀 be a collection of non-empty neutrosophic subsets of 𝑉 such that 𝑉 =
a finite vertex set, and let {𝐸 𝑖 }𝑖=1
𝑀
Ø
supp(𝐸 𝑖 ). Each hyperedge 𝐸 𝑖 is specified by three membership functions
𝑖=1

𝑇𝐸𝑖 , 𝐼 𝐸𝑖 , 𝐹𝐸𝑖 : 𝑉 → [0, 1],
assigning to each vertex 𝑣 ∈ 𝑉 its truth, indeterminacy, and falsity degrees, respectively, and satisfying
0 ≤ 𝑇𝐸𝑖 (𝑣) + 𝐼 𝐸𝑖 (𝑣) + 𝐹𝐸𝑖 (𝑣) ≤ 3 ∀ 𝑣 ∈ 𝑉 .
We represent 𝐸 𝑖 as the set
𝐸𝑖 =



(𝑣, 𝑇𝐸𝑖 (𝑣), 𝐼 𝐸𝑖 (𝑣), 𝐹𝐸𝑖 (𝑣)) : 𝑣 ∈ 𝑉 .

The pair 𝐻 = (𝑉, {𝐸 𝑖 }) is called a single-valued neutrosophic hypergraph.
Definition 5.3.4 (Neutrosophic 𝑛-Superhypergraph). (cf. [109, 801]) Let 𝑉0 be a finite base set of vertices, and
for each integer 𝑘 ≥ 0 define
P 0 (𝑉0 ) = 𝑉0 ,

P 𝑘+1 (𝑉0 ) = P P 𝑘 (𝑉0 ) ,
where P (·) denotes the usual powerset. An 𝑛-Superhypergraph is a pair
SHG (𝑛) = (𝑉, 𝐸),

𝑉 ⊆ P 𝑛 (𝑉0 ), 𝐸 ⊆ P 𝑛 (𝑉0 ).

A Neutrosophic 𝑛-Superhypergraph is then the tuple

𝑉, 𝐸, 𝑇𝑉 , 𝐼𝑉 , 𝐹𝑉 , 𝑇𝐸 , 𝐼 𝐸 , 𝐹𝐸 ,
where
• 𝑇𝑉 , 𝐼𝑉 , 𝐹𝑉 : 𝑉 → [0, 1] assign to each 𝑛-supervertex 𝑣 ∈ 𝑉 its truth-, indeterminacy-, and falsitymembership degrees, respectively, subject to
0 ≤ 𝑇𝑉 (𝑣) + 𝐼𝑉 (𝑣) + 𝐹𝑉 (𝑣) ≤ 3,
∀𝑣 ∈ 𝑉 .
171

173.

Chapter 5. Uncertain SuperHyperGraph • 𝑇𝐸 , 𝐼 𝐸 , 𝐹𝐸 : 𝐸 ×𝑉 → [0, 1] assign to each 𝑛-superedge 𝑒 ∈ 𝐸 and vertex 𝑣 ∈ 𝑒 its truth-, indeterminacy-, and falsity-membership degrees, respectively, subject to 0 ≤ 𝑇𝐸 (𝑒, 𝑣) + 𝐼 𝐸 (𝑒, 𝑣) + 𝐹𝐸 (𝑒, 𝑣) ≤ 3, ∀𝑒 ∈ 𝐸, ∀𝑣 ∈ 𝑒. These functions satisfy the edge-appurtenance constraints: 𝑇𝐸 (𝑒, 𝑣) ≤ 𝑇𝑉 (𝑣), 𝐼 𝐸 (𝑒, 𝑣) ≤ 𝐼𝑉 (𝑣), 𝐹𝐸 (𝑒, 𝑣) ≤ 𝐹𝑉 (𝑣), ∀ 𝑒 ∈ 𝐸, ∀ 𝑣 ∈ 𝑒. Example 5.3.5 (Neutrosophic 2-Superhypergraph: uncertain adoption of program bundles). We model uncertain adoption of multi–course program bundles across two university campuses by a Neutrosophic 2Superhypergraph. Step 1: Base set and 2-supervertices. Let the base set of atomic courses be 𝑉0 := {Math101, CS101, AI201, DS201}. Then P 0 (𝑉0 ) = 𝑉0 , P 2 (𝑉0 ) = P P (𝑉0 ) . P 1 (𝑉0 ) = P (𝑉0 ), Interpret elements of P 1 (𝑉0 ) as modules (sets of courses). Define three modules 𝑀core := {Math101, CS101}, 𝑀AI := {CS101, AI201}, 𝑀DS := {AI201, DS201}, so 𝑀core , 𝑀AI , 𝑀DS ∈ P 1 (𝑉0 ). Now form program bundles as subsets of P (𝑉0 ), hence elements of P 2 (𝑉0 ): 𝑣 AI-track := {𝑀core , 𝑀AI , 𝑀DS }, 𝑣 DS-track := {𝑀core , 𝑀DS }. Both 𝑣 AI-track and 𝑣 DS-track are subsets of P (𝑉0 ), so 𝑣 AI-track , 𝑣 DS-track ∈ P P (𝑉0 ) = P 2 (𝑉0 ). Set the 2-supervertex set 𝑉 := {𝑣 AI-track , 𝑣 DS-track } ⊆ P 2 (𝑉0 ). Step 2: Underlying 2-Superhypergraph edges. We consider two campuses: • Campus A offers only the AI track bundle. • Campus B offers both AI and Data Science (DS) track bundles. Let 𝐸 := {𝑒 A , 𝑒 B }, where 𝑒 A and 𝑒 B are edge identifiers for “Campus A offering” and “Campus B offering”, respectively. We take the incidence map 𝜕 : 𝐸 → P ∗ (𝑉) to be 𝜕 (𝑒 A ) := {𝑣 AI-track }, 𝜕 (𝑒 B ) := {𝑣 AI-track , 𝑣 DS-track }. Then SHG (2) := (𝑉, 𝐸, 𝜕) is a 2-Superhypergraph in the sense of Definition 2.2.3. Step 3: Neutrosophic degrees on 2-supervertices. We now equip SHG (2) with Neutrosophic degrees (𝑇𝑉 , 𝐼𝑉 , 𝐹𝑉 ) as in Definition 5.3.4. Interpret: 172

#p12
#p172

174.

Chapter 5. Uncertain SuperHyperGraph • 𝑇𝑉 (𝑣) = degree that bundle 𝑣 is truly an institutional “core strategic program”; • 𝐼𝑉 (𝑣) = degree of indeterminacy (ongoing negotiation); • 𝐹𝑉 (𝑣) = degree that 𝑣 is rejected as strategic. Define 𝑇𝑉 (𝑣 AI-track ) := 0.90, 𝐼𝑉 (𝑣 AI-track ) := 0.05, 𝐹𝑉 (𝑣 AI-track ) := 0.05, 𝑇𝑉 (𝑣 DS-track ) := 0.70, 𝐼𝑉 (𝑣 DS-track ) := 0.20, 𝐹𝑉 (𝑣 DS-track ) := 0.10. For each 𝑣 ∈ 𝑉, 0 ≤ 𝑇𝑉 (𝑣) + 𝐼𝑉 (𝑣) + 𝐹𝑉 (𝑣) ≤ 3, indeed 𝑇𝑉 (𝑣 AI-track ) + 𝐼𝑉 (𝑣 AI-track ) + 𝐹𝑉 (𝑣 AI-track ) = 0.90 + 0.05 + 0.05 = 1, 𝑇𝑉 (𝑣 DS-track ) + 𝐼𝑉 (𝑣 DS-track ) + 𝐹𝑉 (𝑣 DS-track ) = 0.70 + 0.20 + 0.10 = 1. Step 4: Neutrosophic edge–vertex degrees. Next we define (𝑇𝐸 , 𝐼 𝐸 , 𝐹𝐸 ) : 𝐸 × 𝑉 → [0, 1]. We set these functions to 0 whenever 𝑣 ∉ 𝜕 (𝑒) and specify values only for incident pairs (𝑒, 𝑣). Campus A. Campus A strongly adopts the AI track: 𝑇𝐸 (𝑒 A , 𝑣 AI-track ) := 0.85, 𝐼 𝐸 (𝑒 A , 𝑣 AI-track ) := 0.04, 𝐹𝐸 (𝑒 A , 𝑣 AI-track ) := 0.01. Then 𝑇𝐸 (𝑒 A , 𝑣 AI-track ) + 𝐼 𝐸 (𝑒 A , 𝑣 AI-track ) + 𝐹𝐸 (𝑒 A , 𝑣 AI-track ) = 0.85 + 0.04 + 0.01 = 0.90 ≤ 3, and the appurtenance constraints hold: 𝑇𝐸 (𝑒 A , 𝑣 AI-track ) = 0.85 ≤ 𝑇𝑉 (𝑣 AI-track ) = 0.90, 𝐼 𝐸 (𝑒 A , 𝑣 AI-track ) = 0.04 ≤ 𝐼𝑉 (𝑣 AI-track ) = 0.05, 𝐹𝐸 (𝑒 A , 𝑣 AI-track ) = 0.01 ≤ 𝐹𝑉 (𝑣 AI-track ) = 0.05. For 𝑣 DS-track ∉ 𝜕 (𝑒 A ) we set 𝑇𝐸 (𝑒 A , 𝑣 DS-track ) = 𝐼 𝐸 (𝑒 A , 𝑣 DS-track ) = 𝐹𝐸 (𝑒 A , 𝑣 DS-track ) := 0. Campus B. Campus B offers both tracks but with slightly lower certainty for the DS track: 𝑇𝐸 (𝑒 B , 𝑣 AI-track ) := 0.80, 𝐼 𝐸 (𝑒 B , 𝑣 AI-track ) := 0.05, 𝐹𝐸 (𝑒 B , 𝑣 AI-track ) := 0.05, 𝑇𝐸 (𝑒 B , 𝑣 DS-track ) := 0.60, 𝐼 𝐸 (𝑒 B , 𝑣 DS-track ) := 0.15, 𝐹𝐸 (𝑒 B , 𝑣 DS-track ) := 0.05. Again, for each incident pair (𝑒 B , 𝑣), 0 ≤ 𝑇𝐸 (𝑒 B , 𝑣) + 𝐼 𝐸 (𝑒 B , 𝑣) + 𝐹𝐸 (𝑒 B , 𝑣) ≤ 3, since 0.80 + 0.05 + 0.05 = 0.90, 0.60 + 0.15 + 0.05 = 0.80. The appurtenance constraints also hold: 𝑇𝐸 (𝑒 B , 𝑣 AI-track ) = 0.80 ≤ 𝑇𝑉 (𝑣 AI-track ) = 0.90, 𝐼 𝐸 (𝑒 B , 𝑣 AI-track ) = 0.05 ≤ 𝐼𝑉 (𝑣 AI-track ) = 0.05, 𝐹𝐸 (𝑒 B , 𝑣 AI-track ) = 0.05 ≤ 𝐹𝑉 (𝑣 AI-track ) = 0.05, 𝑇𝐸 (𝑒 B , 𝑣 DS-track ) = 0.60 ≤ 𝑇𝑉 (𝑣 DS-track ) = 0.70, 𝐼 𝐸 (𝑒 B , 𝑣 DS-track ) = 0.15 ≤ 𝐼𝑉 (𝑣 DS-track ) = 0.20, 𝐹𝐸 (𝑒 B , 𝑣 DS-track ) = 0.05 ≤ 𝐹𝑉 (𝑣 DS-track ) = 0.10. Interpretation. 173

175.

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Chapter 5. Uncertain SuperHyperGraph
• Level 0 (𝑉0 ): individual courses.
• Level 1 (P 1 (𝑉0 )): course modules (core, AI, DS).
• Level 2 (P 2 (𝑉0 )): program bundles, each a finite family of modules; these are the 2-supervertices 𝑣 AI-track
and 𝑣 DS-track .
• Superedges 𝑒 A , 𝑒 B encode which bundles each campus offers. Their Neutrosophic degrees (𝑇𝐸 , 𝐼 𝐸 , 𝐹𝐸 )
describe, for each campus and bundle, the truth, indeterminacy, and falsity of the claim “this bundle is
effectively implemented here”, bounded by the campus–independent degrees (𝑇𝑉 , 𝐼𝑉 , 𝐹𝑉 ) attached to
each bundle.
Thus
𝑉, 𝐸, 𝑇𝑉 , 𝐼𝑉 , 𝐹𝑉 , 𝑇𝐸 , 𝐼 𝐸 , 𝐹𝐸



is a Neutrosophic 2-Superhypergraph, modelling real-world uncertainty about the adoption of multi–course
program bundles across two campuses.

5.4

Plithogenic SuperHyperGraph

Plithogenic set assigns multi-criteria membership vectors to elements, modulated by contradiction degrees
between attribute values and dominance levels interactions globally [808–811]. Plithogenic graph attaches
plithogenic sets to vertices and edges, modeling networks where attribute contradictions influence weighted
connectivity patterns dynamically significantly [69, 740, 812]. Plithogenic hypergraph generalizes plithogenic
graphs, assigning plithogenic memberships to hyperedges connecting arbitrary vertex subsets under contradictory attributes and uncertainties simultaneously [70]. Plithogenic SuperHyperGraph equips multi-level
supervertices and superedges with plithogenic attribute degrees, capturing hierarchical contradictions across
nested interaction structures faithfully everywhere [2, 13, 14, 16].
Definition 5.4.1 (Plithogenic Set). [808,809] Let 𝑃 be a nonempty universe of discourse, and let 𝑣 be a (fixed)
attribute whose possible values form a nonempty set 𝑃𝑣. Fix dimensions 𝑠, 𝑡 ∈ N.
A plithogenic set on (𝑃, 𝑣, 𝑃𝑣) is a quintuple
𝑃𝑆 = (𝑃, 𝑣, 𝑃𝑣, 𝑝𝑑𝑓 , 𝑝𝐶𝐹),
where
• 𝑝𝑑𝑓 : 𝑃 × 𝑃𝑣 −→ [0, 1] 𝑠 is the degree of appurtenance function (DAF); for 𝑥 ∈ 𝑃 and 𝑎 ∈ 𝑃𝑣, 𝑝𝑑𝑓 (𝑥, 𝑎)
is the (possibly vector–valued) membership degree of 𝑥 corresponding to the attribute value 𝑎;
• 𝑝𝐶𝐹 : 𝑃𝑣 × 𝑃𝑣 −→ [0, 1] 𝑡 is the degree of contradiction function (DCF), satisfying
𝑝𝐶𝐹 (𝑎, 𝑎) = 0,

𝑝𝐶𝐹 (𝑎, 𝑏) = 𝑝𝐶𝐹 (𝑏, 𝑎)

for all 𝑎, 𝑏 ∈ 𝑃𝑣.

In plithogenic theory, a (typically fixed) dominant attribute value 𝑎 ∗ ∈ 𝑃𝑣 is chosen, and set–theoretic operations
(such as union and intersection) are defined by combining the appurtenance degrees 𝑝𝑑𝑓 with the contradiction
degrees 𝑝𝐶𝐹 ( · , 𝑎 ∗ ) in order to model interaction and opposition between different attribute values.
Example 5.4.2 (Plithogenic set: smartphone choice by reliability). Let 𝑃 := {𝑝 1 , 𝑝 2 , 𝑝 3 } be three smartphone
models and let the attribute be 𝑣 = “reliability”. Take
𝑃𝑣 := {High, Medium, Low},

𝑠 = 𝑡 = 1,

and choose the dominant attribute value 𝑎 ∗ := High.
Define the degree of appurtenance function 𝑝𝑑𝑓 : 𝑃 × 𝑃𝑣 → [0, 1] by
𝑝𝑑𝑓 (𝑥, 𝑎)
𝑝1
𝑝2
𝑝3

High
0.85
0.55
0.25
174

Medium
0.20
0.45
0.40

Low
0.05
0.10
0.70

176.

Chapter 5. Uncertain SuperHyperGraph and define the degree of contradiction function 𝑝𝐶𝐹 : 𝑃𝑣 × 𝑃𝑣 → [0, 1] by 𝑝𝐶𝐹 (𝑎, 𝑎) = 0 (𝑎 ∈ 𝑃𝑣), 𝑝𝐶𝐹 (High, Medium) = 0.3, 𝑝𝐶𝐹 (High, Low) = 0.9, 𝑝𝐶𝐹 (Medium, Low) = 0.6, extended to all pairs by symmetry. Then 𝑃𝑆 := (𝑃, 𝑣, 𝑃𝑣, 𝑝𝑑𝑓 , 𝑝𝐶𝐹) is a plithogenic set on (𝑃, 𝑣, 𝑃𝑣): each 𝑝 𝑖 has a membership degree for each attribute value, and 𝑝𝐶𝐹 (·, ·) quantifies the opposition between attribute values relative to the dominant value High. Definition 5.4.3 (Plithogenic Graph). (cf. [69, 813]) Let 𝐺 = (𝑉, 𝐸) be a crisp graph where 𝑉 is the set of vertices and 𝐸 ⊆ 𝑉 × 𝑉 is the set of edges. A Plithogenic Graph 𝑃𝐺 is defined as: 𝑃𝐺 = (𝑃𝑀, 𝑃𝑁) where: 1. Plithogenic Vertex Set 𝑃𝑀 = (𝑀, 𝑙, 𝑀𝑙, 𝑎𝑑𝑓 , 𝑎𝐶 𝑓 ): • 𝑀 ⊆ 𝑉 is the set of vertices. • 𝑙 is an attribute associated with the vertices. • 𝑀𝑙 is the range of possible attribute values. • 𝑎𝑑𝑓 : 𝑀 × 𝑀𝑙 → [0, 1] 𝑠 is the Degree of Appurtenance Function (DAF) for vertices. • 𝑎𝐶 𝑓 : 𝑀𝑙 × 𝑀𝑙 → [0, 1] 𝑡 is the Degree of Contradiction Function (DCF) for vertices. 2. Plithogenic Edge Set 𝑃𝑁 = (𝑁, 𝑚, 𝑁𝑚, 𝑏𝑑𝑓 , 𝑏𝐶 𝑓 ): • 𝑁 ⊆ 𝐸 is the set of edges. • 𝑚 is an attribute associated with the edges. • 𝑁𝑚 is the range of possible attribute values. • 𝑏𝑑𝑓 : 𝑁 × 𝑁𝑚 → [0, 1] 𝑠 is the Degree of Appurtenance Function (DAF) for edges. • 𝑏𝐶 𝑓 : 𝑁𝑚 × 𝑁𝑚 → [0, 1] 𝑡 is the Degree of Contradiction Function (DCF) for edges. The Plithogenic Graph 𝑃𝐺 must satisfy the following conditions: 1. Edge Appurtenance Constraint: For all (𝑥, 𝑎), (𝑦, 𝑏) ∈ 𝑀 × 𝑀𝑙: 𝑏𝑑𝑓 ((𝑥𝑦), (𝑎, 𝑏)) ≤ min{𝑎𝑑𝑓 (𝑥, 𝑎), 𝑎𝑑𝑓 (𝑦, 𝑏)} where 𝑥𝑦 ∈ 𝑁 is an edge between vertices 𝑥 and 𝑦, and (𝑎, 𝑏) ∈ 𝑁𝑚 × 𝑁𝑚 are the corresponding attribute values. 2. Contradiction Function Constraint: For all (𝑎, 𝑏), (𝑐, 𝑑) ∈ 𝑁𝑚 × 𝑁𝑚: 𝑏𝐶 𝑓 ((𝑎, 𝑏), (𝑐, 𝑑)) ≤ min{𝑎𝐶 𝑓 (𝑎, 𝑐), 𝑎𝐶 𝑓 (𝑏, 𝑑)} 3. Reflexivity and Symmetry of Contradiction Functions: 𝑎𝐶 𝑓 (𝑎, 𝑎) = 0, 𝑎𝐶 𝑓 (𝑎, 𝑏) = 𝑎𝐶 𝑓 (𝑏, 𝑎), 𝑏𝐶 𝑓 (𝑎, 𝑎) = 0, 𝑏𝐶 𝑓 (𝑎, 𝑏) = 𝑏𝐶 𝑓 (𝑏, 𝑎), 175 ∀𝑎 ∈ 𝑀𝑙 ∀𝑎, 𝑏 ∈ 𝑀𝑙 ∀𝑎 ∈ 𝑁𝑚 ∀𝑎, 𝑏 ∈ 𝑁𝑚

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177.

Chapter 5. Uncertain SuperHyperGraph Example 5.4.4 (Plithogenic set: smartphone choice by reliability). Let 𝑃 := {𝑝 1 , 𝑝 2 , 𝑝 3 } be three smartphone models and let the attribute be 𝑣 = “reliability”. Take 𝑃𝑣 := {High, Medium, Low}, 𝑠 = 𝑡 = 1, and choose the dominant attribute value 𝑎 ∗ := High. Define the degree of appurtenance function 𝑝𝑑𝑓 : 𝑃 × 𝑃𝑣 → [0, 1] by 𝑝𝑑𝑓 (𝑥, 𝑎) 𝑝1 𝑝2 𝑝3 High 0.85 0.55 0.25 Medium 0.20 0.45 0.40 Low 0.05 0.10 0.70 and define the degree of contradiction function 𝑝𝐶𝐹 : 𝑃𝑣 × 𝑃𝑣 → [0, 1] by 𝑝𝐶𝐹 (𝑎, 𝑎) = 0 (𝑎 ∈ 𝑃𝑣), 𝑝𝐶𝐹 (High, Medium) = 0.3, 𝑝𝐶𝐹 (High, Low) = 0.9, 𝑝𝐶𝐹 (Medium, Low) = 0.6, extended to all pairs by symmetry. Then 𝑃𝑆 := (𝑃, 𝑣, 𝑃𝑣, 𝑝𝑑𝑓 , 𝑝𝐶𝐹) is a plithogenic set on (𝑃, 𝑣, 𝑃𝑣): each 𝑝 𝑖 has a membership degree for each attribute value, and 𝑝𝐶𝐹 (·, ·) quantifies the opposition between attribute values relative to the dominant value High. Definition 5.4.5 (Plithogenic Hypergraph). (cf. [70]) Let 𝑉 be a finite set of vertices and 𝐸 ⊆ P (𝑉) a family of hyperedges. A plithogenic vertex system is a tuple 𝑃𝑀 = (𝑉, ℓ, 𝑀ℓ , adf, aCf), where • ℓ is a vertex-attribute, • 𝑀ℓ is the finite set of possible attribute values, • adf : 𝑉 × 𝑀ℓ → [0, 1] 𝑠 is the degree-of-appurtenance function, • aCf : 𝑀ℓ × 𝑀ℓ → [0, 1] 𝑡 is the degree-of-contradiction function, satisfying aCf(𝑎, 𝑎) = 0 and symmetry. Similarly, a plithogenic hyperedge system is 𝑃𝑁 = (𝐸, 𝑚, 𝑁 𝑚 , bdf, bCf), with • 𝑚 an edge-attribute, • 𝑁 𝑚 its value set, • bdf : 𝐸 × 𝑁 𝑚 → [0, 1] 𝑠 the edge-appurtenance function, • bCf : 𝑁 𝑚 × 𝑁 𝑚 → [0, 1] 𝑡 the edge-contradiction function, satisfying analogous reflexivity and symmetry. The tuple 𝐻 = (𝑃𝑀, 𝑃𝑁) is called a plithogenic hypergraph if for every 𝑒 = {𝑥, 𝑦, . . . } ∈ 𝐸 and every attribute-value combination (𝑎, 𝑏, . . . ) ∈ 𝑀ℓ × 𝑁 𝑚 the following hold: bdf(𝑒, (𝑎, 𝑏, . . . )) ≤ min{adf(𝑥, 𝑎), adf(𝑦, 𝑏), . . . }, bCf(𝛼, 𝛽) ≤ min{aCf(𝛼), aCf (𝛽)}. 176

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Chapter 5. Uncertain SuperHyperGraph
Example 5.4.6 (Plithogenic hypergraph: project teams with reliability labels). Let

𝑉 := {𝑎, 𝑏, 𝑐, 𝑑},
𝐸 := {𝑎, 𝑏, 𝑐}, {𝑏, 𝑑} ⊆ P (𝑉) \ {∅}.
Take the vertex-attribute ℓ = “availability” with
𝑀ℓ := {High, Low},

𝑠 = 𝑡 = 1,

and define adf : 𝑉 × 𝑀ℓ → [0, 1] by
adf(𝑎, High) = 0.8, adf(𝑎, Low) = 0.2,

adf(𝑏, High) = 0.6, adf(𝑏, Low) = 0.4,

adf(𝑐, High) = 0.5, adf(𝑐, Low) = 0.5,

adf(𝑑, High) = 0.3, adf(𝑑, Low) = 0.7.

Let aCf satisfy aCf(𝑢, 𝑢) = 0 and aCf(High, Low) = 0.9 (symmetric).
Let the hyperedge-attribute be 𝑚 = “team stability” with
𝑁 𝑚 := {Stable, Unstable}.
Define bdf : 𝐸 × 𝑁 𝑚 → [0, 1] by
bdf ({𝑎, 𝑏, 𝑐}, Stable) = 0.5,

bdf ({𝑏, 𝑑}, Unstable) = 0.4,

and define bCf with bCf(𝑢, 𝑢) = 0 and bCf(Stable, Unstable) = 0.8 (symmetric).
For the hyperedge 𝑒 = {𝑎, 𝑏, 𝑐}, choosing the attribute-values (High, High, High) for (𝑎, 𝑏, 𝑐) gives
min{adf(𝑎, High), adf(𝑏, High), adf(𝑐, High)} = min{0.8, 0.6, 0.5} = 0.5,
hence bdf (𝑒, Stable) = 0.5 satisfies the plithogenic appurtenance bound. For 𝑒 ′ = {𝑏, 𝑑}, choosing (Low, Low)
yields
min{adf(𝑏, Low), adf(𝑑, Low)} = min{0.4, 0.7} = 0.4,
hence bdf (𝑒 ′ , Unstable) = 0.4 is admissible. Thus 𝐻 = (𝑃𝑀, 𝑃𝑁) is a plithogenic hypergraph in the sense of
the definition.
Definition 5.4.7 (Plithogenic 𝑛-SuperHyperGraph). [2] Let 𝑉0 be a finite base set and let 𝑛 ∈ N0 . Consider
an 𝑛-SuperHyperGraph over 𝑉0 in the sense of Definition 2.2.3, that is,
SHG (𝑛) = (𝑉, 𝐸, 𝜕),
where
• 𝑉 ⊆ P 𝑛 (𝑉0 ) is a finite set of 𝑛-supervertices;
• 𝐸 is a finite set of (super)edge identifiers;
• 𝜕 : 𝐸 → P∗ (𝑉) is the incidence map, so that for each 𝑒 ∈ 𝐸, the set 𝜕 (𝑒) ⊆ 𝑉 is the nonempty incidence
set of 𝑒.
Fix the same dimensions 𝑠, 𝑡 ∈ N as above.
A plithogenic vertex system on 𝑉 is a tuple

𝑃𝑀 (𝑛) = 𝑉, ℓ, 𝑀ℓ , adf (𝑛) , aCF ,
where
• ℓ is a vertex attribute;
• 𝑀ℓ is a nonempty finite set of possible attribute values for vertices;
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Chapter 5. Uncertain SuperHyperGraph
• adf (𝑛) : 𝑉 × 𝑀ℓ → [0, 1] 𝑠 is the (vertex) degree–of–appurtenance function; for 𝑣 ∈ 𝑉 and 𝑎 ∈ 𝑀ℓ ,
adf (𝑛) (𝑣, 𝑎) encodes the (possibly vector–valued) membership degree of 𝑣 having attribute value 𝑎;
• aCF : 𝑀ℓ × 𝑀ℓ → [0, 1] 𝑡 is the (vertex) degree–of–contradiction function, satisfying
aCF(𝑎, 𝑎) = 0,

aCF(𝑎, 𝑏) = aCF(𝑏, 𝑎)

for all 𝑎, 𝑏 ∈ 𝑀ℓ .

A plithogenic superedge system on 𝐸 is a tuple

𝑃𝑁 (𝑛) = 𝐸, 𝑚, 𝑁 𝑚 , bdf (𝑛) , bCF ,
where
• 𝑚 is a superedge attribute;
• 𝑁 𝑚 is a nonempty finite set of possible attribute values for superedges;
• bdf (𝑛) : 𝐸 × 𝑁 𝑚 → [0, 1] 𝑠 is the (superedge) degree–of–appurtenance function; for 𝑒 ∈ 𝐸 and 𝑢 ∈ 𝑁 𝑚 ,
bdf (𝑛) (𝑒, 𝑢) encodes the membership degree of 𝑒 having attribute value 𝑢;
• bCF : 𝑁 𝑚 × 𝑁 𝑚 → [0, 1] 𝑡 is the (superedge) degree–of–contradiction function, satisfying
bCF(𝑢, 𝑢) = 0,

bCF(𝑢, 𝑣) = bCF(𝑣, 𝑢)

for all 𝑢, 𝑣 ∈ 𝑁 𝑚 .

For each 𝑛-superedge 𝑒 ∈ 𝐸 we assume a prescribed plithogenic aggregation rule
𝛽𝑒 : 𝑀ℓ𝜕(𝑒) −→ 𝑁 𝑚 ,
which assigns to every family of vertex–attribute values
𝛼 = (𝛼𝑣 ) 𝑣 ∈𝜕(𝑒) ∈ 𝑀ℓ𝜕(𝑒)
a superedge–attribute value 𝛽𝑒 (𝛼) ∈ 𝑁 𝑚 .
The triple
Plith-SHG (𝑛) := SHG (𝑛) , 𝑃𝑀 (𝑛) , 𝑃𝑁 (𝑛)



is called a Plithogenic 𝑛-SuperHyperGraph if, for every 𝑒 ∈ 𝐸 and every family 𝛼 = (𝛼𝑣 ) 𝑣 ∈𝜕(𝑒) ∈ 𝑀ℓ𝜕(𝑒) , the
following plithogenic appurtenance–compatibility condition holds, componentwise in [0, 1] 𝑠 :


bdf (𝑛) 𝑒, 𝛽𝑒 (𝛼) ≤ min adf (𝑛) 𝑣, 𝛼𝑣 .
𝑣 ∈𝜕(𝑒)

Here the minimum is taken pointwise in R𝑠 , that is, for each coordinate 𝑗 ∈ {1, . . . , 𝑠},


bdf (𝑛) 𝑒, 𝛽𝑒 (𝛼) 𝑗 ≤ min adf (𝑛) 𝑣, 𝛼𝑣 𝑗 .
𝑣 ∈𝜕(𝑒)

We call Plith-SHG (𝑛) a Plithogenic 𝑛-SuperHyperGraph. For 𝑛 = 1 and 𝑉 ⊆ 𝑉0 , 𝐸 corresponding to nonempty
subsets of 𝑉0 , this construction reduces to a Plithogenic hypergraph, while for 𝑛 = 0 and |𝐸 | = 1 it recovers a
single plithogenic set on the vertex universe.
Example 5.4.8 (Plithogenic 2-SuperHyperGraph: nested teams and repeated joint tasks). Let the base set be
𝑉0 := {1, 2, 3, 4}.
Consider two 2-supervertices in P 2 (𝑉0 ) = P (P (𝑉0 )):

𝑣 1 := {1, 2}, {2, 3} ,


𝑣 2 := {2, 3}, {3, 4} ,

and let
𝑉 := {𝑣 1 , 𝑣 2 } ⊆ P 2 (𝑉0 ).
178

180.

[beta]

Chapter 5. Uncertain SuperHyperGraph
Let 𝐸 := {𝑒} be a singleton superedge set and define the incidence map
𝜕 (𝑒) := {𝑣 1 , 𝑣 2 } ∈ P∗ (𝑉).
Hence SHG (2) = (𝑉, 𝐸, 𝜕) is a 2-SuperHyperGraph.
Take 𝑠 = 𝑡 = 1. Let the vertex-attribute be ℓ = “reliability class” with
𝑀ℓ := {High, Low}.
Define adf (2) : 𝑉 × 𝑀ℓ → [0, 1] by
adf (2) (𝑣 1 , High) = 0.7, adf (2) (𝑣 1 , Low) = 0.3,

adf (2) (𝑣 2 , High) = 0.6, adf (2) (𝑣 2 , Low) = 0.4.

Let aCF satisfy aCF(𝑢, 𝑢) = 0 and aCF(High, Low) = 0.8 (symmetric).
Let the superedge-attribute be 𝑚 = “task criticality” with
𝑁 𝑚 := {Critical, Routine}.
Define bdf (2) : 𝐸 × 𝑁 𝑚 → [0, 1] by
bdf (2) (𝑒, Critical) = 0.6,

bdf (2) (𝑒, Routine) = 0.4.

Let bCF satisfy bCF(𝑢, 𝑢) = 0 and bCF(Critical, Routine) = 0.5 (symmetric).
Define an aggregation rule 𝛽𝑒 : 𝑀ℓ𝜕(𝑒) → 𝑁 𝑚 by
(
𝛽𝑒 (𝛼𝑣1 , 𝛼𝑣2 ) =

Critical,
Routine,

if 𝛼𝑣1 = 𝛼𝑣2 = High,
otherwise.

Now take 𝛼𝑣1 = 𝛼𝑣2 = High. Then
𝛽𝑒 (𝛼) = Critical,

min adf (2) (𝑣, 𝛼𝑣 ) = min{0.7, 0.6} = 0.6,

𝑣 ∈𝜕(𝑒)

so the required compatibility holds:

bdf (2) 𝑒, 𝛽𝑒 (𝛼) = bdf (2) (𝑒, Critical) = 0.6 ≤ 0.6.
Therefore
Plith-SHG (2) = SHG (2) , 𝑃𝑀 (2) , 𝑃𝑁 (2)



with the above data is a concrete Plithogenic 2-SuperHyperGraph.

5.5

Uncertain SuperHyperGraph

An Uncertain Set assigns to each element a degree from an uncertainty model, unifying fuzzy, intuitionistic,
neutrosophic and plithogenic frameworks [814]. An Uncertain Graph is a graph where vertices or edges carry
degrees in an uncertainty model, subsuming fuzzy, intuitionistic, neutrosophic. An Uncertain HyperGraph
assigns uncertainty-model degrees to vertices and hyperedges in a hypergraph, modeling complex higherorder connections under incomplete information. An Uncertain SuperHyperGraph equips each supervertex
and superedge in an 𝑛-SuperHyperGraph with uncertainty-model degrees, handling hierarchical uncertainty
systematically and rigorously. We first recall the notion of an Uncertain Model, which provides the membership–degree domain.
Definition 5.5.1 (Uncertain Model). [814] Let 𝑈 denote the class of all uncertain models. Each 𝑀 ∈ 𝑈 is
specified by
• a nonempty set Dom(𝑀) ⊆ [0, 1] 𝑘 of admissible degree tuples for some fixed integer 𝑘 ≥ 1;
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Chapter 5. Uncertain SuperHyperGraph
• model–specific algebraic or geometric constraints on elements of Dom(𝑀) (for example, 𝜇 + 𝜈 ≤ 1 in
the intuitionistic fuzzy case, or 𝑇 + 𝐼 + 𝐹 ≤ 3 in the neutrosophic case).
Typical examples include:
• Fuzzy model: Dom(𝑀) = [0, 1];
• Intuitionistic fuzzy model: Dom(𝑀) = {(𝜇, 𝜈) ∈ [0, 1] 2 | 𝜇 + 𝜈 ≤ 1};
• Neutrosophic model: Dom(𝑀) = {(𝑇, 𝐼, 𝐹) ∈ [0, 1] 3 | 0 ≤ 𝑇 + 𝐼 + 𝐹 ≤ 3};
• Plithogenic model, and many other extensions.
Definition 5.5.2 (Uncertain Set (U-Set)). [814] Let 𝑋 be a nonempty universe, and let 𝑀 be a fixed uncertain
model with degree–domain Dom(𝑀) ⊆ [0, 1] 𝑘 . An Uncertain Set of type 𝑀 (or U-Set for short) on 𝑋 is a pair
U = (𝑋, 𝜇 𝑀 ),
where
𝜇 𝑀 : 𝑋 −→ Dom(𝑀)
is called the uncertainty–degree function (or membership map) of U.
For 𝑥 ∈ 𝑋, the value 𝜇 𝑀 (𝑥) ∈ Dom(𝑀) encodes the degree(s) to which 𝑥 belongs to the uncertain set,
according to the model 𝑀.
Remark 5.5.3. Special cases:
• If 𝑀 is the fuzzy model and Dom(𝑀) = [0, 1], then 𝜇 𝑀 : 𝑋 → [0, 1] is a usual fuzzy membership
function and U is a fuzzy set.
• If 𝑀 is neutrosophic, then 𝜇 𝑀 (𝑥) = (𝑇 (𝑥), 𝐼 (𝑥), 𝐹 (𝑥)) gives a neutrosophic set.
• Other choices of 𝑀 recover intuitionistic fuzzy sets, picture fuzzy sets, plithogenic sets, and so on.
As noted in the remark, various generalizations are possible. For reference, Table 5.8 presents a catalogue
of uncertainty-set families (U-Sets) organized by the dimension 𝑘 of the degree-domain Dom(𝑀) ⊆ [0, 1] 𝑘
(cf. [739]).
The definitions and related concepts of Uncertain Graphs are presented below.
Definition 5.5.4 (Uncertain Graph). Let 𝐺 = (𝑉, 𝐸) be a (finite, undirected, loopless) graph and let 𝑀 be an
uncertain model with degree–domain Dom(𝑀). An Uncertain Graph of type 𝑀 is a triple
G𝑀 = (𝑉, 𝐸, 𝜇 𝑀 ),
where
𝜇 𝑀 : 𝑉 ∪ 𝐸 −→ Dom(𝑀)
assigns to each vertex 𝑣 ∈ 𝑉 and each edge 𝑒 ∈ 𝐸 an uncertainty degree 𝜇 𝑀 (𝑣) or 𝜇 𝑀 (𝑒) in Dom(𝑀).
Optionally, one may impose model–specific consistency conditions between vertex and edge degrees (for
instance, 𝜇 𝑀 (𝑒) bounded in terms of 𝜇 𝑀 (𝑢) and 𝜇 𝑀 (𝑣) for 𝑒 = {𝑢, 𝑣} in fuzzy or intuitionistic fuzzy graph
models), but these constraints are encoded in the choice of 𝑀 and are not fixed at the level of this general
definition.
Remark 5.5.5. Again, particular choices of 𝑀 recover well–known graph models:
• Fuzzy graph (when 𝑀 is fuzzy and 𝜇 𝑀 : 𝑉 ∪ 𝐸 → [0, 1]);
• Intuitionistic fuzzy graph, neutrosophic graph, plithogenic graph, etc., for the corresponding models 𝑀.
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Chapter 5. Uncertain SuperHyperGraph
Table 5.8: A catalogue of uncertainty-set families (U-Sets) by the dimension 𝑘 of the degree-domain Dom(𝑀) ⊆
[0, 1] 𝑘 [739].
𝑘
1
2

note

3

4

5
6
7
8
9
𝑛
2𝑛
3𝑛

(𝑛 ≥ 1)
(𝑛 ≥ 1)
(𝑛 ≥ 1)

Representative U-Set model(s) whose degree-domain is a subset of [0, 1] 𝑘
Fuzzy Set [62, 746]; N-Fuzzy Set [815–817] Shadowed Set [818–820]
Intuitionistic Fuzzy Set [784,821]; Vague Set [102,822]; Bipolar Fuzzy Set (two-component
description) [823]; Variable Fuzzy Set [824–826]; Paraconsistent Fuzzy Set [827, 828];
Bifuzzy Set [829, 830]
Single-Valued Neutrosophic Set [800, 831]; Picture Fuzzy Set [832, 833]; Spherical Fuzzy
Set [749, 834]; Tripolar Fuzzy Set (three-component formalisms) [835–837]; Neutrosophic
Vague Set [838, 839]
Quadripartitioned Neutrosophic Set [840,841]; Double-Valued Neutrosophic Set [842,843];
Dual Hesitant Fuzzy Set [844, 845]; Ambiguous Set [846–848]; Turiyam Neutrosophic
Set [849–852]
Pentapartitioned Neutrosophic Set [853–855]; Triple-Valued Neutrosophic Set [856–858]
Hexapartitioned Neutrosophic Set; Quadruple-Valued Neutrosophic Set [857, 859]
Heptapartitioned Neutrosophic Set; Quintuple-Valued Neutrosophic Set [857, 860, 861]
Octapartitioned Neutrosophic Set [862]
Nonapartitioned Neutrosophic Set [862]
Multi-valued (Fuzzy) Sets [863]; MultiFuzzy Set [864]; 𝑛-Refined Fuzzy Set [865, 866]
𝑛-Refined Intuitionistic Fuzzy Set [866]; Multi-Intuitionistic Fuzzy Set [864]
𝑛-Refined Neutrosophic Set [866]; Multi-Neutrosophic Set [864, 867]

Reading guide. In the U-Set scheme [814], each model 𝑀 is specified by a degree-domain Dom( 𝑀 ) ⊆ [0, 1] 𝑘 and a membership map
𝜇 𝑀 : 𝑋 → Dom( 𝑀 ). The table groups representative families by the ambient dimension 𝑘 (i.e., how many numerical components are
stored per element).
(a) A widely cited viewpoint is that neutrosophic sets provide a unifying umbrella covering several earlier multi-component fuzzy models
(and their generalizations); see [868].
(b) Ambiguous sets are commonly presented as subclasses of certain four-component neutrosophic families; see [840, 841, 848].
(c) Turiyam neutrosophic sets are reported as subclasses of quadripartitioned neutrosophic sets; see [869].

As a reference, Table 5.9 presents a catalogue of uncertainty-graph families (Uncertain Graphs) organised by
the dimension 𝑘 of the degree-domain Dom(𝑀) ⊆ [0, 1] 𝑘 .
Definition 5.5.6 (Uncertain HyperGraph). Let 𝐻 = (𝑉, 𝐸) be a hypergraph and let 𝑀 be an uncertain model
with degree–domain Dom(𝑀). An Uncertain HyperGraph of type 𝑀 is a triple
H𝑀 = (𝑉, 𝐸, 𝜇 𝑀 ),
where
𝜇 𝑀 : 𝑉 ∪ 𝐸 −→ Dom(𝑀)
assigns an uncertainty degree to each vertex 𝑣 ∈ 𝑉 and each hyperedge 𝑒 ∈ 𝐸.
As in the graph case, possible relations between vertex and hyperedge degrees (for instance, bounds of 𝜇 𝑀 (𝑒)
in terms of 𝜇 𝑀 (𝑣) for 𝑣 ∈ 𝑒) are governed by the chosen model 𝑀 and its constraints.
Remark 5.5.7. For suitable choices of 𝑀, this framework yields fuzzy hypergraphs, intuitionistic fuzzy
hypergraphs, neutrosophic hypergraphs, plithogenic hypergraphs, and many further extensions. We present
the catalogue of uncertainty-hypergraph families (Uncertain HyperGraphs) by the dimension 𝑘 of the degreedomain Dom(𝑀) ⊆ [0, 1] 𝑘 in Table 5.10.
Definition 5.5.8 (Uncertain 𝑛-SuperHyperGraph). Let 𝑉0 be a finite base set and let 𝑛 ∈ N0 . Assume that an
𝑛-SuperHyperGraph on 𝑉0 is given by
SHG (𝑛) = (𝑉𝑛 , 𝐸),
where
∅ ≠ 𝑉𝑛 ⊆ P 𝑛 (𝑉0 )

and

∅ ≠ 𝐸 ⊆ P (𝑉𝑛 ) \ {∅},

so that each 𝑛-superedge 𝑒 ∈ 𝐸 is a nonempty subset of the 𝑛-supervertex set 𝑉𝑛 .
Let 𝑀 be a fixed uncertain model with degree–domain Dom(𝑀) ⊆ [0, 1] 𝑘 . An Uncertain 𝑛-SuperHyperGraph
of type 𝑀 is a triple
(𝑛)
S𝑀
= (𝑉𝑛 , 𝐸, 𝜇 𝑀 ),
181

183.

Chapter 5. Uncertain SuperHyperGraph Table 5.9: A catalogue of uncertainty-graph families (Uncertain Graphs) by the dimension 𝑘 of the degreedomain Dom(𝑀) ⊆ [0, 1] 𝑘 . 𝑘 1 2 3 4 5 6 7 8 9 𝑛 2𝑛 3𝑛 Representative uncertainty-graph type(s) G𝑀 = (𝑉, 𝐸, 𝜇 𝑀 ) with 𝜇 𝑀 : 𝑉 ∪ 𝐸 → Dom(𝑀) ⊆ [0, 1] 𝑘 Fuzzy graph; 𝑁-graph; shadowed-graph variants Intuitionistic fuzzy graph [786]; vague graph [870]; bipolar fuzzy graph [758]; intuitionistic evidence graph; variable fuzzy graph; paraconsistent fuzzy graph; bifuzzy graph [871, 872] Neutrosophic graph [64](a) ; hesitant fuzzy graph [873]; tripolar fuzzy graph; three-way fuzzy graph; picture fuzzy graph [499, 874]; spherical fuzzy graph [749]; inconsistent intuitionistic fuzzy graph; ternary fuzzy / neutrosophic-fuzzy graph; neutrosophic vague graph Quadripartitioned neutrosophic graph [875, 876]; double-valued neutrosophic graph [842]; dual hesitant fuzzy graph [877]; ambiguous graph(b) ; local-neutrosophic graph; support-neutrosophic graph; turiyam neutrosophic graph [878](c) Pentapartitioned neutrosophic graph [879]; triple-valued neutrosophic graph Hexapartitioned neutrosophic graph; quadruple-valued neutrosophic graph Heptapartitioned neutrosophic graph [880]; quintuple-valued neutrosophic graph Octapartitioned neutrosophic graph Nonapartitioned neutrosophic graph 𝑛-refined fuzzy graph; multi-valued (fuzzy) graphs; multi-fuzzy graphs [881] 𝑛-refined intuitionistic fuzzy graph; multi-intuitionistic fuzzy graphs 𝑛-refined neutrosophic graph; multi-neutrosophic graphs (a) Neutrosophic graph models are often treated as broad frameworks that can specialize to many degree-based graph formalisms under suitable constraints. (b) Ambiguous-graph models are commonly presented as subclasses of certain quadripartitioned and also double-valued neutrosophic graph models. (c) Turiyam neutrosophic graphs are reported as subclasses of certain quadripartitioned neutrosophic graph models. Table 5.10: A catalogue of uncertainty-hypergraph families (Uncertain HyperGraphs) by the dimension 𝑘 of the degree-domain Dom(𝑀) ⊆ [0, 1] 𝑘 . 𝑘 1 2 3 4 5 𝑘 Representative uncertainty-hypergraph family (type 𝑀 with Dom(𝑀) ⊆ [0, 1] 𝑘 ) Fuzzy HyperGraph [882–884]: 𝜇 𝑀 : 𝑉 ∪ 𝐸 → [0, 1]. Intuitionistic-fuzzy HyperGraph [885–887]: 𝜇 𝑀 : 𝑉 ∪𝐸 → [0, 1] 2 (e.g., (membership, non-membership)). Neutrosophic HyperGraph [66, 67, 888, 889]: 𝜇 𝑀 : 𝑉 ∪ 𝐸 → [0, 1] 3 (e.g., (𝑇, 𝐼, 𝐹)). Quadripartitioned Neutrosophic / four-component uncertainty HyperGraph: 𝜇 𝑀 : 𝑉 ∪ 𝐸 → [0, 1] 4 . Pentapartitioned Neutrosophic / five-component uncertainty HyperGraph: 𝜇 𝑀 : 𝑉 ∪ 𝐸 → [0, 1] 5 . 𝑘-component uncertainty HyperGraph: 𝜇 𝑀 : 𝑉 ∪ 𝐸 → Dom(𝑀) ⊆ [0, 1] 𝑘 (model-specific semantics). where 𝜇 𝑀 : 𝑉𝑛 ∪ 𝐸 −→ Dom(𝑀) assigns to each 𝑛-supervertex 𝑣 ∈ 𝑉𝑛 and each 𝑛-superedge 𝑒 ∈ 𝐸 an uncertainty degree 𝜇 𝑀 (𝑣) or 𝜇 𝑀 (𝑒) in Dom(𝑀). Any additional relations between the degrees of 𝑛-superedges and the degrees of the 𝑛-supervertices they contain (for example, model- specific bounds or aggregations) are imposed by the chosen uncertain model 𝑀 and are not fixed at the level of this general definition. For 𝑛 = 0 and 𝑉0 = 𝑉𝑛 , the above notion reduces to an Uncertain HyperGraph of type 𝑀. Remark 5.5.9. Particular choices of the model 𝑀 recover well–known uncertain SuperHyperGraph types: • Fuzzy 𝑛-SuperHyperGraphs (when 𝑀 is fuzzy); • Intuitionistic fuzzy, neutrosophic, and plithogenic 𝑛-SuperHyperGraphs for the corresponding models 𝑀; • More exotic variants (e.g. 𝑞-rung orthopair, picture fuzzy, refined neutrosophic) are obtained by choosing the appropriate degree–domain Dom(𝑀). Regarding the catalogue of uncertainty-superhypergraph families (Uncertain 𝑛-SuperHyperGraphs) by the dimension 𝑘 of the degree-domain Dom(𝑀) ⊆ [0, 1] 𝑘 , we list them in Table 5.11. 182

184.

Chapter 5. Uncertain SuperHyperGraph Table 5.11: A catalogue of uncertainty-superhypergraph families (Uncertain 𝑛-SuperHyperGraphs) by the dimension 𝑘 of the degree-domain Dom(𝑀) ⊆ [0, 1] 𝑘 . 𝑘 1 2 3 4 𝑘 5.6 Representative uncertainty-superhypergraph family (type 𝑀 with Dom(𝑀) ⊆ [0, 1] 𝑘 ) Fuzzy 𝑛-SuperHyperGraph [783]: 𝜇 𝑀 : 𝑉𝑛 ∪ 𝐸 → [0, 1]. Intuitionistic-fuzzy 𝑛-SuperHyperGraph [783]: 𝜇𝑀 : 𝑉𝑛 ∪ 𝐸 → [0, 1] 2 (e.g., (membership, non-membership)). Neutrosophic 𝑛-SuperHyperGraph [68, 109, 801]: 𝜇 𝑀 : 𝑉𝑛 ∪ 𝐸 → [0, 1] 3 (e.g., (𝑇, 𝐼, 𝐹)). Quadripartitioned / four-component uncertainty 𝑛-SuperHyperGraph: 𝜇 𝑀 : 𝑉𝑛 ∪ 𝐸 → [0, 1] 4 . 𝑘-component uncertainty 𝑛-SuperHyperGraph: 𝜇 𝑀 : 𝑉𝑛 ∪ 𝐸 → Dom(𝑀) ⊆ [0, 1] 𝑘 (model-specific semantics). Functorial SuperHyperGraph A Functorial Set is a functor assigning each object a set and pushing elements along structure-preserving morphisms in a category [814]. A Functorial Graph functorially assigns each object a graph and maps graph homomorphisms along morphisms, preserving composition and identities everywhere. A Functorial HyperGraph assigns each object a hypergraph and transports hyperedges via hypergraph homomorphisms induced by morphisms, respecting categorical composition. A Functorial SuperHyperGraph associates each object with a superhypergraph and sends morphisms to homomorphisms preserving supervertices, superedges, and hierarchical structure. Definition 5.6.1 (Functorial Set). [814] Let C be a category and let 𝐹 : C −→ Set be a covariant functor. We call 𝐹 a Functorial Set on C. For each object 𝑋 ∈ Ob(C), the set 𝐹 (𝑋) is interpreted as the collection of “𝐹–sets over 𝑋”, and every element 𝑠 ∈ 𝐹 (𝑋) is an individual 𝐹–set based at 𝑋. Every morphism 𝑓 : 𝑋 → 𝑌 in C induces a pushforward 𝐹 ( 𝑓 ) : 𝐹 (𝑋) −→ 𝐹 (𝑌 ), 𝑠 ↦−→ 𝐹 ( 𝑓 ) (𝑠), and the usual functoriality conditions 𝐹 (id𝑋 ) = id𝐹 (𝑋) , 𝑓 𝐹 (𝑔 ◦ 𝑓 ) = 𝐹 (𝑔) ◦ 𝐹 ( 𝑓 ) 𝑔 hold for all composable morphisms 𝑋 − →𝑌 → − 𝑍. Definition 5.6.2 (Functorial Graph). Let Graph denote the category whose objects are finite, simple, undirected graphs 𝐺 = (𝑉, 𝐸) with 𝐸 ⊆ {𝑢, 𝑣} | 𝑢, 𝑣 ∈ 𝑉, 𝑢 ≠ 𝑣 , and whose morphisms 𝜑 : 𝐺 → 𝐺 ′ are graph homomorphisms, i.e. vertex maps 𝜑 : 𝑉 → 𝑉 ′ such that {𝑢, 𝑣} ∈ 𝐸 =⇒ {𝜑(𝑢), 𝜑(𝑣)} ∈ 𝐸 ′ . Let C be a category. A Functorial Graph on C is a covariant functor G : C −→ Graph. Equivalently, to each object 𝑋 ∈ Ob(C) it assigns a graph G(𝑋) = (𝑉𝑋 , 𝐸 𝑋 ), 183

185.

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Chapter 5. Uncertain SuperHyperGraph
and to each morphism 𝑓 : 𝑋 → 𝑌 in C it assigns a graph homomorphism
G( 𝑓 ) : G(𝑋) −→ G(𝑌 )
such that
G(id𝑋 ) = idG(𝑋) ,

G(𝑔 ◦ 𝑓 ) = G(𝑔) ◦ G( 𝑓 )

for all composable 𝑓 , 𝑔 in C.
Definition 5.6.3 (Functorial HyperGraph). Let HGraph denote the category whose objects are finite hypergraphs 𝐻 = (𝑉, 𝐸) with
𝐸 ⊆ P (𝑉) \ {∅},
and whose morphisms 𝜓 : 𝐻 → 𝐻 ′ are hypergraph homomorphisms, i.e. vertex maps 𝜓 : 𝑉 → 𝑉 ′ satisfying
∀𝑒 ∈ 𝐸 : 𝜓 [𝑒] ∈ 𝐸 ′ ,
where 𝜓 [𝑒] := {𝜓(𝑣) | 𝑣 ∈ 𝑒} is the image of the hyperedge 𝑒.
Let C be a category. A Functorial HyperGraph on C is a covariant functor
H : C −→ HGraph.
Equivalently, for each object 𝑋 ∈ Ob(C) it assigns a hypergraph
H(𝑋) = (𝑉𝑋 , 𝐸 𝑋 ),
and for each morphism 𝑓 : 𝑋 → 𝑌 a hypergraph homomorphism
H( 𝑓 ) : H(𝑋) −→ H(𝑌 ),
such that
H(id𝑋 ) = idH(𝑋) ,

H(𝑔 ◦ 𝑓 ) = H(𝑔) ◦ H( 𝑓 )

for all composable 𝑓 , 𝑔 in C.
Definition 5.6.4 (Functorial SuperHyperGraph). Fix an integer 𝑛 ≥ 1. Let SHGraph𝑛 denote the category
whose objects are finite level-𝑛 SuperHyperGraphs. Concretely, an object is a triple
SH = (𝑉0 , 𝑉, 𝐸),
where
• 𝑉0 is a finite base set;
• 𝑉 ⊆ P 𝑛 (𝑉0 ) is a nonempty set of 𝑛-supervertices;
• 𝐸 ⊆ P (𝑉) \ {∅} is a nonempty family of 𝑛-superedges, each superedge being a nonempty subset of 𝑉.
Thus the supervertices live at the 𝑛-th iterated powerset level, while the superedges are ordinary (nonempty)
subsets of the supervertex set 𝑉.
A morphism
Φ : (𝑉0 , 𝑉, 𝐸) −→ (𝑉0′ , 𝑉 ′ , 𝐸 ′ )
in SHGraph𝑛 is a superhypergraph homomorphism, i.e. a base map 𝜑0 : 𝑉0 → 𝑉0′ such that the induced map
on the 𝑛-th iterated powerset
𝜑 𝑛 := P 𝑛 (𝜑0 ) : P 𝑛 (𝑉0 ) −→ P 𝑛 (𝑉0′ )
satisfies
𝜑 𝑛 (𝑉) ⊆ 𝑉 ′

and

𝜑 𝑛 [𝑒] := {𝜑 𝑛 (𝑣) | 𝑣 ∈ 𝑒} ∈ 𝐸 ′

for all 𝑒 ∈ 𝐸 .

Let C be a category. A Functorial SuperHyperGraph of level 𝑛 on C is a covariant functor
SH : C −→ SHGraph𝑛 .
184

186.

Chapter 5. Uncertain SuperHyperGraph For each object 𝑋 ∈ Ob(C), the value SH(𝑋) = (𝑉0𝑋 , 𝑉𝑋 , 𝐸 𝑋 ) is a level-𝑛 SuperHyperGraph, and for each morphism 𝑓 : 𝑋 → 𝑌 in C, the arrow SH( 𝑓 ) : SH(𝑋) −→ SH(𝑌 ) is a superhypergraph homomorphism in the above sense, satisfying SH(id𝑋 ) = idSH(𝑋) , SH(𝑔 ◦ 𝑓 ) = SH(𝑔) ◦ SH( 𝑓 ) for all composable 𝑓 , 𝑔 in C. In particular, when 𝑛 = 0 and 𝑉 = 𝑉0 , a Functorial SuperHyperGraph reduces to a Functorial HyperGraph. The overview of Functorial Graphs, Functorial HyperGraphs, and Functorial SuperHyperGraphs is presented in Table 5.12. Table 5.12: A concise overview of Functorial Graphs, Functorial HyperGraphs, and Functorial SuperHyperGraphs. Concept Object assigned to each 𝑋 ∈ Ob(C) Morphisms / functoriality requirement Functorial Graph A graph G(𝑋) = (𝑉𝑋 , 𝐸 𝑋 ) in Graph. Each 𝑓 : 𝑋 → 𝑌 induces a graph homomorphism G( 𝑓 ) : G(𝑋) → G(𝑌 ), preserving edges. Moreover, G(id𝑋 ) = idG(𝑋) and G(𝑔 ◦ 𝑓 ) = G(𝑔) ◦ G( 𝑓 ). Functorial HyperGraph A hypergraph H(𝑋) = (𝑉𝑋 , 𝐸 𝑋 ) in HGraph with 𝐸 𝑋 ⊆ P (𝑉𝑋 ) \ {∅}. Each 𝑓 : 𝑋 → 𝑌 induces a hypergraph homomorphism H( 𝑓 ) : H(𝑋) → H(𝑌 ), sending every hyperedge 𝑒 ∈ 𝐸 𝑋 to H( 𝑓 ) [𝑒] ∈ 𝐸𝑌 . Moreover, H(id𝑋 ) = idH(𝑋) and H(𝑔 ◦ 𝑓 ) = H(𝑔) ◦ H( 𝑓 ). Functorial SuperHyperGraph (level 𝑛) A level-𝑛 SuperHyperGraph SH(𝑋) = (𝑉0𝑋 , 𝑉𝑋 , 𝐸 𝑋 ) in SHGraph𝑛 , with 𝑉𝑋 ⊆ P 𝑛 (𝑉0𝑋 ) and 𝐸 𝑋 ⊆ P (𝑉𝑋 ) \ {∅}. Each 𝑓 : 𝑋 → 𝑌 induces a superhypergraph homomorphism SH( 𝑓 ) : SH(𝑋) → SH(𝑌 ) arising from a base map 𝜑0 : 𝑉0𝑋 → 𝑉0𝑌 and its lift 𝜑 𝑛 = P 𝑛 (𝜑0 ), preserving supervertices and superedges. Moreover, SH(id𝑋 ) = idSH(𝑋) and SH(𝑔 ◦ 𝑓 ) = SH(𝑔) ◦ SH( 𝑓 ). 5.7 Soft SuperHyperGraph A soft set is a parameterized family of subsets representing approximate descriptions of objects under flexible, context-dependent attributes or conditions [890, 891]. A soft graph assigns to each parameter a subgraph, modeling uncertain relationships varying with expert choices, scenarios, or contexts over [420, 841, 892]. Fuzzy Soft Graphs [420, 893], HyperSoft Graph [894, 895], Soft Expert Graph [896], Neutrosophic Soft Graphs [897, 898], and other related concepts are also well established in the literature. A soft hypergraph maps parameters to subhypergraphs, capturing uncertain higher-order interactions among vertex groups under varying criteria, preferences, or environments [72, 805, 899, 900]. Fuzzy soft hypergraph [72, 901, 902], Neutrosophic Soft Hypergraphs [805], and other related concepts are also well established in the literature. A soft superhypergraph associates each parameter with a sub-superhypergraph, modeling multilevel uncertain connections between nested structures under requirements or viewpoints [801, 903, 904]. 185

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Chapter 5. Uncertain SuperHyperGraph
Definition 5.7.1 (Soft set [890]). Let 𝑈 be a universe of discourse and 𝐸 a set of parameters. Let 𝐴 ⊆ 𝐸 and
𝐹 : 𝐴 −→ P (𝑈)
be a mapping that assigns to each parameter 𝑒 ∈ 𝐴 a subset 𝐹 (𝑒) ⊆ 𝑈 of objects possessing the property 𝑒.
The pair (𝐹, 𝐴) is called a soft set over 𝑈 (with parameter subset 𝐴).
Definition 5.7.2 (Soft Graph). [905] Let 𝐺 ∗ = (𝑉, 𝐸) be a simple graph and 𝐴 a nonempty set of parameters.
Let 𝑆 ⊆ 𝐴 be nonempty, and let
𝐹 : 𝑆 → P (𝑉),

𝐾 : 𝑆 → P (𝐸).

The triple (𝐹, 𝐾, 𝑆) is called a soft graph over 𝐺 ∗ if, for every 𝑎 ∈ 𝑆 and every edge 𝑒 = {𝑢, 𝑣} ∈ 𝐾 (𝑎), one
has 𝑢, 𝑣 ∈ 𝐹 (𝑎). Equivalently, for each 𝑎 ∈ 𝑆, the pair
𝐺 𝑎 := (𝐹 (𝑎), 𝐾 (𝑎))
is a (crisp) subgraph of 𝐺 ∗ and is called the 𝑎-section of the soft graph.
Definition 5.7.3 (Soft Hypergraph). [899, 900] Let 𝐻 = (𝑉, 𝐸) be a hypergraph with 𝐸 ⊆ PSET(𝑉), and let
𝐶 be a nonempty set of parameters. A soft hypergraph over 𝐻 with parameters 𝐶 is a quadruple

𝐻, 𝐶, 𝐴, 𝐵 ,
where
𝐴 : 𝐶 −→ PSET(𝑉),

𝐵 : 𝐶 −→ PSET(𝐸),

and for each 𝑐 ∈ 𝐶,
𝐵(𝑐) ⊆ { 𝑒 ∈ 𝐸 | 𝑒 ⊆ 𝐴(𝑐)}.


The pair 𝐴(𝑐), 𝐵(𝑐) is called the soft subhypergraph of 𝐻 at parameter 𝑐.
Definition 5.7.4 (Soft 𝑛-SuperHyperGraph). [904] Let SHG(𝑛) = (𝑉, 𝐸) be an 𝑛-SuperHyperGraph and let
𝐶 be a nonempty set of parameters. A soft 𝑛-SuperHyperGraph (or soft SuperHyperGraph) over SHG(𝑛) with
parameter set 𝐶 consists of maps
𝐴 : 𝐶 −→ P(𝑉),

𝐵 : 𝐶 −→ P(𝐸),

such that for every parameter 𝑐 ∈ 𝐶 the pair
𝐴(𝑐), 𝐵(𝑐)



is a sub-𝑛-SuperHyperGraph of SHG(𝑛); that is,
𝐴(𝑐) ⊆ 𝑉,
𝐵(𝑐) ⊆ { 𝑒 ∈ 𝐸 | 𝑒 ⊆ 𝐴(𝑐) }.

For each 𝑐 ∈ 𝐶, the pair 𝐴(𝑐), 𝐵(𝑐) is called the soft slice (or soft sub-𝑛-SuperHyperGraph) of SHG(𝑛) at
parameter 𝑐.
Example 5.7.5 (Soft 2-SuperHyperGraph: public–transport demand scenarios). Consider a small public–transport
network.
Let the base set of stops be
𝑉0 := {𝑠1 , 𝑠2 , 𝑠3 },
where 𝑠1 is a residential stop, 𝑠2 a business–district stop, and 𝑠3 a shopping–area stop.
On the first level, take the following (crisp) routes as subsets of 𝑉0 :
𝑟 1 := {𝑠1 , 𝑠2 },

𝑟 2 := {𝑠2 , 𝑠3 }.

These are elements of 𝑃(𝑉0 ). Define two level–2 supervertices by
𝑣 𝐴 := {𝑟 1 , 𝑟 2 },
186

𝑣 𝐵 := {𝑟 2 },

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188.

Chapter 5. Uncertain SuperHyperGraph so that 𝑉 := {𝑣 𝐴, 𝑣 𝐵 } ⊆ 𝑃(𝑃(𝑉0 )) = 𝑃2 (𝑉0 ). Interpretation: 𝑣 𝐴 represents a daily commuting pattern combining both routes 𝑟 1 and 𝑟 2 , while 𝑣 𝐵 represents a shopping–oriented pattern concentrated on 𝑟 2 . Let 𝑒 1 := {𝑣 𝐴, 𝑣 𝐵 } ⊆ 𝑉, and put 𝐸 := {𝑒 1 }. Then SHG(2) := (𝑉, 𝐸) is a 2-SuperHyperGraph: the single superedge 𝑒 1 models that these two demand patterns interact (e.g. they share vehicles or drivers). Now let the parameter set be 𝐶 := {weekday, weekend}. Define 𝐴 : 𝐶 → 𝑃(𝑉), 𝐵 : 𝐶 → 𝑃(𝐸) by 𝐴(weekday) := {𝑣 𝐴, 𝑣 𝐵 }, 𝐵(weekday) := {𝑒 1 }, 𝐴(weekend) := {𝑣 𝐵 }, 𝐵(weekend) := ∅. For the weekday parameter, the soft slice 𝐴(weekday), 𝐵(weekday) = {𝑣 𝐴, 𝑣 𝐵 }, {𝑒 1 } is a sub–2-SuperHyperGraph of SHG(2) because 𝐴(weekday) ⊆ 𝑉 and 𝑒 1 ⊆ 𝐴(weekday). For the weekend parameter, the slice 𝐴(weekend), 𝐵(weekend) = {𝑣 𝐵 }, ∅ is also a sub–2-SuperHyperGraph: we keep only the shopping–oriented pattern 𝑣 𝐵 and drop the superedge (no strong interaction constraint is enforced in the weekend timetable). Thus ( 𝐴, 𝐵) defines a soft 2-SuperHyperGraph that models different service configurations for weekday and weekend demand in a small public–transport system. 5.8 Rough SuperHyperGraph A rough set represents a subset using lower and upper approximations induced by an equivalence relation modeling indiscernibility among elements [906, 907]. A rough graph describes a graph whose vertex and edge sets are approximated via equivalence classes, capturing uncertainty in connectivity [74, 768, 908, 909]. Fuzzy Rough Graphs [769, 910], Neutrosophic Rough Graphs [911], HyperSoft Rough Graphs [909], and Soft Rough Graphs [74] are also known as related concepts. A rough hypergraph extends rough sets to hypergraphs, approximating vertex and hyperedge families with lower and upper bounds under indiscernibility [167, 912]. A rough superhypergraph applies rough approximations to multilevel supervertices and superedges, using equivalence relations to bound uncertain hierarchical interactions robustly [904]. Definition 5.8.1 (Rough set [913]). Let 𝑈 be a nonempty finite set (universe) and let 𝑅 ⊆ 𝑈 × 𝑈 be an equivalence relation. For any 𝑋 ⊆ 𝑈, the lower and upper 𝑅–approximations of 𝑋 are defined by 𝑅∗ (𝑋) := { 𝑥 ∈ 𝑈 | [𝑥] 𝑅 ⊆ 𝑋 }, 𝑅 ∗ (𝑋) := { 𝑥 ∈ 𝑈 | [𝑥] 𝑅 ∩ 𝑋 ≠ ∅ }, where [𝑥] 𝑅 := { 𝑦 ∈ 𝑈 | (𝑥, 𝑦) ∈ 𝑅 } is the 𝑅–equivalence class of 𝑥. The pair 𝑅∗ (𝑋), 𝑅 ∗ (𝑋) is called the rough set determined by 𝑋 in the approximation space (𝑈, 𝑅). Definition 5.8.2 (Rough Graph). [768] Let 𝐺 = (𝑉, 𝐸) be a simple graph and let 𝑅 𝐸 be an equivalence relation on the edge set 𝐸. For any 𝑋 ⊆ 𝐸, define 𝑅 𝐸 (𝑋) = { 𝑒 ∈ 𝐸 : [𝑒] 𝑅𝐸 ⊆ 𝑋 }, 𝑅 𝐸 (𝑋) = { 𝑒 ∈ 𝐸 : [𝑒] 𝑅𝐸 ∩ 𝑋 ≠ ∅}. The pair 𝐺, 𝐺 , where 𝐺 = (𝑉, 𝑅 𝐸 (𝑋)) and 𝐺 = (𝑉, 𝑅 𝐸 (𝑋)), is called the rough graph approximation of the subedge-set 𝑋 ⊆ 𝐸. If 𝑋 is not a union of equivalence classes under 𝑅 𝐸 , then 𝐺 is said to be a rough graph with respect to 𝑅 𝐸 . 187

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Chapter 5. Uncertain SuperHyperGraph Definition 5.8.3 (Rough Hypergraph). [167] Let 𝐻 = (𝑉, 𝐸) be a hypergraph, 𝑅𝑉 an equivalence relation on 𝑉, and 𝑅 𝐸 an equivalence relation on 𝐸. For any 𝐴 ⊆ 𝑉 and 𝐷 ⊆ 𝐸, define 𝑅𝑉 ( 𝐴) = { 𝑣 ∈ 𝑉 : [𝑣] 𝑅𝑉 ⊆ 𝐴}, 𝑅𝑉 ( 𝐴) = { 𝑣 ∈ 𝑉 : [𝑣] 𝑅𝑉 ∩ 𝐴 ≠ ∅}, 𝑅 𝐸 (𝐷) = { 𝑒 ∈ 𝐸 : [𝑒] 𝑅𝐸 ⊆ 𝐷}, 𝑅 𝐸 (𝐷) = { 𝑒 ∈ 𝐸 : [𝑒] 𝑅𝐸 ∩ 𝐷 ≠ ∅}. The tuple 𝑉, 𝐸, 𝑅𝑉 , 𝑅𝑉 , 𝑅 𝐸 , 𝑅 𝐸 is called a rough hypergraph, capturing uncertainty on both vertices and hyperedges via rough set approximations. Definition 5.8.4 (Rough 𝑛-SuperHyperGraph). [904] Let SHG(𝑛) = (𝑉, 𝐸) be an 𝑛-SuperHyperGraph. Let 𝜑 be an equivalence relation on the 𝑛-supervertex set 𝑉, and let 𝜓 be an equivalence relation on the 𝑛-superedge set 𝐸. For any subset 𝑋 ⊆ 𝑉, the lower and upper 𝜑-approximations of 𝑋 are defined by 𝜑∗ (𝑋) := { 𝑣 ∈ 𝑉 | [𝑣] 𝜑 ⊆ 𝑋 }, 𝜑∗ (𝑋) := { 𝑣 ∈ 𝑉 | [𝑣] 𝜑 ∩ 𝑋 ≠ ∅ }, where [𝑣] 𝜑 := { 𝑢 ∈ 𝑉 | (𝑢, 𝑣) ∈ 𝜑 } is the 𝜑-equivalence class of 𝑣. Similarly, for any subset 𝐷 ⊆ 𝐸, the lower and upper 𝜓-approximations of 𝐷 are 𝜓∗ (𝐷) := { 𝑒 ∈ 𝐸 | [𝑒] 𝜓 ⊆ 𝐷 }, 𝜓 ∗ (𝐷) := { 𝑒 ∈ 𝐸 | [𝑒] 𝜓 ∩ 𝐷 ≠ ∅ }, where [𝑒] 𝜓 := { 𝑓 ∈ 𝐸 | ( 𝑓 , 𝑒) ∈ 𝜓 } is the 𝜓-equivalence class of 𝑒. The sextuple 𝑉, 𝐸, 𝜑∗ , 𝜑∗ , 𝜓∗ , 𝜓 ∗ is called a rough 𝑛-SuperHyperGraph (or rough SuperHyperGraph) on SHG(𝑛). It models uncertainty on the 𝑛-supervertices and 𝑛-superedges of SHG(𝑛) via the rough approximations induced by 𝜑 and 𝜓. Example 5.8.5 (Rough 2-SuperHyperGraph: city–logistics service areas). Consider a city–logistics planning problem. Let the base set of delivery addresses be 𝑉0 := {𝑎, 𝑏, 𝑐}, corresponding to three small zones in a city. On the first level, define delivery tours as 𝑡 1 := {𝑎, 𝑏}, 𝑡2 := {𝑏, 𝑐}, 𝑡3 := {𝑎, 𝑐} ∈ 𝑃(𝑉0 ). Define level–2 supervertices 𝑣 𝐴 := {𝑡1 , 𝑡2 }, 𝑣 𝐵 := {𝑡 2 , 𝑡3 }, 𝑣 𝐶 := {𝑡1 , 𝑡3 }, so that 𝑉 := {𝑣 𝐴, 𝑣 𝐵 , 𝑣 𝐶 } ⊆ 𝑃(𝑃(𝑉0 )) = 𝑃2 (𝑉0 ). Interpretation: each 𝑣 ∗ is a delivery pattern, i.e. a collection of tours serving certain combinations of zones. Let the superedges be 𝑒 1 := {𝑣 𝐴, 𝑣 𝐵 }, 𝑒 2 := {𝑣 𝐵 , 𝑣 𝐶 }, and put 𝐸 := {𝑒 1 , 𝑒 2 }. Then SHG(2) := (𝑉, 𝐸) is a 2-SuperHyperGraph: each superedge groups delivery patterns that share vehicles or depots. We now introduce roughness on both vertices and superedges to reflect imprecise information. 188

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Chapter 5. Uncertain SuperHyperGraph On 𝑉 define an equivalence relation 𝜑 by the classes [𝑣 𝐴] 𝜑 := {𝑣 𝐴 }, [𝑣 𝐵 ] 𝜑 := [𝑣 𝐶 ] 𝜑 := {𝑣 𝐵 , 𝑣 𝐶 }. Intuitively, 𝑣 𝐴 is a central delivery pattern, while 𝑣 𝐵 and 𝑣 𝐶 are grouped together as peripheral/mixed patterns: in coarse data, they are indistinguishable. On 𝐸 define an equivalence relation 𝜓 by the single class [𝑒 1 ] 𝜓 := [𝑒 2 ] 𝜓 := {𝑒 1 , 𝑒 2 }, meaning the two superedges are regarded as one coarse type of evening delivery coordination. Consider the subset 𝑋 := {𝑣 𝐵 } ⊆ 𝑉, representing “delivery patterns believed to mainly serve the peripheral zones.” The 𝜑–approximations of 𝑋 are 𝜑∗ (𝑋) = { 𝑣 ∈ 𝑉 | [𝑣] 𝜑 ⊆ 𝑋 } = ∅, because none of the equivalence classes is entirely contained in 𝑋, and 𝜑∗ (𝑋) = { 𝑣 ∈ 𝑉 | [𝑣] 𝜑 ∩ 𝑋 ≠ ∅ } = {𝑣 𝐵 , 𝑣 𝐶 }. Thus, only the rough upper approximation can capture the intended peripheral behavior: 𝑣 𝐶 is forced into 𝜑∗ (𝑋) since it shares the same coarse profile as 𝑣 𝐵 . Similarly, for the subset of superedges 𝐷 := {𝑒 1 } ⊆ 𝐸, representing “clearly observed evening coordination,” we obtain 𝜓∗ (𝐷) = ∅, 𝜓 ∗ (𝐷) = {𝑒 1 , 𝑒 2 }, because the only equivalence class {𝑒 1 , 𝑒 2 } is not contained in 𝐷 but intersects 𝐷 nontrivially. The sextuple 𝑉, 𝐸, 𝜑∗ , 𝜑∗ , 𝜓∗ , 𝜓 ∗ therefore forms a rough 2-SuperHyperGraph modeling uncertain knowledge about which delivery patterns and coordination links are central versus peripheral in the city–logistics network. 5.9 Fuzzy Directed 𝑛-Superhypergraph A fuzzy directed graph orients edges and assigns each vertex and arc a membership degree expressing directional connection uncertainty levels [914–916]. A fuzzy directed hypergraph generalizes directed graphs, using hyperarcs between vertex sets with fuzzy membership degrees modelling uncertain multiway influence [311, 917, 918]. We define the Fuzzy Directed 𝑛-Superhypergraph as an extension of the classical Fuzzy Directed Hypergraph (cf. [311, 917, 918]) by incorporating the hierarchical structure of 𝑛-Superhypergraphs (cf. [12]). Definition 5.9.1 (Fuzzy Directed Hypergraph). (cf. [311, 917, 919, 920]) Let 𝑉 be a nonempty set of vertices. A fuzzy directed hypergraph is a quadruple 𝐻 = 𝑉, 𝐸, 𝜎, 𝜇 , where • 𝐸 is a finite set of directed hyperarcs. Each 𝑒 ∈ 𝐸 is an ordered pair 𝑇 (𝑒), 𝐻 (𝑒) with 𝑇 (𝑒) ⊆ 𝑉, 𝑇 (𝑒) ≠ ∅, called its tail and head, respectively. 189 𝐻 (𝑒) ⊆ 𝑉 \ 𝑇 (𝑒)

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Chapter 5. Uncertain SuperHyperGraph • 𝜎 : 𝑉 → [0, 1] assigns to each vertex 𝑣 ∈ 𝑉 a membership degree 𝜎(𝑣). • 𝜇 : 𝐸 → [0, 1] assigns to each hyperarc 𝑒 ∈ 𝐸 a membership degree 𝜇(𝑒). These functions satisfy the consistency constraint 𝜇(𝑒) ≤ min 𝜎(𝑥), ∀ 𝑒 ∈ 𝐸. 𝑥 ∈𝑇 (𝑒) ∪ 𝐻 (𝑒) Definition 5.9.2 (Fuzzy Directed 𝑛-Superhypergraph). Let 𝑆 be a nonempty base set and let 𝑛 ≥ 0 be an integer. Define iterated powersets by P 0 (𝑆) = 𝑆, P 𝑘+1 (𝑆) = P P 𝑘 (𝑆) (𝑘 ≥ 0). A directed 𝑛-Superhypergraph is a pair DSHG (𝑛) = (𝑉, 𝐸) with 𝑉 ⊆ P 𝑛 (𝑆), 𝐸 ⊆ P 𝑛 (𝑆) × P 𝑛 (𝑆), where each 𝑒 ∈ 𝐸 is of the form Tail(𝑒), Head(𝑒) . A fuzzy directed 𝑛-Superhypergraph is then the quadruple 𝑉, 𝐸, 𝜎, 𝜇 , where • 𝜎 : 𝑉 → [0, 1] assigns to each 𝑛-supervertex 𝑣 a membership degree 𝜎(𝑣). • 𝜇 : 𝐸 → [0, 1] assigns to each directed 𝑛-superedge 𝑒 a membership degree 𝜇(𝑒). These satisfy the edge-appurtenance constraint 𝜇(𝑒) ≤ min 𝜎(𝑥), 𝑥 ∈Tail(𝑒) ∪ Head(𝑒) ∀ 𝑒 ∈ 𝐸. Example 5.9.3 (Fuzzy directed 1-SuperHyperGraph: emergency alert routing). Consider a small city with three emergency sensor stations 𝑆 := {𝑠1 , 𝑠2 , 𝑠3 }, for example “downtown” (𝑠1 ), “riverside” (𝑠2 ), and “industrial area” (𝑠3 ). We take 𝑛 = 1, so P 1 (𝑆) = P (𝑆), and define the set of 1-supervertices by 𝑣 1 := {𝑠1 , 𝑠2 }, 𝑣 2 := {𝑠2 , 𝑠3 }, 𝑣 3 := {𝑠1 , 𝑠3 }, representing overlapping monitoring zones. Then 𝑉 := {𝑣 1 , 𝑣 2 , 𝑣 3 } ⊆ P 1 (𝑆). We define two directed 1-superedges: 𝑒 1 := {𝑣 1 }, {𝑣 2 , 𝑣 3 } , 𝑒 2 := {𝑣 2 }, {𝑣 3 } , where 𝑒 1 models a possible alert propagation from the “downtown” zone 𝑣 1 to the other zones 𝑣 2 and 𝑣 3 , and 𝑒 2 models an alert from 𝑣 2 to 𝑣 3 . Put 𝐸 := {𝑒 1 , 𝑒 2 } ⊆ P 1 (𝑆) × P 1 (𝑆). Next, we assign fuzzy membership degrees to supervertices and superedges. Let 𝜎 : 𝑉 → [0, 1], 𝜎(𝑣 1 ) = 0.9, 𝜎(𝑣 2 ) = 0.7, 𝜎(𝑣 3 ) = 0.8, 190

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Chapter 5. Uncertain SuperHyperGraph where 𝜎(𝑣 𝑖 ) expresses the reliability/health of the monitoring zone 𝑣 𝑖 (e.g., sensor uptime and communication quality). For the directed superedges, define 𝜇 : 𝐸 → [0, 1], 𝜇(𝑒 1 ) = 0.7, 𝜇(𝑒 2 ) = 0.6. We check the edge–appurtenance constraint 𝜇(𝑒) ≤ min 𝜎(𝑥) 𝑥 ∈Tail(𝑒)∪Head(𝑒) for all 𝑒 ∈ 𝐸 . Indeed, Tail(𝑒 1 ) ∪ Head(𝑒 1 ) = {𝑣 1 , 𝑣 2 , 𝑣 3 }, min 𝜎 = min{0.9, 0.7, 0.8} = 0.7 ≥ 𝜇(𝑒 1 ), and Tail(𝑒 2 ) ∪ Head(𝑒 2 ) = {𝑣 2 , 𝑣 3 }, min 𝜎 = min{0.7, 0.8} = 0.7 ≥ 𝜇(𝑒 2 ). Thus (𝑉, 𝐸, 𝜎, 𝜇) is a fuzzy directed 1-Superhypergraph in the sense of Definition 5.9.2. Intuitively, the supervertices model overlapping sensor zones in the city, while the directed superedges model possible multi-zone alert propagation patterns. The vertex degrees 𝜎 quantify how reliable each zone is, and the edge degrees 𝜇 quantify the confidence that an emergency alert successfully flows along each multi-zone route. 5.10 Single-valued Neutrosophic Directed 𝑛-Superhypergraph A single-valued neutrosophic directed graph orients edges and assigns each vertex and arc triple degrees of truth, indeterminacy, falsity levels [807, 921]. A single-valued neutrosophic directed hypergraph uses oriented hyperarcs between vertex sets with neutrosophic truth, indeterminacy, falsity degrees modeling uncertainty precisely [807]. We define the Single-valued Neutrosophic Directed 𝑛-Superhypergraph as an extension of the classical Single-valued Neutrosophic Directed Hypergraph by incorporating the hierarchical structure of 𝑛-Superhypergraphs [314]. Definition 5.10.1 (Single-valued Neutrosophic Directed Hypergraph). (cf. [921]) A single-valued neutrosophic directed hypergraph on a nonempty set 𝑋 is an ordered pair 𝐺 ′ = 𝐺, {𝐹 𝑗 } 𝑛𝑗=1 , where 𝐺 = { 𝐺 𝑗 } 𝑛𝑗=1 , 𝐺 𝑗 = 𝑇 (𝐺 𝑗 ), 𝐻 (𝐺 𝑗 ) is a family of nontrivial single-valued neutrosophic subsets of 𝑋, with 𝑇 (𝐺 𝑗 ) = { 𝑣, 𝛼𝐺 (𝑣), 𝛽𝐺 (𝑣), 𝛾𝐺 (𝑣) | 𝑣 ∈ 𝑋 }, 𝐻 (𝐺 𝑗 ) = { 𝑣 ′ , 𝛼𝐺 (𝑣 ′ ), 𝛽𝐺 (𝑣 ′ ), 𝛾𝐺 (𝑣 ′ ) | 𝑣 ′ ∈ 𝑋 }, and each neutrosophic hyperarc is 𝐹 𝑗 𝑇 (𝐺 𝑗 ), 𝐻 (𝐺 𝑗 ) = (𝛼𝐹 𝑗 , 𝛽𝐹 𝑗 , 𝛾𝐹 𝑗 ) satisfying, for all 𝑗, 𝛼𝐹 𝑗 ≤ Û 𝛼𝐺 (𝑣) ∧ 𝛼𝐺 (𝑣 ′ ) , 𝑣 ∈𝑇 (𝐺 𝑗 ), 𝑣 ′ ∈ 𝐻 (𝐺 𝑗 ) 𝛽𝐹 𝑗 ≤ Û 𝛽𝐺 (𝑣) ∧ 𝛽𝐺 (𝑣 ′ ) , 𝑣 ∈𝑇 (𝐺 𝑗 ), 𝑣 ′ ∈ 𝐻 (𝐺 𝑗 ) 𝛾𝐹 𝑗 ≤ Ü 𝛾𝐺 (𝑣) ∧ 𝛾𝐺 (𝑣 ′ ) , 𝑣 ∈𝑇 (𝐺 𝑗 ), 𝑣 ′ ∈ 𝐻 (𝐺 𝑗 ) and 𝑋 = 𝑛 Ø supp(𝐺 𝑗 ). 𝑗=1 191

193.

Chapter 5. Uncertain SuperHyperGraph Definition 5.10.2 (Neutrosophic Directed Superhypergraph). Let 𝑆 be a nonempty base set and 𝑛 ≥ 0 an integer. Define P 0 (𝑆) = 𝑆, P 𝑘+1 (𝑆) = P (P 𝑘 (𝑆)) (𝑘 ≥ 0). A directed 𝑛-Superhypergraph is a pair DSHG (𝑛) = (𝑉, 𝐸) with 𝑉 ⊆ P 𝑛 (𝑆), 𝐸 ⊆ P 𝑛 (𝑆) × P 𝑛 (𝑆), where each 𝑒 ∈ 𝐸 is Tail(𝑒), Head(𝑒) . A single-valued neutrosophic directed 𝑛-Superhypergraph is the septuple 𝑉, 𝐸, 𝑇𝑉 , 𝐼𝑉 , 𝐹𝑉 , 𝑇𝐸 , 𝐼 𝐸 , 𝐹𝐸 , where 𝑇𝑉 , 𝐼𝑉 , 𝐹𝑉 : 𝑉 → [0, 1], 𝑇𝑉 (𝑣) + 𝐼𝑉 (𝑣) + 𝐹𝑉 (𝑣) ≤ 3, ∀𝑣 ∈ 𝑉, 𝑇𝐸 , 𝐼 𝐸 , 𝐹𝐸 : 𝐸 → [0, 1], 𝑇𝐸 (𝑒) ≤ min 𝑇𝑉 (𝑥), min 𝐼𝑉 (𝑥), min 𝐹𝑉 (𝑥), 𝑥 ∈Tail(𝑒)∪Head(𝑒) 𝐼 𝐸 (𝑒) ≤ 𝑥 ∈Tail(𝑒)∪Head(𝑒) 𝐹𝐸 (𝑒) ≤ ∀𝑒 ∈ 𝐸. 𝑥 ∈Tail(𝑒)∪Head(𝑒) Example 5.10.3 (Single-valued neutrosophic directed 1-Superhypergraph: parcel delivery network). Let the base set of local depots be 𝑆 := {𝑑1 , 𝑑2 , 𝑑3 }, where 𝑑1 is an “airport hub”, 𝑑2 a “city depot”, and 𝑑3 a “suburban depot”. Take 𝑛 = 1, so that P 1 (𝑆) = P (𝑆). Define three 1-supervertices (each representing a delivery zone covered jointly by several depots): 𝑣 1 := {𝑑1 , 𝑑2 }, 𝑣 2 := {𝑑2 , 𝑑3 }, 𝑣 3 := {𝑑1 , 𝑑3 }, and set 𝑉 := {𝑣 1 , 𝑣 2 , 𝑣 3 } ⊆ P 1 (𝑆). We introduce two directed 1-superedges: 𝑒 1 := {𝑣 1 }, {𝑣 2 } , 𝑒 2 := {𝑣 1 }, {𝑣 3 } , so that 𝑒 1 models a planned flow of parcels from the zone {𝑑1 , 𝑑2 } toward {𝑑2 , 𝑑3 } (airport → city+suburb), and 𝑒 2 models a flow from {𝑑1 , 𝑑2 } toward {𝑑1 , 𝑑3 } (airport+city → airport+suburb). Put 𝐸 := {𝑒 1 , 𝑒 2 } ⊆ P 1 (𝑆) × P 1 (𝑆). We now assign single-valued neutrosophic degrees to supervertices and superedges. For vertices, let 𝑇𝑉 , 𝐼𝑉 , 𝐹𝑉 : 𝑉 → [0, 1] be given by (𝑇𝑉 (𝑣 1 ), 𝐼𝑉 (𝑣 1 ), 𝐹𝑉 (𝑣 1 )) := (0.9, 0.1, 0.0), (𝑇𝑉 (𝑣 2 ), 𝐼𝑉 (𝑣 2 ), 𝐹𝑉 (𝑣 2 )) := (0.8, 0.15, 0.05), (𝑇𝑉 (𝑣 3 ), 𝐼𝑉 (𝑣 3 ), 𝐹𝑉 (𝑣 3 )) := (0.7, 0.2, 0.1). Here 𝑇𝑉 (𝑣) measures how strongly the zone 𝑣 is considered operationally reliable, 𝐼𝑉 (𝑣) measures indeterminacy (e.g. unknown traffic or staffing conditions), and 𝐹𝑉 (𝑣) measures the degree to which the zone is considered unreliable or unavailable. In each case 𝑇𝑉 (𝑣) + 𝐼𝑉 (𝑣) + 𝐹𝑉 (𝑣) ≤ 3 is trivially satisfied since each term lies in [0, 1]. 192

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Chapter 5. Uncertain SuperHyperGraph
For edges, define
𝑇𝐸 , 𝐼 𝐸 , 𝐹𝐸 : 𝐸 → [0, 1]
by
(𝑇𝐸 (𝑒 1 ), 𝐼 𝐸 (𝑒 1 ), 𝐹𝐸 (𝑒 1 )) := (0.75, 0.08, 0.00),
(𝑇𝐸 (𝑒 2 ), 𝐼 𝐸 (𝑒 2 ), 𝐹𝐸 (𝑒 2 )) := (0.70, 0.10, 0.05).
We verify the constraints from Definition 5.10.2. For 𝑒 1 we have
Tail(𝑒 1 ) ∪ Head(𝑒 1 ) = {𝑣 1 , 𝑣 2 },
so
min

𝑇𝑉 (𝑥) = min{0.9, 0.8} = 0.8 ≥ 𝑇𝐸 (𝑒 1 ),

min

𝐼𝑉 (𝑥) = min{0.1, 0.15} = 0.1 ≥ 𝐼 𝐸 (𝑒 1 ),

min

𝐹𝑉 (𝑥) = min{0.0, 0.05} = 0.0 ≥ 𝐹𝐸 (𝑒 1 ).

𝑥 ∈Tail(𝑒1 )∪Head(𝑒1 )
𝑥 ∈Tail(𝑒1 )∪Head(𝑒1 )
𝑥 ∈Tail(𝑒1 )∪Head(𝑒1 )

Similarly, for 𝑒 2 we have
Tail(𝑒 2 ) ∪ Head(𝑒 2 ) = {𝑣 1 , 𝑣 3 },
so
min 𝑇𝑉 = min{0.9, 0.7} = 0.7 ≥ 𝑇𝐸 (𝑒 2 ),

min 𝐼𝑉 = min{0.1, 0.2} = 0.1 ≥ 𝐼 𝐸 (𝑒 2 ),

min 𝐹𝑉 = min{0.0, 0.1} = 0.0 ≥ 𝐹𝐸 (𝑒 2 ).
Thus all neutrosophic edge-constraints are satisfied, and
𝑉, 𝐸, 𝑇𝑉 , 𝐼𝑉 , 𝐹𝑉 , 𝑇𝐸 , 𝐼 𝐸 , 𝐹𝐸



is a single-valued neutrosophic directed 1-Superhypergraph in the sense of Definition 5.10.2.
Operationally, this structure models a parcel delivery network where each 1-supervertex is an overlapping
group of depots, each directed 1-superedge represents a multi-depot shipping route, and the neutrosophic triples
quantify, for both zones and routes, the degrees of reliable operation (truth), uncertainty (indeterminacy), and
anticipated failure or disruption (falsity).

5.11

Fuzzy Tolerance SuperHyperGraph

A Fuzzy Tolerance Graph assigns fuzzy intervals and tolerances to vertices; edge degrees measure normalized
overlap, expressing uncertain pairwise compatibility [833, 922–924]. A Fuzzy Tolerance HyperGraph assigns
fuzzy intervals and tolerances to vertices; hyperedge degrees measure multiway normalized overlap, expressing
uncertain group feasibility [925]. A Fuzzy Tolerance SuperHyperGraph lifts fuzzy tolerance hypergraphs
to n-supervertices; superhyperedge degrees measure multiway overlap between hierarchical groups under
uncertainty [925].
Definition 5.11.1 (Fuzzy Tolerance Graph). [833, 922–924] Let 𝑉 be a finite nonempty set. For each 𝑣 ∈ 𝑉,
let 𝐼 𝑣 be a fuzzy interval on R (with core 𝑐(𝐼 𝑣 ) and support 𝑠(𝐼 𝑣 ), both compact real intervals), and let 𝑇𝑣 be a
fuzzy tolerance (a fuzzy number) whose core and support have positive lengths. Write ℓ(𝐽) for the (Lebesgue)
length of a real interval 𝐽 (and ℓ(∅) = 0).
Define the normalization

(
𝜌(𝑥, 𝑎) :=

min{1, 𝑥/𝑎},
0,

𝑎 > 0,
𝑎 = 0.

Define vertex-membership by
𝜎(𝑣) := ℎ(𝐼 𝑣 ) ∈ [0, 1]

(typically ℎ(𝐼 𝑣 ) = 1 for normal fuzzy intervals).

For distinct 𝑢, 𝑣 ∈ 𝑉, define edge-membership
n

o
𝜇(𝑢, 𝑣) := max 𝜌 ℓ(𝑐(𝐼𝑢 )∩𝑐(𝐼 𝑣 )), min{ℓ(𝑐(𝑇𝑢 )), ℓ(𝑐(𝑇𝑣 ))} , 𝜌 ℓ(𝑠(𝐼𝑢 )∩𝑠(𝐼 𝑣 )), min{ℓ(𝑠(𝑇𝑢 )), ℓ(𝑠(𝑇𝑣 ))} ∈ [0, 1],
and set 𝜇(𝑣, 𝑣) := 𝜎(𝑣). Then Ξ = (𝑉, 𝜎, 𝜇) is called a fuzzy tolerance graph.
193

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Chapter 5. Uncertain SuperHyperGraph
Example 5.11.2 (Fuzzy tolerance graph: uncertain call coordination). Let 𝑉 = {𝑋, 𝑌 , 𝑍 } be three consultants.
Their fuzzy availability intervals and fuzzy tolerances are summarized only by core/support intervals and
core/support lengths (hours):
𝑐(𝐼 𝑋 ) = [9, 12], 𝑠(𝐼 𝑋 ) = [8.5, 12.5],
𝑐(𝐼𝑌 ) = [10, 13], 𝑠(𝐼𝑌 ) = [9.5, 13.5],
𝑐(𝐼 𝑍 ) = [12, 14], 𝑠(𝐼 𝑍 ) = [10.5, 14.5],

ℓ(𝑐(𝑇𝑋 )) = 1.5, ℓ(𝑠(𝑇𝑋 )) = 3.0;
ℓ(𝑐(𝑇𝑌 )) = 1.0, ℓ(𝑠(𝑇𝑌 )) = 2.0;
ℓ(𝑐(𝑇𝑍 )) = 1.25, ℓ(𝑠(𝑇𝑍 )) = 2.5.

Take 𝜎(𝑋) = 𝜎(𝑌 ) = 𝜎(𝑍) = 1 (normal fuzzy intervals).
Compute 𝜇(𝑋, 𝑌 ):
ℓ(𝑐(𝐼 𝑋 ) ∩ 𝑐(𝐼𝑌 )) = ℓ( [10, 12]) = 2,

min{ℓ(𝑐(𝑇𝑋 )), ℓ(𝑐(𝑇𝑌 ))} = min{1.5, 1.0} = 1.0,

𝜌(2, 1.0) = min{1, 2/1} = 1.
Also
ℓ(𝑠(𝐼 𝑋 ) ∩ 𝑠(𝐼𝑌 )) = ℓ( [9.5, 12.5]) = 3,

min{ℓ(𝑠(𝑇𝑋 )), ℓ(𝑠(𝑇𝑌 ))} = min{3.0, 2.0} = 2.0,

𝜌(3, 2.0) = min{1, 3/2} = 1.
Hence 𝜇(𝑋, 𝑌 ) = max{1, 1} = 1.
Compute 𝜇(𝑋, 𝑍):
ℓ(𝑐(𝐼 𝑋 ) ∩ 𝑐(𝐼 𝑍 )) = ℓ( [9, 12] ∩ [12, 14]) = ℓ({12}) = 0,

min{1.5, 1.25} = 1.25,

ℓ(𝑠(𝐼 𝑋 )∩𝑠(𝐼 𝑍 )) = ℓ( [8.5, 12.5]∩[10.5, 14.5]) = ℓ( [10.5, 12.5]) = 2,

𝜌(0, 1.25) = 0,

min{3.0, 2.5} = 2.5,

𝜌(2, 2.5) = min{1, 2/2.5} = 0.8.

Hence 𝜇(𝑋, 𝑍) = max{0, 0.8} = 0.8.
Compute 𝜇(𝑌 , 𝑍):
ℓ(𝑐(𝐼𝑌 ) ∩ 𝑐(𝐼 𝑍 )) = ℓ( [10, 13] ∩ [12, 14]) = ℓ( [12, 13]) = 1,

min{1.0, 1.25} = 1.0,

ℓ(𝑠(𝐼𝑌 )∩𝑠(𝐼 𝑍 )) = ℓ( [9.5, 13.5]∩[10.5, 14.5]) = ℓ( [10.5, 13.5]) = 3,

𝜌(1, 1.0) = 1,

min{2.0, 2.5} = 2.0,

𝜌(3, 2.0) = 1.

Hence 𝜇(𝑌 , 𝑍) = 1. Therefore the fuzzy tolerance graph has full-feasibility edges 𝑋𝑌 , 𝑌 𝑍 and partial-feasibility
edge 𝑋 𝑍 with degree 0.8.
Definition 5.11.3 (Fuzzy Tolerance Hypergraph). [925] Let 𝑉 be a finite nonempty vertex set. For each 𝑣 ∈ 𝑉,
fix a fuzzy interval 𝐼 𝑣 and a fuzzy tolerance 𝑇𝑣 as above. For any nonempty 𝑒 ⊆ 𝑉, define
Ù

Ù

𝐿 𝑐 (𝑒) := ℓ
𝑐(𝐼 𝑣 ) ,
𝐿 𝑠 (𝑒) := ℓ
𝑠(𝐼 𝑣 ) ,
𝑣 ∈𝑒

𝑣 ∈𝑒

𝜏𝑐 (𝑒) := min ℓ(𝑐(𝑇𝑣 )),

𝜏𝑠 (𝑒) := min ℓ(𝑠(𝑇𝑣 )).

𝑣 ∈𝑒

𝑣 ∈𝑒

Let 𝜌 be as in the previous definition, and define the overlap score
𝜑(𝑒) := max{𝜌(𝐿 𝑐 (𝑒), 𝜏𝑐 (𝑒)), 𝜌(𝐿 𝑠 (𝑒), 𝜏𝑠 (𝑒))} ∈ [0, 1].
Define the (crisp) edge universe
𝐸 := { 𝑒 ⊆ 𝑉 : |𝑒| ≥ 2, 𝜑(𝑒) > 0 }.
Define fuzzy memberships
n
o
𝜇(𝑒) := min 𝜑(𝑒), min 𝜎(𝑣) ∈ [0, 1],

𝜎(𝑣) := min{ℎ(𝐼 𝑣 ), ℎ(𝑇𝑣 )} ∈ [0, 1],

𝑣 ∈𝑒

and the incidence membership
(
𝜂(𝑣, 𝑒) :=

𝜇(𝑒),
0,

𝑣 ∈ 𝑒,
𝑣 ∉ 𝑒.

Then 𝐻 = (𝑉, 𝐸; 𝜎, 𝜇, 𝜂) is called a fuzzy tolerance hypergraph.
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Chapter 5. Uncertain SuperHyperGraph
Example 5.11.4 (Fuzzy tolerance hypergraph: joint specialist consultation). Let 𝑉 = {𝐶, 𝑁, 𝑂} denote
Cardiology, Neurology, Orthopedics. Use (hours)
𝑐(𝐼𝐶 ) = [9, 12], 𝑠(𝐼𝐶 ) = [8.5, 12.5], ℓ(𝑐(𝑇𝐶 )) = 1.0, ℓ(𝑠(𝑇𝐶 )) = 1.5,
𝑐(𝐼 𝑁 ) = [10, 13], 𝑠(𝐼 𝑁 ) = [9.5, 13.5], ℓ(𝑐(𝑇𝑁 )) = 1.2, ℓ(𝑠(𝑇𝑁 )) = 2.0,
𝑐(𝐼𝑂 ) = [11, 14], 𝑠(𝐼𝑂 ) = [10.5, 14.5], ℓ(𝑐(𝑇𝑂 )) = 1.5, ℓ(𝑠(𝑇𝑂 )) = 2.5.
Assume heights (ℎ(𝐼𝐶 ), ℎ(𝑇𝐶 )) = (0.95, 0.90), (ℎ(𝐼 𝑁 ), ℎ(𝑇𝑁 )) = (0.90, 0.95), (ℎ(𝐼𝑂 ), ℎ(𝑇𝑂 )) = (0.85, 0.80),
hence
𝜎(𝐶) = min{0.95, 0.90} = 0.90,

𝜎(𝑁) = min{0.90, 0.95} = 0.90,

𝜎(𝑂) = min{0.85, 0.80} = 0.80.

Compute 𝜑({𝐶, 𝑁, 𝑂}):
𝐿 𝑐 ({𝐶, 𝑁, 𝑂}) = ℓ([9, 12] ∩ [10, 13] ∩ [11, 14]) = ℓ( [11, 12]) = 1,
𝜏𝑐 ({𝐶, 𝑁, 𝑂}) = min{1.0, 1.2, 1.5} = 1.0,

𝜌(𝐿 𝑐 , 𝜏𝑐 ) = 𝜌(1, 1) = 1.

Also
𝐿 𝑠 ({𝐶, 𝑁, 𝑂}) = ℓ([8.5, 12.5] ∩ [9.5, 13.5] ∩ [10.5, 14.5]) = ℓ( [10.5, 12.5]) = 2,
𝜏𝑠 ({𝐶, 𝑁, 𝑂}) = min{1.5, 2.0, 2.5} = 1.5,

𝜌(𝐿 𝑠 , 𝜏𝑠 ) = 𝜌(2, 1.5) = min{1, 2/1.5} = 1.

Hence 𝜑({𝐶, 𝑁, 𝑂}) = max{1, 1} = 1 and
𝜇({𝐶, 𝑁, 𝑂}) = min{1, min(𝜎(𝐶), 𝜎(𝑁), 𝜎(𝑂))} = min{1, 0.80} = 0.80.
Similarly, for the pairs:
𝜇({𝐶, 𝑁 }) = min{1, min(0.90, 0.90)} = 0.90,

𝜇({𝐶, 𝑂}) = min{1, min(0.90, 0.80)} = 0.80,

𝜇({𝑁, 𝑂}) = min{1, min(0.90

and 𝜂(𝑣, 𝑒) = 𝜇(𝑒) for 𝑣 ∈ 𝑒 (otherwise 0). This quantifies feasibility of multi-clinic sessions under uncertainty.
Definition 5.11.5 (Fuzzy Tolerance SuperHyperGraph). [925] Fix 𝑛 ∈ N0 and a finite base set 𝑉0 . Let
𝑉 ⊆ P 𝑛 (𝑉0 ) be a finite nonempty set of 𝑛-supervertices. For each 𝑣 ∈ 𝑉, choose a fuzzy interval 𝐼 𝑣 and a
fuzzy tolerance 𝑇𝑣 .
For any nonempty 𝑒 ⊆ 𝑉 define
Ù

Ù

𝐿 𝑐 (𝑒) := ℓ
𝑐(𝐼 𝑣 ) , 𝐿 𝑠 (𝑒) := ℓ
𝑠(𝐼 𝑣 ) ,
𝑣 ∈𝑒

𝜏𝑐 (𝑒) := min ℓ(𝑐(𝑇𝑣 )),
𝑣 ∈𝑒

𝑣 ∈𝑒

𝜑(𝑒) := max{𝜌(𝐿 𝑐 (𝑒), 𝜏𝑐 (𝑒)), 𝜌(𝐿 𝑠 (𝑒), 𝜏𝑠 (𝑒))} ∈ [0, 1],

𝜏𝑠 (𝑒) := min ℓ(𝑠(𝑇𝑣 )),
𝑣 ∈𝑒

𝜎(𝑣) := min{ℎ(𝐼 𝑣 ), ℎ(𝑇𝑣 )} ∈ [0, 1].

Let the (crisp) superedge universe be
𝐸 := { 𝑒 ⊆ 𝑉 : |𝑒| ≥ 2 }.
Define superedge-membership and incidence-membership by
n

o

𝜇(𝑒) := min 𝜑(𝑒), min 𝜎(𝑣) ,
𝑣 ∈𝑒

(
𝜂(𝑣, 𝑒) :=

𝜇(𝑒),
0,

𝑣 ∈ 𝑒,
𝑣 ∉ 𝑒.

(𝑛)
Then 𝑆 𝐹𝑇
= (𝑉, 𝐸; 𝜎, 𝜇, 𝜂) is called a fuzzy tolerance 𝑛-SuperHyperGraph.

Example 5.11.6 (Fuzzy tolerance superhypergraph: workshops among teams (level 𝑛 = 1)). Let 𝑉0 =
{𝑎, 𝑏, 𝑐, 𝑑, 𝑒, 𝑓 } be employees and take 𝑛 = 1. Define three team supervertices
𝑇1 = {𝑎, 𝑏, 𝑐},

𝑇2 = {𝑐, 𝑑},

𝑇3 = {𝑑, 𝑒, 𝑓 },

𝑉 = {𝑇1 , 𝑇2 , 𝑇3 } ⊆ P (𝑉0 ).

Assign fuzzy availability intervals and fuzzy tolerances via cores/supports (hours):
𝑐(𝐼𝑇1 ) = [9, 12], 𝑠(𝐼𝑇1 ) = [8.5, 12.5], ℓ(𝑐(𝑇𝑇1 )) = 1.5, ℓ(𝑠(𝑇𝑇1 )) = 2.5,
195

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Chapter 5. Uncertain SuperHyperGraph 𝑐(𝐼𝑇2 ) = [10, 14], 𝑠(𝐼𝑇2 ) = [9.5, 14.5], ℓ(𝑐(𝑇𝑇2 )) = 1.0, ℓ(𝑠(𝑇𝑇2 )) = 2.0, 𝑐(𝐼𝑇3 ) = [11, 13], 𝑠(𝐼𝑇3 ) = [10.5, 13.5], ℓ(𝑐(𝑇𝑇3 )) = 1.0, ℓ(𝑠(𝑇𝑇3 )) = 1.5. Heights: (ℎ(𝐼𝑇1 ), ℎ(𝑇𝑇1 )) = (0.95, 0.90), (ℎ(𝐼𝑇2 ), ℎ(𝑇𝑇2 )) = (0.90, 0.90), (ℎ(𝐼𝑇3 ), ℎ(𝑇𝑇3 )) = (0.90, 0.85), so 𝜎(𝑇1 ) = min{0.95, 0.90} = 0.90, 𝜎(𝑇2 ) = min{0.90, 0.90} = 0.90, 𝜎(𝑇3 ) = min{0.90, 0.85} = 0.85. Check the triple overlap score 𝜑({𝑇1 , 𝑇2 , 𝑇3 }): 𝐿 𝑐 = ℓ( [9, 12]∩[10, 14]∩[11, 13]) = ℓ( [11, 12]) = 1, 𝜏𝑐 = min{1.5, 1.0, 1.0} = 1.0, 𝐿 𝑠 = ℓ( [8.5, 12.5]∩[9.5, 14.5]∩[10.5, 13.5]) = ℓ( [10.5, 12.5]) = 2, 𝜌(𝐿 𝑐 , 𝜏𝑐 ) = 𝜌(1, 1) = 1, 𝜏𝑠 = min{2.5, 2.0, 1.5} = 1.5, 𝜌(𝐿 𝑠 , 𝜏𝑠 ) = 𝜌(2, 1.5) = 1. Hence 𝜑({𝑇1 , 𝑇2 , 𝑇3 }) = 1 and thus 𝜇({𝑇1 , 𝑇2 , 𝑇3 }) = min{1, min(𝜎(𝑇1 ), 𝜎(𝑇2 ), 𝜎(𝑇3 ))} = min{1, 0.85} = 0.85. For the pairs, the same overlap computation gives 𝜑({𝑇𝑖 , 𝑇 𝑗 }) = 1, so 𝜇({𝑇1 , 𝑇2 }) = min{1, min(0.90, 0.90)} = 0.90, 𝜇({𝑇1 , 𝑇3 }) = min{1, min(0.90, 0.85)} = 0.85, 𝜇({𝑇2 , 𝑇3 }) = min{1, min(0.90, Finally, 𝜂(𝑇𝑖 , 𝑒) = 𝜇(𝑒) if 𝑇𝑖 ∈ 𝑒 (else 0). This yields a fuzzy tolerance superhypergraph quantifying feasibility of joint workshops among teams under uncertainty. 5.12 Neutrosophic HyperEdgeWeighted 𝑛-SuperHyperGraph A Neutrosophic HyperEdgeWeighted 𝑛-SuperHyperGraph assigns each 𝑛-superedge a neutrosophic weight (𝑇, 𝐼, 𝐹), capturing uncertain edge strength at level 𝑛 [926, 927]. Definition 5.12.1 (Single-valued neutrosophic weight domain). [927] Define the (single-valued) neutrosophic weight domain by n o N𝑆𝑉 := (𝑇, 𝐼, 𝐹) ∈ [0, 1] 3 0 ≤ 𝑇 + 𝐼 + 𝐹 ≤ 3 . Definition 5.12.2 (Neutrosophic HyperEdgeWeighted 𝑛-SuperHyperGraph). [927] Let H (𝑛) = (𝑉, 𝐸) be an 𝑛SuperHyperGraph over 𝑉0 . A Neutrosophic HyperEdgeWeighted 𝑛-SuperHyperGraph (briefly, NHEW-𝑛-SHG) is a triple Ω = (𝑉, 𝐸, 𝑊) where 𝑊 is a neutrosophic hyperedge-weight function 𝑊 : 𝐸 −→ N𝑆𝑉 , 𝑒 ↦−→ 𝑊 (𝑒) = (𝑇𝑒 , 𝐼𝑒 , 𝐹𝑒 ). Here 𝑇𝑒 is the truth-component, 𝐼𝑒 the indeterminacy-component, and 𝐹𝑒 the falsity-component of the superhyperedge 𝑒. Example 5.12.3 (A concrete Neutrosophic HyperEdgeWeighted 1-SuperHyperGraph). Let the finite base vertex set be 𝑉0 = {𝑎, 𝑏, 𝑐}, 𝑛 = 1, P1 (𝑉0 ) = P (𝑉0 ). Define the 1-supervertex set (each element is a nonempty subset of 𝑉0 ) by 𝑉 = 𝑣 1 , 𝑣 2 , 𝑣 3 , 𝑣 4 := {𝑎, 𝑏}, {𝑏, 𝑐}, {𝑎}, {𝑐} ⊆ P (𝑉0 ) \ {∅}. Define two 1-superhyperedges (each is a nonempty set of supervertices) by 𝐸 = {𝑒 1 , 𝑒 2 }, 𝑒 1 = {𝑣 1 , 𝑣 2 , 𝑣 4 } = {𝑎, 𝑏}, {𝑏, 𝑐}, {𝑐} , 𝑒 2 = {𝑣 1 , 𝑣 3 } = {𝑎, 𝑏}, {𝑎} . Thus H (1) = (𝑉, 𝐸) is a 1-SuperHyperGraph. Now assign neutrosophic hyperedge-weights by a map 𝑊 : 𝐸 → [0, 1] 3 , 𝑊 (𝑒) = (𝑇𝑒 , 𝐼𝑒 , 𝐹𝑒 ), 196

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Chapter 5. Uncertain SuperHyperGraph for instance 𝑊 (𝑒 1 ) = (0.85, 0.10, 0.25), 𝑊 (𝑒 2 ) = (0.40, 0.55, 0.30). Constraint check: 0 ≤ 0.85 + 0.10 + 0.25 = 1.20 ≤ 3, 0 ≤ 0.40 + 0.55 + 0.30 = 1.25 ≤ 3. Hence Ω = (𝑉, 𝐸, 𝑊) is a concrete Neutrosophic HyperEdgeWeighted 1-SuperHyperGraph. Theorem 5.12.4 (Neutrosophic HyperEdgeWeighted 𝑛-SuperHyperGraphs generalize 𝑛-SuperHyperGraphs). Let 𝑛 ≥ 0. For every (finite) 𝑛-SuperHyperGraph H (𝑛) = (𝑉 (𝑛) , 𝐸 (𝑛) ), there exists a Neutrosophic HyperEdgeWeighted 𝑛-SuperHyperGraph Ω (𝑛) = 𝑉 (𝑛) , 𝐸 (𝑛) , 𝑊 whose underlying 𝑛-SuperHyperGraph is exactly H (𝑛) . Equivalently, the forgetful map 𝑈 : (𝑉 (𝑛) , 𝐸 (𝑛) , 𝑊) ↦−→ (𝑉 (𝑛) , 𝐸 (𝑛) ) from Neutrosophic HyperEdgeWeighted 𝑛-SuperHyperGraphs to 𝑛-SuperHyperGraphs is surjective on objects. Proof. Fix an arbitrary (finite) 𝑛-SuperHyperGraph H (𝑛) = (𝑉 (𝑛) , 𝐸 (𝑛) ). Define a hyperedge-weight map 𝑊 : 𝐸 (𝑛) → [0, 1] 3 by choosing the constant neutrosophic triple for every 𝑒 ∈ 𝐸 (𝑛) . 𝑊 (𝑒) := (1, 0, 0) This is well-defined because (1, 0, 0) ∈ [0, 1] 3 , and it satisfies the usual basic feasibility constraint used for neutrosophic weights: 0 ≤ 1 + 0 + 0 = 1 ≤ 3. Now set Ω (𝑛) := 𝑉 (𝑛) , 𝐸 (𝑛) , 𝑊 . By construction, Ω (𝑛) has the same 𝑛-supervertex set and the same 𝑛-superedge family as H (𝑛) , and 𝑊 assigns a valid neutrosophic weight to each 𝑛-superedge. Hence Ω (𝑛) is a Neutrosophic HyperEdgeWeighted 𝑛-SuperHyperGraph. Finally, forgetting the weights yields 𝑈 Ω (𝑛) = (𝑉 (𝑛) , 𝐸 (𝑛) ) = H (𝑛) . Therefore every 𝑛-SuperHyperGraph arises as the underlying structure of some Neutrosophic HyperEdgeWeighted 𝑛-SuperHyperGraph, proving the claim. □ Note that, by following the construction of Neutrosophic HyperEdgeWeighted 𝑛-SuperHyperGraphs, one can define a Fuzzy HyperEdgeWeighted 𝑛-SuperHyperGraph in the following manner. Definition 5.12.5 (Fuzzy HyperEdgeWeighted 𝑛-SuperHyperGraph). Let 𝑉0 be a nonempty finite base set and let P0 (𝑉0 ) := 𝑉0 , P 𝑘+1 (𝑉0 ) := P (P 𝑘 (𝑉0 )) (𝑘 ≥ 0). Fix an integer 𝑛 ≥ 0. An 𝑛-SuperHyperGraph is a pair H (𝑛) = (𝑉 (𝑛) , 𝐸 (𝑛) ), 197

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Chapter 5. Uncertain SuperHyperGraph where 𝑉 (𝑛) ⊆ P𝑛 (𝑉0 ) is a finite set of 𝑛-supervertices and 𝐸 (𝑛) ⊆ P (𝑉 (𝑛) ) \ {∅} is a finite family of 𝑛-superedges. A Fuzzy HyperEdgeWeighted 𝑛-SuperHyperGraph is a triple H𝐹(𝑛) := 𝑉 (𝑛) , 𝐸 (𝑛) , 𝑤 𝐹 , where 𝑉 (𝑛) , 𝐸 (𝑛) is an 𝑛-SuperHyperGraph and 𝑤 𝐹 : 𝐸 (𝑛) −→ [0, 1] is a fuzzy hyperedge-weight function. For each 𝑒 ∈ 𝐸 (𝑛) , the value 𝑤 𝐹 (𝑒) is interpreted as the (fuzzy) strength/reliability/capacity of the 𝑛-superedge 𝑒. Theorem 5.12.6 (Neutrosophic HyperEdgeWeighted 𝑛-SuperHyperGraphs generalize fuzzy ones). Every Fuzzy HyperEdgeWeighted 𝑛-SuperHyperGraph is obtained as a special case of a Neutrosophic HyperEdgeWeighted 𝑛-SuperHyperGraph. More precisely, there is an embedding n o n o Φ : Fuzzy HyperEdgeWeighted 𝑛-SuperHyperGraphs ↩→ Neutrosophic HyperEdgeWeighted 𝑛-SuperHyperGraphs defined by keeping (𝑉 (𝑛) , 𝐸 (𝑛) ) and mapping fuzzy weights 𝑤 𝐹 to neutrosophic weights 𝑤 𝑁 via 𝑤 𝑁 (𝑒) := 𝑤 𝐹 (𝑒), 0, 1 − 𝑤 𝐹 (𝑒) (𝑒 ∈ 𝐸 (𝑛) ). Proof. Let H𝐹(𝑛) = (𝑉 (𝑛) , 𝐸 (𝑛) , 𝑤 𝐹 ) be any Fuzzy HyperEdgeWeighted 𝑛-SuperHyperGraph. Define a map 𝑤 𝑁 : 𝐸 (𝑛) → [0, 1] 3 by 𝑤 𝑁 (𝑒) := 𝑇 (𝑒), 𝐼 (𝑒), 𝐹 (𝑒) := 𝑤 𝐹 (𝑒), 0, 1 − 𝑤 𝐹 (𝑒) (𝑒 ∈ 𝐸 (𝑛) ). Since 𝑤 𝐹 (𝑒) ∈ [0, 1], we have 0 ≤ 𝑤 𝐹 (𝑒) ≤ 1, hence 0 ≤ 𝑇 (𝑒) = 𝑤 𝐹 (𝑒) ≤ 1, 𝐼 (𝑒) = 0 ∈ [0, 1], 0 ≤ 𝐹 (𝑒) = 1 − 𝑤 𝐹 (𝑒) ≤ 1, so indeed 𝑤 𝑁 (𝑒) ∈ [0, 1] 3 for every 𝑒 ∈ 𝐸 (𝑛) . Therefore H 𝑁(𝑛) := 𝑉 (𝑛) , 𝐸 (𝑛) , 𝑤 𝑁 is a Neutrosophic HyperEdgeWeighted 𝑛-SuperHyperGraph, and it has the same underlying 𝑛-SuperHyperGraph (𝑉 (𝑛) , 𝐸 (𝑛) ) as H𝐹(𝑛) . Moreover, the construction is injective on weights: if 𝑤 𝐹 and 𝑤 ′𝐹 satisfy 𝑤 𝐹 (𝑒), 0, 1 − 𝑤 𝐹 (𝑒) = 𝑤 ′𝐹 (𝑒), 0, 1 − 𝑤 ′𝐹 (𝑒) for all 𝑒, then comparing first coordinates gives 𝑤 𝐹 (𝑒) = 𝑤 ′𝐹 (𝑒) for all 𝑒, hence 𝑤 𝐹 = 𝑤 ′𝐹 . Thus the mapping Φ(H𝐹(𝑛) ) = H 𝑁(𝑛) is an embedding, showing that Neutrosophic HyperEdgeWeighted 𝑛-SuperHyperGraphs generalize Fuzzy HyperEdgeWeighted 𝑛-SuperHyperGraphs. □ 198

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[beta]

Chapter 6

Applications of SuperHyperGraph

This chapter presents several applications of SuperHyperGraphs. Classical Graphs and HyperGraphs are widely
used in many fields—such as chemistry, physics, engineering, and informatics—because of their conceptual
flexibility and modeling power. SuperHyperGraphs inherit and extend these advantages, and therefore offer
promising applications in chemistry, physics, engineering, and other domains where multi-level and multistructure relationships naturally arise.

6.1

Molecular SuperHyperGraphs

A molecular graph represents a molecule by treating atoms as vertices and covalent bonds as labeled edges
in a simple graph structure [30, 928, 929]. A molecular hypergraph extends this idea by allowing hyperedges
that connect several atoms at once, thereby capturing functional groups, aromatic rings, delocalized electron
systems, and other multi-atom chemical interactions [31, 298, 930, 931]. A molecular SuperHyperGraph
further organizes atoms, bonds, fragments, and whole molecular units across iterated powerset layers, offering
a hierarchical representation of complex chemical structures, multi-scale motifs, and overlapping functional
contexts [32, 932]. Related notions include Chemical Graphs [750, 933, 934], Chemical HyperGraphs [55, 56,
935], Chemical SuperHyperGraphs [57,58], Goal-directed molecular graph [936,937], and Chemical Reaction
Networks [938–940], which appear in computational chemistry, cheminformatics, and reaction-mechanism
modeling.
Definition 6.1.1 (Molecular Graph). (cf. [30]) A molecular graph is a labeled simple graph
𝐺 = (𝑉, 𝐸, ℓ𝑉 , ℓ𝐸 ),
where
• 𝑉 is a finite set of atoms;

• 𝐸 ⊆ {𝑢, 𝑣} | 𝑢, 𝑣 ∈ 𝑉, 𝑢 ≠ 𝑣 is the set of covalent bonds;
• ℓ𝑉 : 𝑉 → L𝑉 assigns to each vertex 𝑣 ∈ 𝑉 its atomic label (e.g. element symbol such as C, H, O);
• ℓ𝐸 : 𝐸 → L 𝐸 assigns to each edge 𝑒 ∈ 𝐸 its bond label (e.g. single, double, triple).
Thus vertices represent atoms, edges represent bonds, and the labeling functions encode atom types and bond
types.
Definition 6.1.2 (Molecular 𝑛-SuperHyperGraph). [32, 932] Let 𝑉0 be a finite set of bond identifiers of a
molecule. Define the iterated powersets by

P0 (𝑉0 ) := 𝑉0 ,
P 𝑘+1 (𝑉0 ) := P P 𝑘 (𝑉0 ) (𝑘 ≥ 0),
where P(·) denotes the usual powerset.
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Chapter 6. Applications of SuperHyperGraph
Fix an integer 𝑛 ≥ 0. A molecular 𝑛-SuperHyperGraph on the base set 𝑉0 is a quintuple

𝐻 (𝑛) = 𝑉𝐻 , 𝐸 𝐻 , 𝜕, ℓ𝑉𝐻 , ℓ𝐸𝐻 ,
where
• 𝑉𝐻 ⊆ P𝑛 (𝑉0 ) is a finite set of 𝑛-supervertices (each 𝑣 ∈ 𝑉𝐻 represents a possibly nested collection of
bonds up to level 𝑛);
• 𝐸 𝐻 is a finite set of 𝑛-superedges;
• 𝜕 : 𝐸 𝐻 → P∗ (𝑉𝐻 ) is the incidence map, with P∗ (𝑉𝐻 ) := P (𝑉𝐻 ) \ {∅}; for 𝑒 ∈ 𝐸 𝐻 , the set 𝜕 (𝑒) ⊆ 𝑉𝐻
is the family of 𝑛-supervertices incident with the 𝑛-superedge 𝑒;
• ℓ𝑉𝐻 : 𝑉𝐻 → L𝑉 assigns to each 𝑛-supervertex 𝑣 a vertex label (for example, a bond-pattern type,
functional-group name, or moiety type);
• ℓ𝐸𝐻 : 𝐸 𝐻 → L 𝐸 assigns to each 𝑛-superedge 𝑒 an edge label (for example, an atom symbol, a fragment
name, or a whole-molecule/functional-unit identifier).
The underlying 𝑛-SuperHyperGraph of 𝐻 (𝑛) is the triple (𝑉𝐻 , 𝐸 𝐻 , 𝜕). For 𝑛 = 0, the condition 𝑉𝐻 ⊆ P0 (𝑉0 ) =
𝑉0 implies that each vertex corresponds to a single bond identifier, and the structure reduces to a labeled
molecular hypergraph on 𝑉0 .
Example 6.1.3 (Molecular 1-SuperHyperGraph for a benzene core). Let 𝑉0 be the set of bond identifiers of a
benzene ring [941],
𝑉0 = {𝑏 1 , 𝑏 2 , 𝑏 3 , 𝑏 4 , 𝑏 5 , 𝑏 6 },
where each 𝑏 𝑖 denotes the C–C bond between 𝐶𝑖 and 𝐶𝑖+1 (with 𝐶7 := 𝐶1 ). Then
P0 (𝑉0 ) := 𝑉0 ,

P1 (𝑉0 ) := P (𝑉0 ).

Fix 𝑛 = 1. Define the set of 1-supervertices by
n
o
𝑉𝐻 := 𝑣 ring , 𝑣 ortho , 𝑣 meta , 𝑣 para ⊆ P1 (𝑉0 ),
where
𝑣 ring := {𝑏 1 , 𝑏 2 , 𝑏 3 , 𝑏 4 , 𝑏 5 , 𝑏 6 }

(entire aromatic ring),

𝑣 ortho := {𝑏 1 , 𝑏 2 }

(two adjacent bonds: an ortho-like fragment),

𝑣 meta := {𝑏 1 , 𝑏 3 }

(two bonds at meta separation),

𝑣 para := {𝑏 1 , 𝑏 4 }

(two bonds at para separation).

Let 𝐸 𝐻 := {𝑒 benzene } consist of a single 1-superedge, with incidence map
𝜕 (𝑒 benzene ) := {𝑣 ring , 𝑣 ortho , 𝑣 meta , 𝑣 para } ⊆ 𝑉𝐻 .
Interpret 𝑒 benzene as the “benzene core context” that simultaneously relates the whole aromatic ring and its
standard substitution patterns.
Choose label sets
L𝑉 := {“ring”, “ortho”, “meta”, “para”},

L 𝐸 := {“benzene core”},

and define
ℓ𝑉𝐻 (𝑣 ring ) = “ring”,

ℓ𝑉𝐻 (𝑣 ortho ) = “ortho”,

ℓ𝑉𝐻 (𝑣 meta ) = “meta”,

ℓ𝑉𝐻 (𝑣 para ) = “para”,

ℓ𝐸𝐻 (𝑒 benzene ) = “benzene core”.
Then
𝐻 (1) := 𝑉𝐻 , 𝐸 𝐻 , 𝜕, ℓ𝑉𝐻 , ℓ𝐸𝐻



is a molecular 1-SuperHyperGraph: each 1-supervertex is a bond-based fragment (subset of 𝑉0 ), and the single
1-superedge encodes the benzene core that ties these fragments together.
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Chapter 6. Applications of SuperHyperGraph Example 6.1.4 (Molecular 2-SuperHyperGraph for an aspirin-like molecule). Consider an aspirin-like aromatic molecule [942] with a ring, a carboxyl group, and an ester group. Let 𝑉0 be the set of selected bond identifiers 𝑉0 := {𝑏 ring,1 , 𝑏 ring,2 , 𝑏 ring,3 , 𝑏 COOH,1 , 𝑏 COOH,2 , 𝑏 ester,1 , 𝑏 ester,2 }, where, for example, 𝑏 ring,𝑖 are representative C–C bonds in the aromatic ring, 𝑏 COOH,1 , 𝑏 COOH,2 are bonds in the carboxyl group, and 𝑏 ester,1 , 𝑏 ester,2 are bonds in the ester group. Define P0 (𝑉0 ) := 𝑉0 , P1 (𝑉0 ) := P (𝑉0 ), P2 (𝑉0 ) := P P1 (𝑉0 ) . At level 1, consider the following bond-based fragments 𝑋ring := {𝑏 ring,1 , 𝑏 ring,2 , 𝑏 ring,3 } ∈ P1 (𝑉0 ), 𝑋COOH := {𝑏 COOH,1 , 𝑏 COOH,2 } ∈ P1 (𝑉0 ), 𝑋ester := {𝑏 ester,1 , 𝑏 ester,2 } ∈ P1 (𝑉0 ). Fix 𝑛 = 2. Define the 2-supervertex set 𝑉𝐻 ⊆ P2 (𝑉0 ) by 𝑣 local := {𝑋ring , 𝑋COOH } ∈ P2 (𝑉0 ) (aromatic ring + carboxyl fragment), 𝑣 global := {𝑋ring , 𝑋COOH , 𝑋ester } ∈ P2 (𝑉0 ) (ring + carboxyl + ester = full aspirin motif), 𝑉𝐻 := {𝑣 local , 𝑣 global }. Let 𝐸 𝐻 := {𝑒 local , 𝑒 aspirin }, with incidence map 𝜕 (𝑒 local ) := {𝑣 local }, 𝜕 (𝑒 aspirin ) := {𝑣 global }. Here 𝑒 local encodes a “salicylic-acid-like” local motif (ring plus carboxyl group), while 𝑒 aspirin encodes the full aspirin pharmacophore (ring, carboxyl, and ester). Choose label sets L 𝐸 := {“salicylic core”, “aspirin pharmacophore”}, L𝑉 := {“local fragment”, “aspirin motif”}, and define ℓ𝑉𝐻 (𝑣 local ) = “local fragment”, ℓ𝐸𝐻 (𝑒 local ) = “salicylic core”, ℓ𝑉𝐻 (𝑣 global ) = “aspirin motif”, ℓ𝐸𝐻 (𝑒 aspirin ) = “aspirin pharmacophore”. Then 𝐻 (2) := 𝑉𝐻 , 𝐸 𝐻 , 𝜕, ℓ𝑉𝐻 , ℓ𝐸𝐻 is a molecular 2-SuperHyperGraph. Each 2-supervertex is a set of level-1 bond fragments (elements of P1 (𝑉0 )), so elements of 𝑉𝐻 belong to P2 (𝑉0 ), and superedges distinguish different chemically meaningful groupings: a local aromatic–carboxyl core and the full aspirin-like pharmacophore. For reference, an overview of molecular graph, molecular hypergraph, and molecular 𝑛-SuperHyperGraph viewpoints is presented in Table 6.1. 201

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Chapter 6. Applications of SuperHyperGraph Table 6.1: Concise overview of molecular graph, molecular hypergraph, and molecular 𝑛-SuperHyperGraph viewpoints. Aspect Molecular Graph Molecular HyperGraph Carrier objects Atoms (vertices) Atoms (vertices) Relation objects Bonds (edges) Multi-atom interactions (hyperedges) What it captures Pairwise connectivity, bond types Functional groups, rings, multi-body constraints Typical labels/weights Atom type, bond order Use cases (keywords) QSAR, cheminformatics, descriptors Hyperedge type (group/ring), interaction strength Hypergraph neural nets, group-level chemistry 6.2 Molecular 𝑛SuperHyperGraph 𝑛-supervertices (nested fragments over a base carrier) Hierarchical relations among fragments (superhyperedges) Multi-scale motifs, overlapping fragments, context across levels Fragment type, role, reliability/importance across levels Multi-level representation, coarse-to-fine reasoning Competition SuperHyperGraphs Competition graphs connect two vertices when they share a common out-neighbor in a digraph, modeling competition for the same resource [943–945]. Related concepts such as fuzzy competition graphs [946–948] and neutrosophic competition graphs [878, 949] are also known. A competition hypergraph has vertices of a digraph and hyperedges grouping vertices sharing the same in-neighborhood prey target vertex node [950–952]. A competition Superhypergraph lifts this construction to n-supervertices, forming superhyperedges connecting supervertices whose flattened elements share predator relationships in digraphs [35]. Definition 6.2.1 (Competition hypergraph). [950–952] Let 𝐷 = (𝑉, 𝐴) be a finite directed graph, where 𝑉 is the vertex set and 𝐴 ⊆ 𝑉 × 𝑉 is the arc set. For each vertex 𝑣 ∈ 𝑉, its in–neighborhood is 𝑁 − (𝑣) := { 𝑢 ∈ 𝑉 | (𝑢, 𝑣) ∈ 𝐴 }. The competition hypergraph of 𝐷 is the hypergraph CH(𝐷) := (𝑉, 𝐸), where the hyperedge family 𝐸 is defined by 𝐸 := 𝑁 − (𝑣) ⊆ 𝑉 𝑣 ∈ 𝑉, |𝑁 − (𝑣)| ≥ 2 . Thus each hyperedge of CH(𝐷) groups all vertices that compete for the same target 𝑣 (i.e. all predators of 𝑣), provided there are at least two such vertices. Example 6.2.2 (Competition hypergraph CH(𝐷)). Let 𝐷 = (𝑉, 𝐴) be the directed graph with 𝑉 = {𝑎, 𝑏, 𝑐, 𝑑}, 𝐴 = {(𝑎, 𝑑), (𝑏, 𝑑), (𝑐, 𝑑), (𝑎, 𝑐)}. Compute in-neighborhoods: 𝑁 − (𝑎) = ∅, 𝑁 − (𝑏) = ∅, 𝑁 − (𝑐) = {𝑎}, 𝑁 − (𝑑) = {𝑎, 𝑏, 𝑐}. By definition, the hyperedge family of CH(𝐷) is 𝐸 = 𝑁 − (𝑣) | 𝑣 ∈ 𝑉, |𝑁 − (𝑣)| ≥ 2 = {𝑎, 𝑏, 𝑐} . Hence CH(𝐷) = (𝑉, 𝐸) has the single hyperedge {𝑎, 𝑏, 𝑐}, representing that 𝑎, 𝑏, 𝑐 compete for the same target 𝑑. 202

204.

Chapter 6. Applications of SuperHyperGraph Definition 6.2.3 ((Recall) Iterated powerset and flattening). Let 𝑉0 be a finite base set. Define the iterated powersets by P0 (𝑉0 ) := 𝑉0 , P 𝑘+1 (𝑉0 ) := P P 𝑘 (𝑉0 ) (𝑘 ≥ 0), where P(·) denotes the usual powerset. For each 𝑘 ≥ 0 define the flattening map flat 𝑘 : P 𝑘 (𝑉0 ) −→ P(𝑉0 ) recursively by flat0 (𝑥) := {𝑥} and, for 𝑘 ≥ 0, flat 𝑘+1 (𝑋) := Ø flat 𝑘 (𝑌 ) (𝑥 ∈ 𝑉0 ), for 𝑋 ∈ P 𝑘+1 (𝑉0 ) = P P 𝑘 (𝑉0 ) . 𝑌 ∈𝑋 Definition 6.2.4 (Competition 𝑛-SuperHyperGraph). [35] Let 𝐷 = (𝑉0 , 𝐴) be a finite directed graph, where 𝑉0 is the base vertex set and 𝐴 ⊆ 𝑉0 × 𝑉0 is the arc set. For a fixed integer 𝑛 ≥ 0, set 𝑉𝑛 := P𝑛 (𝑉0 ), so that each element 𝑆 ∈ 𝑉𝑛 is an 𝑛–supervertex (an 𝑛–fold iterated subset of 𝑉0 ). For 𝑆 ∈ 𝑉𝑛 , define its 𝑛–level in–neighborhood by n o 𝑁 𝑛− (𝑆) := 𝑇 ∈ 𝑉𝑛 ∃ 𝑢 ∈ flat𝑛 (𝑇), ∃ 𝑣 ∈ flat𝑛 (𝑆) with (𝑢, 𝑣) ∈ 𝐴 . The competition 𝑛–SuperHyperGraph of 𝐷 is the pair comp CompSuHG (𝑛) (𝐷) := 𝑉𝑛 , 𝐸 𝑛 where comp 𝐸𝑛 := 𝑁 𝑛− (𝑆) ⊆ 𝑉𝑛 , 𝑆 ∈ 𝑉𝑛 , |𝑁 𝑛− (𝑆)| ≥ 2 . Thus each (𝑛–level) competition superhyperedge 𝑁 𝑛− (𝑆) collects all 𝑛–supervertices 𝑇 whose flattened elements contain some predator 𝑢 of some prey 𝑣 in the flattened elements of 𝑆. For 𝑛 = 0 we have 𝑉0 itself and CompSuHG (0) (𝐷) reduces to the classical competition hypergraph CH(𝐷). Example 6.2.5 (Competition 1-SuperHyperGraph CompSuHG (1) (𝐷)). Let the base digraph 𝐷 = (𝑉0 , 𝐴) be given by 𝑉0 = {𝑎, 𝑏, 𝑐, 𝑑}, 𝐴 = {(𝑎, 𝑑), (𝑏, 𝑑), (𝑐, 𝑑), (𝑎, 𝑐)}. Fix 𝑛 = 1. Then 𝑉1 = P1 (𝑉0 ) = P (𝑉0 ), and for 𝑇 ∈ 𝑉1 we have flat1 (𝑇) = 𝑇. Choose the 1-supervertex (a subset of 𝑉0 ) 𝑆 := {𝑐, 𝑑} ∈ 𝑉1 . We compute its 1-level in-neighborhood: n 𝑁1− (𝑆) = 𝑇 ∈ 𝑉1 o ∃𝑢 ∈ 𝑇, ∃𝑣 ∈ 𝑆 with (𝑢, 𝑣) ∈ 𝐴 . Since 𝑆 = {𝑐, 𝑑} and 𝐴 contains arcs into 𝑐 from 𝑎 and into 𝑑 from 𝑎, 𝑏, 𝑐, we get {𝑢 ∈ 𝑉0 : ∃𝑣 ∈ 𝑆 with (𝑢, 𝑣) ∈ 𝐴} = {𝑎, 𝑏, 𝑐}. Therefore 𝑇 ∈ 𝑁1− (𝑆) holds exactly when 𝑇 contains at least one element of {𝑎, 𝑏, 𝑐}. Equivalently, 𝑁1− (𝑆) = { 𝑇 ⊆ 𝑉0 | 𝑇 ∩ {𝑎, 𝑏, 𝑐} ≠ ∅ }. 203

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[beta]

Chapter 6. Applications of SuperHyperGraph
In particular,
| 𝑁1− (𝑆) | = 24 − 21 = 16 − 2 = 14 ≥ 2
(the only subsets of 𝑉0 not in 𝑁1− (𝑆) are ∅ and {𝑑}). Hence 𝑁1− (𝑆) is a competition 1-superhyperedge, and
comp

CompSuHG (1) (𝐷) = (𝑉1 , 𝐸 1

)

has (at least) the superhyperedge
𝑁1− ({𝑐, 𝑑}) = { 𝑇 ⊆ 𝑉0 | 𝑇 ∩ {𝑎, 𝑏, 𝑐} ≠ ∅ }.
This superhyperedge groups all 1-supervertices (subsets) that contain some predator of 𝑐 or 𝑑.
As reference information, an overview of competition graphs, competition hypergraphs, and competition
𝑛-SuperHyperGraphs is provided in Table 6.2.
Model

Objects

Competition graph

Digraph 𝐷 = (𝑉, 𝐴)

Competition
[950–952]

Digraph 𝐷 = (𝑉, 𝐴)

hypergraph

Competition
𝑛SuperHyperGraph [35]

Digraph 𝐷 = (𝑉0 , 𝐴) and level-𝑛 supervertices 𝑉𝑛 = P𝑛 (𝑉0 )

Competition relation (edge / hyperedge /
superhyperedge)
Undirected edge {𝑥, 𝑦} exists iff ∃ 𝑣 ∈ 𝑉
such that (𝑥, 𝑣) ∈ 𝐴 and (𝑦, 𝑣) ∈ 𝐴 (two
vertices share a common out-neighbor).
Hyperedge is the in-neighborhood
𝑁 − (𝑣) = {𝑢 ∈ 𝑉 | (𝑢, 𝑣) ∈ 𝐴} for some
𝑣, included only when |𝑁 − (𝑣)| ≥ 2 (all
predators competing for the same target
𝑣).
Superhyperedge is 𝑁 𝑛− (𝑆) = {𝑇 ∈ 𝑉𝑛 |
∃𝑢 ∈ flat𝑛 (𝑇), ∃𝑣 ∈ flat𝑛 (𝑆) : (𝑢, 𝑣) ∈
𝐴}, included only when |𝑁 𝑛− (𝑆)| ≥ 2.

Table 6.2: Overview of competition graphs, competition hypergraphs, and competition 𝑛-SuperHyperGraphs.

6.3

Property SuperHyperGraphs

Property graphs represent entities as vertices and relationships as edges, both carrying key–value properties for
flexible, attributed graph modeling (cf. [953–955]). A Property HyperGraph annotates vertices and hyperedges
with attribute values, enabling constraint checking, classification, and reasoning over multiway relational
structures [41]. A Property n-SuperHyperGraph extends this labeling to n-supervertices and n-superedges,
supporting hierarchical attributes, constraints, and analyses across powerset levels effectively [41].
Definition 6.3.1 (Property HyperGraph). [41] Fix three (possibly infinite) sets
Σ (hyperedge–label alphabet),

𝐾 (property keys),

𝑆 (property values),

and let ⊥ ∉ 𝑆 be a distinguished symbol.
A Property HyperGraph is a quadruple
𝐻 = (𝑉, 𝐸, 𝜆, 𝜇)
satisfying:
• 𝑉 is a finite (or at most countable) set of vertices.
• 𝐸 is a finite family of nonempty subsets of 𝑉, i.e. 𝐸 ⊆ P (𝑉) \ {∅}; the elements of 𝐸 are called
hyperedges.
• 𝜆 : 𝐸 → Σ assigns a label to each hyperedge.
• 𝜇 : (𝑉 ∪ 𝐸) × 𝐾 → 𝑆 ∪ {⊥} is the property map; for 𝑥 ∈ 𝑉 ∪ 𝐸 and 𝑘 ∈ 𝐾 the value 𝜇(𝑥, 𝑘) = 𝑠 ∈ 𝑆
means that 𝑥 has property key 𝑘 with value 𝑠, while 𝜇(𝑥, 𝑘) = ⊥ means that 𝑥 carries no value for key 𝑘.
204

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Chapter 6. Applications of SuperHyperGraph
For each 𝑥 ∈ 𝑉 ∪ 𝐸 we define the keyset and value notation
keyset(𝑥) := { 𝑘 ∈ 𝐾 | 𝜇(𝑥, 𝑘) ≠ ⊥ },

val(𝑥, 𝑘) := 𝜇(𝑥, 𝑘)

(𝑘 ∈ keyset(𝑥)).

Definition 6.3.2 (Property 𝑛-SuperHyperGraph (Property SuperHyperGraph)).
nonempty base set and define the iterated powersets

P0 (𝑉0 ) := 𝑉0 ,
P 𝑘+1 (𝑉0 ) := P P 𝑘 (𝑉0 ) (𝑘 ≥ 0),

[41] Let 𝑉0 be a finite,

where P (·) denotes the usual powerset. Fix an integer 𝑛 ≥ 0.
As above, fix sets
Σ (superedge–label alphabet),

𝐾 (property keys),

𝑆 (property values),

and a distinguished symbol ⊥ ∉ 𝑆.
A Property 𝑛-SuperHyperGraph on 𝑉0 (or Property SuperHyperGraph of level 𝑛) is a quadruple

𝐻 (𝑛) = 𝑉 (𝑛) , 𝐸 (𝑛) , 𝜆, 𝜇
with:
• 𝑉 (𝑛) ⊆ P𝑛 (𝑉0 ), whose elements are called 𝑛-supervertices;

• 𝐸 (𝑛) ⊆ P 𝑉 (𝑛) \ {∅}, whose elements are called 𝑛-superedges;
• 𝜆 : 𝐸 (𝑛) → Σ is a superedge–labelling map;

• 𝜇 : 𝐷 (𝑛) × 𝐾 → 𝑆 ∪ {⊥} is a property map, where
𝐷 (𝑛) :=

𝑛
Ø


P 𝑘 (𝑉0 ) ∪ 𝐸 (𝑛) .

𝑘=0

For 𝑥 ∈ 𝐷 (𝑛) and 𝑘 ∈ 𝐾, the value 𝜇(𝑥, 𝑘) = 𝑠 ∈ 𝑆 means that 𝑥 carries property key 𝑘 with value 𝑠,
while 𝜇(𝑥, 𝑘) = ⊥ means that 𝑥 has no value for key 𝑘.
For each 𝑥 ∈ 𝐷 (𝑛) we write
keyset(𝑥) := { 𝑘 ∈ 𝐾 | 𝜇(𝑥, 𝑘) ≠ ⊥ },

val(𝑥, 𝑘) := 𝜇(𝑥, 𝑘)

(𝑘 ∈ keyset(𝑥)).

When 𝑛 = 1 and only the level–1 carriers and their superedges are used, 𝐻 (1) reduces to a Property HyperGraph;
when Σ is a singleton and 𝜇 ≡ ⊥, 𝐻 (𝑛) reduces to an ordinary 𝑛-SuperHyperGraph.
Example 6.3.3 (Property SuperHyperGraph for a hospital patient-care pathway (real-life)). A hospital patientcare pathway is an ordered sequence of clinical steps, departments, and decisions guiding diagnosis, treatment,
monitoring, and discharge for patients (cf. [956]). Let the base set 𝑉0 be a finite set of atomic care-events:
𝑉0 := {Triage, CT, Lab, Consult, Surgery, ICU, Discharge}.
Fix level 𝑛 = 1, so P1 (𝑉0 ) = P (𝑉0 ).
Define 1-supervertices (departments / care-units as bundles of events):
𝑣 ER := {Triage, Lab},

𝑣 Imaging := {CT},

𝑣 OR := {Surgery},

𝑣 Ward := {ICU, Discharge},

𝑉 (1) := {𝑣 ER , 𝑣 Imaging , 𝑣 OR , 𝑣 Ward } ⊆ P1 (𝑉0 ).
Define 1-superedges (multiway episodes linking several units):
𝑒 workup := {𝑣 ER , 𝑣 Imaging },

𝑒 operative := {𝑣 ER , 𝑣 OR , 𝑣 Ward },
205

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207.

Chapter 6. Applications of SuperHyperGraph 𝐸 (1) := {𝑒 workup , 𝑒 operative } ⊆ P (𝑉 (1) ) \ {∅}. Choose a label alphabet and property keys/values: Σ := {diagnostic, treatment}, 𝐾 := {capacity, risk, priority, SLA}, 𝑆 := R ≥0 ∪ {low, medium, high}. Let ⊥ ∉ 𝑆 be the “undefined” symbol. Define the superedge labels 𝜆 : 𝐸 (1) → Σ by 𝜆(𝑒 workup ) = diagnostic, 𝜆(𝑒 operative ) = treatment. Define the property map 𝜇 : (𝐷 (1) × 𝐾) → 𝑆 ∪ {⊥} on 𝐷 (1) = 𝑉0 ∪ P1 (𝑉0 ) ∪ 𝐸 (1) by specifying representative values (all unspecified pairs map to ⊥): 𝜇(𝑣 ER , capacity) = 40, 𝜇(𝑣 Imaging , capacity) = 12, 𝜇(𝑒 workup , SLA) = 2, 𝜇(𝑣 OR , capacity) = 6, 𝜇(𝑣 Ward , capacity) = 20, 𝜇(𝑒 operative , SLA) = 6, 𝜇(𝑒 workup , risk) = medium, 𝜇(𝑒 operative , risk) = high. Then 𝐻 (1) = (𝑉 (1) , 𝐸 (1) , 𝜆, 𝜇) is a Property 1-SuperHyperGraph. It models hospital care at two levels: atomic events (𝑉0 ), grouped units (supervertices in 𝑉 (1) ), and multiway episodes (superedges in 𝐸 (1) ), while 𝜇 attaches operational attributes (capacity, risk, SLA/priority) enabling constraint checks such as val(𝑒 operative , risk) = high ⇒ val(𝑣 OR , capacity) ≥ 1 and val(𝑒 operative , SLA) ≤ 8. 6.4 Knowledge SuperHyperGraphs Knowledge graphs are structured semantic networks representing entities and relationships, enabling integration, reasoning, and querying across heterogeneous data sources [957–960]. Knowledge graphs are being actively studied and applied across a wide range of fields, including chemistry, computer science, and medicine (cf. [961–964]). Fuzzy knowledge graphs [965–967] and directed knowledge graphs [968, 969] are known as related concepts. Moreover, in machine–learning domains, extensive research has also been conducted on knowledge graph embeddings [970–972] and related representation–learning methods. A knowledge hypergraph encodes entities as vertices and relational facts as hyperedges, representing structured, queryable knowledge bases in various domains [37,38,973,974]. A knowledge n-SuperHyperGraph lifts entities to iterated powerset supervertices, linking hierarchical superfacts as superhyperedges across abstraction levels in complex domains [975, 976]. Definition 6.4.1 (Knowledge hypergraph). (cf. [977]) Let 𝐸 be a finite set of entities and 𝑅 a finite set of relation symbols. For each 𝑟 ∈ 𝑅 let |𝑟 | ∈ N denote its arity (the number of arguments of 𝑟). The set of all (ground) candidate facts over (𝐸, 𝑅) is n 𝜏(𝐸, 𝑅) := 𝑟 (𝑒 1 , . . . , 𝑒 |𝑟 | ) o 𝑟 ∈ 𝑅, 𝑒 𝑖 ∈ 𝐸 (𝑖 = 1, . . . , |𝑟 |) . A world on (𝐸, 𝑅) is a subset 𝜏0 ⊆ 𝜏(𝐸, 𝑅), whose elements are interpreted as true facts. A knowledge hypergraph is a triple 𝐻 = (𝐸, 𝑅, 𝜏0 ), where 𝜏0 ⊆ 𝜏(𝐸, 𝑅) is a world on (𝐸, 𝑅). Each fact 𝑟 (𝑒 1 , . . . , 𝑒 |𝑟 | ) ∈ 𝜏0 is viewed as a (labelled) hyperedge that simultaneously links the entities 𝑒 1 , . . . , 𝑒 |𝑟 | . The underlying (unlabelled) hypergraph associated with 𝐻 has vertex set 𝐸 and hyperedge set n o 𝐸 𝐻 := {𝑒 1 , . . . , 𝑒 |𝑟 | } 𝑟 (𝑒 1 , . . . , 𝑒 |𝑟 | ) ∈ 𝜏0 . 206

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Chapter 6. Applications of SuperHyperGraph
Definition 6.4.2 (Knowledge 𝑛-SuperHyperGraph). [975, 976] Let 𝐸 0 be a finite base set of entities and let 𝑅
be a finite set of relation symbols with arity map
𝑟 ↦−→ |𝑟 | ∈ N

(𝑟 ∈ 𝑅).

For 𝑛 ∈ N0 define the iterated powersets of 𝐸 0 by
P0 (𝐸 0 ) := 𝐸 0 ,

P 𝑘+1 (𝐸 0 ) := P P 𝑘 (𝐸 0 )



(𝑘 ≥ 0),

where P(·) denotes the usual powerset.
A knowledge 𝑛-SuperHyperGraph (or knowledge SuperHyperGraph of level 𝑛) over (𝐸 0 , 𝑅) is a triple

KH (𝑛) = 𝑉, 𝑅, 𝜏0(𝑛) ,
where
• 𝑉 ⊆ P𝑛 (𝐸 0 ) is a finite set of 𝑛-superentities (or 𝑛-supervertices); each 𝑣 ∈ 𝑉 is a nested group of entities
obtained by applying the powerset operator 𝑛 times to 𝐸 0 ;
• 𝜏0(𝑛) is a set of true 𝑛-superfacts of the form
n
𝜏0(𝑛) ⊆ 𝑟 (𝑣 1 , . . . , 𝑣 |𝑟 | )

o
𝑟 ∈ 𝑅, 𝑣 𝑖 ∈ 𝑉 (𝑖 = 1, . . . , |𝑟 |) .

Each fact 𝑟 (𝑣 1 , . . . , 𝑣 |𝑟 | ) ∈ 𝜏0(𝑛) is interpreted as a higher–order, recursively nested relation between the
superentities 𝑣 1 , . . . , 𝑣 |𝑟 | .
The underlying (unlabelled) level-𝑛 SuperHyperGraph associated with KH (𝑛) has vertex set 𝑉 and hyperedge
set
n
o
(𝑛)
𝐸𝐻
:= {𝑣 1 , . . . , 𝑣 |𝑟 | } 𝑟 (𝑣 1 , . . . , 𝑣 |𝑟 | ) ∈ 𝜏0(𝑛) ⊆ P(𝑉).
For 𝑛 = 0 and 𝑉 = 𝐸 0 this reduces to a (labelled) knowledge hypergraph in the sense of the previous definition.
For 𝑛 ≥ 1 the construction yields a hierarchical, multi–level generalization based on the iterated powerset of
the base entity set 𝐸 0 .
Example 6.4.3 (Knowledge 1-SuperHyperGraph: Data Science Curriculum). Consider a small curriculum in
data science (cf. [978]). Let the base entity set be
𝐸 0 = { LinAlg, Calc, Prob, ML, DL },
where
• LinAlg = Linear Algebra,
• Calc = Calculus,
• Prob = Probability,
• ML = Machine Learning,
• DL = Deep Learning.
For 𝑛 = 1 we have
P0 (𝐸 0 ) = 𝐸 0 ,

P1 (𝐸 0 ) = P(𝐸 0 ).

Define the set of 1-superentities (supervertices) by

𝑉 := {LinAlg}, {Calc}, {Prob}, {ML}, {DL}, {LinAlg, Calc, Prob}, {ML, DL}
207

⊆ P1 (𝐸 0 ).

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Chapter 6. Applications of SuperHyperGraph
Thus each 𝑣 ∈ 𝑉 is a set of base courses, viewed as a superentity; for instance:
𝑣 found := {LinAlg, Calc, Prob}
is a “foundational knowledge cluster”, and
𝑣 adv := {ML, DL}
is an “advanced modeling cluster”.
Let 𝑅 be a set of relation symbols containing a single binary symbol
𝑟 prereq ∈ 𝑅,

|𝑟 prereq | = 2,

to be read as “is a prerequisite cluster for”.
We now specify the set of true 1-superfacts 𝜏0(1) by
𝜏0(1) :=

n



o
𝑟 prereq {LinAlg, Calc, Prob}, {ML} , 𝑟 prereq {ML}, {DL} , 𝑟 prereq {LinAlg, Calc, Prob}, {ML, DL} .

These facts encode the following higher–order statements:

• the foundational cluster {LinAlg, Calc, Prob} is a prerequisite for the course ML;
• the course ML is a prerequisite for DL;
• the same foundational cluster is also a prerequisite for the advanced cluster {ML, DL} as a whole.

The triple
KH (1) := 𝑉, 𝑅, 𝜏0(1)



is therefore a knowledge 1-SuperHyperGraph over (𝐸 0 , 𝑅) in the sense of the definition above: vertices are
nested groups of courses, and hyperedges (encoded by the facts in 𝜏0(1) ) represent higher–order prerequisite
relations between course clusters.
(1)
The underlying (unlabelled) level-1 SuperHyperGraph 𝐸 𝐻
has vertex set 𝑉 and hyperedge set

n
o
(1)
= {{LinAlg, Calc, Prob}, {ML}}, {{ML}, {DL}}, {{LinAlg, Calc, Prob}, {ML, DL}} ,
𝐸𝐻
obtained by forgetting the label 𝑟 prereq . This 1-SuperHyperGraph compactly encodes multi-course, multi-level
prerequisite structures in the curriculum.

6.5

Quantum Superhypergraph

Quantum theory describes physical systems using wavefunctions, operators, and probability amplitudes, explaining superposition, entanglement, measurement outcomes, and quantized energies (cf. [979, 980]). Quantum graphs model wave or quantum dynamics on metric graph edges using differential operators, spectra, and
boundary conditions at vertices [44, 45, 981]. Related concepts, such as quantum directed graphs [982, 983],
periodic quantum graphs [984, 985], and infinite quantum graphs [986, 987] are also known. A Quantum
HyperGraph assigns qubits to hypergraph vertices and controlled-phase operations to hyperedges, defining
an entangled hypergraph state in Hilbert-space [46, 988–990]. A Quantum SuperHyperGraph equips each
supervertex of an n-SuperHyperGraph with a qubit, using multi-qubit phase gates to encode entanglement
structure [47].
208

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Chapter 6. Applications of SuperHyperGraph Definition 6.5.1 (Quantum Graph). [44, 45, 981] A quantum graph is a metric graph 𝐺 = (𝑉, 𝐸, (𝐿 𝑒 )𝑒∈𝐸 ) (each edge 𝑒 is identified with an interval [0, 𝐿 𝑒 ]) together with a self-adjoint differential operator 𝐻 on the Hilbert space Ê 𝐿 2 (0, 𝐿 𝑒 ), H := 𝑒∈𝐸 such that on each edge 𝑒 the operator acts as a one-dimensional Schrödinger operator (𝐻𝜓)𝑒 (𝑥) = − 𝑑2 𝜓𝑒 (𝑥) + 𝑉𝑒 (𝑥)𝜓𝑒 (𝑥) 𝑑𝑥 2 (𝑥 ∈ (0, 𝐿 𝑒 )), and the edge-components are coupled at vertices Í by self-adjoint vertex boundary conditions (e.g. continuity at each vertex and a Kirchhoff/𝛿-type condition 𝑒∼𝑣 𝜕𝜈 𝜓𝑒 (𝑣) = 𝛼𝑣 𝜓(𝑣)). The spectrum and eigenfunctions of 𝐻 are called the spectrum and eigenstates of the quantum graph. Definition 6.5.2 (Quantum HyperGraph). [46, 988–990] Let 𝐻 = (𝑉, 𝐸) be a finite hypergraph with vertex set 𝑉 = {𝑣 1 , . . . , 𝑣 𝑛 }. Associate to each vertex 𝑣 𝑖 ∈ 𝑉 a qubit with Hilbert space H𝑖 C2 , and set H := 𝑛 Ì H𝑖 . 𝑖=1 Define the single–qubit state 1 |+⟩ := √ |0⟩ + |1⟩ , 2 |+⟩ ⊗𝑛 := 𝑛 Ì |+⟩𝑖 . 𝑖=1 For each hyperedge 𝑒 ∈ 𝐸, define the projector 𝑃𝑒 := 𝑛 Ì ( 𝑀𝑖(𝑒) , 𝑀𝑖(𝑒) := 𝑖=1 |1⟩⟨1| 𝑖 , 𝑣 𝑖 ∈ 𝑒, 𝐼𝑖 , 𝑣 𝑖 ∉ 𝑒, and the associated controlled–phase operator 𝐶 𝑍 𝑒 := 𝐼 H − 2𝑃𝑒 , where 𝐼 H is the identity on H . Then 𝐶 𝑍 𝑒 multiplies by −1 exactly those computational basis vectors in which all qubits indexed by vertices of 𝑒 are in state |1⟩. The quantum hypergraph state associated with 𝐻 is Ö |𝐻⟩ := 𝐶 𝑍 𝑒 |+⟩ ⊗𝑛 , 𝑒∈𝐸 where the product may be taken in any fixed order (all 𝐶 𝑍 𝑒 are diagonal and therefore commute). A Quantum HyperGraph is the pair QH := (𝐻, |𝐻⟩), consisting of the finite hypergraph 𝐻 and its associated quantum hypergraph state |𝐻⟩ ∈ H . Example 6.5.3 (Quantum HyperGraph for a three-qubit phase-entangled state). Consider the finite hypergraph 𝐻 = (𝑉, 𝐸), 𝑉 = {𝑣 1 , 𝑣 2 , 𝑣 3 }, 𝐸 = {𝑣 1 , 𝑣 2 , 𝑣 3 } . Thus there is a single hyperedge joining all three vertices. Associate to each vertex 𝑣 𝑖 a qubit with Hilbert space H𝑖 C2 , and set H := H1 ⊗ H2 ⊗ H3 C8 . Let 1 |+⟩ := √ |0⟩ + |1⟩ , 2 |+⟩ ⊗3 := |+⟩1 ⊗ |+⟩2 ⊗ |+⟩3 . 209

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211.

Chapter 6. Applications of SuperHyperGraph For the unique hyperedge 𝑒 = {𝑣 1 , 𝑣 2 , 𝑣 3 }, define 𝑃𝑒 := |1⟩⟨1| 1 ⊗ |1⟩⟨1| 2 ⊗ |1⟩⟨1| 3 , 𝐶 𝑍 𝑒 := 𝐼 H − 2𝑃𝑒 . The quantum hypergraph state associated with 𝐻 is then |𝐻⟩ := 𝐶 𝑍 𝑒 |+⟩ ⊗3 . In words, we begin with three independent qubits in the equal superposition state |+⟩ ⊗3 and apply a three-qubit controlled phase gate that flips the sign of the basis state |111⟩. The pair QH := (𝐻, |𝐻⟩) is a concrete Quantum HyperGraph: the hypergraph 𝐻 encodes the three-body interaction pattern, and |𝐻⟩ is the resulting entangled quantum state. Definition 6.5.4 (Quantum SuperHyperGraph). [47] Let SHG (𝑛) = (𝑉, 𝐸) be an 𝑛-SuperHyperGraph with finite 𝑛-supervertex set 𝑉 = {𝑣 1 , . . . , 𝑣 𝑚 } and 𝑛-superedge set 𝐸. Associate to each 𝑛-supervertex 𝑣 ∈ 𝑉 a qubit with Hilbert space H𝑣 C2 and define the total Hilbert space Ì H := H𝑣 . 𝑣 ∈𝑉 Set 1 |+⟩ := √ |0⟩ + |1⟩ , 2 |+⟩ ⊗𝑚 := Ì |+⟩𝑣 . 𝑣 ∈𝑉 For each 𝑛-superedge 𝑒 ∈ 𝐸, define the projector ( 𝑃𝑒 := Ì 𝑀𝑣(𝑒) , 𝑀𝑣(𝑒) := 𝑣 ∈𝑉 |1⟩⟨1| 𝑣 , 𝑣 ∈ 𝑒, 𝐼𝑣 , 𝑣 ∉ 𝑒, and the generalized controlled–phase operator 𝐶 𝑍 𝑒 := 𝐼 H − 2𝑃𝑒 . Thus 𝐶 𝑍 𝑒 multiplies by −1 exactly those computational basis vectors in which all qubits indexed by supervertices in 𝑒 are in state |1⟩. The quantum 𝑛-SuperHyperGraph state associated with SHG (𝑛) is Ö SHG (𝑛) := 𝐶 𝑍 𝑒 |+⟩ ⊗𝑚 . 𝑒∈𝐸 A Quantum SuperHyperGraph of level 𝑛 is the pair QSH (𝑛) := SHG (𝑛) , SHG (𝑛) , consisting of the 𝑛-SuperHyperGraph SHG (𝑛) and its associated quantum SuperHyperGraph state in H . For 𝑛 = 1 and when 𝑉 is a set of ordinary vertices, this construction reduces to a Quantum HyperGraph. Example 6.5.5 (Quantum SuperHyperGraph for two logical qubits built from four physical qubits). Let the base set of physical qubits be 𝑉0 = {𝑞 1 , 𝑞 2 , 𝑞 3 , 𝑞 4 }. We group them into two logical modules 𝑣 𝐴 := {𝑞 1 , 𝑞 2 }, 𝑣 𝐵 := {𝑞 3 , 𝑞 4 }, and define the level-1 supervertex set 𝑉 := 𝑣 𝐴, 𝑣 𝐵 ⊆ P1 (𝑉0 ) = P (𝑉0 ). 210

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Chapter 6. Applications of SuperHyperGraph
Model
Quantum Graph [44,
45, 981]

Underlying object
Metric graph (𝑉, 𝐸, (𝐿 𝑒 ))
(edges are intervals)

Quantum
HyperGraph [46, 988–990]

Finite hypergraph (𝑉, 𝐸) (hyperedges are subsets of vertices)

Quantum
𝑛SuperHyperGraph
[47]

𝑛-SuperHyperGraph (𝑉, 𝐸)
(vertices are 𝑛-level supervertices)

State space / dynamics
Hilbert
space
É
2 (0, 𝐿 );
𝐿
self𝑒
𝑒∈𝐸
adjoint operator on edges +
vertex boundary conditions
|𝑉 |
qubits;
hyperedgecontrolled phase gates 𝐶 𝑍 𝑒
produce a hypergraph state
|𝐻⟩
One qubit per 𝑛-supervertex;
multi-qubit phase gates per 𝑛superedge yield |SHG (𝑛) ⟩

Typical data encoded
Spectrum, eigenfunctions,
wave/quantum transport on
networks
Multi-body entanglement
pattern specified by hyperedges
Entanglement
among
hierarchical/coarse-grained
subsystems (supervertices)

Table 6.3: Concise overview of Quantum Graphs, Quantum HyperGraphs, and Quantum 𝑛-SuperHyperGraphs.
Consider the 1-SuperHyperGraph
SHG (1) = (𝑉, 𝐸),


𝐸 := 𝑒 ,

𝑒 := {𝑣 𝐴, 𝑣 𝐵 },

so there is a single superedge 𝑒 connecting the two supervertices 𝑣 𝐴 and 𝑣 𝐵 . This models a higher-level
interaction between the two logical modules {𝑞 1 , 𝑞 2 } and {𝑞 3 , 𝑞 4 }.
We now construct a Quantum SuperHyperGraph of level 1 based on SHG (1) . Assign to each supervertex 𝑣 ∈ 𝑉
a qubit with Hilbert space H𝑣  C2 and define
H := H𝑣𝐴 ⊗ H𝑣𝐵  C4 .
Let


1
|+⟩ := √ |0⟩ + |1⟩ ,
2

|+⟩ ⊗2 := |+⟩𝑣𝐴 ⊗ |+⟩𝑣𝐵 .

For the superedge 𝑒 = {𝑣 𝐴, 𝑣 𝐵 }, define
𝑃𝑒 := |1⟩⟨1| 𝑣𝐴 ⊗ |1⟩⟨1| 𝑣𝐵 ,

𝐶 𝑍 𝑒 := 𝐼 H − 2𝑃𝑒 ,

so that 𝐶 𝑍 𝑒 is a controlled-phase gate acting on the two logical qubits corresponding to the supervertices 𝑣 𝐴
and 𝑣 𝐵 .
The associated Quantum SuperHyperGraph state is
SHG (1)

:= 𝐶 𝑍 𝑒 |+⟩ ⊗2 .

The pair
QSH (1) := SHG (1) , SHG (1)



is a concrete Quantum SuperHyperGraph: the level-1 SuperHyperGraph SHG (1) records an interaction between
two modules (each module being a subset of physical qubits in 𝑉0 ), and the quantum state SHG (1) is the
entangled state of the corresponding two logical qubits. In this way, Quantum SuperHyperGraphs naturally
model entanglement between coarse-grained subsystems rather than only between individual physical qubits.
The overview of Quantum Graphs, Quantum HyperGraphs, and Quantum 𝑛-SuperHyperGraphs is presented
in Table 6.3.

6.6

SuperHyperGraph Containter

A hypergraph container is a selected vertex subset system capturing all independent sets while greatly reducing
combinatorial search complexity space(cf. [76, 78, 991, 992]). A SuperHyperGraph container is a family of nsupervertex subsets covering all independent supervertex configurations within hierarchical SuperHyperGraph
structures and dynamics [992].
211

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Chapter 6. Applications of SuperHyperGraph Definition 6.6.1 ((Recall) 𝑟-uniform 𝑛-SuperHyperGraph). Let 𝑉0 be a nonempty finite base set and let P0 (𝑉0 ) := 𝑉0 , P 𝑘+1 (𝑉0 ) := P P 𝑘 (𝑉0 ) (𝑘 ≥ 0), where P(·) denotes the usual powerset. A level-𝑛 SuperHyperGraph on 𝑉0 is a pair SHG (𝑛) := (𝑉, 𝐸), where ∅ ≠ 𝐸 ⊆ P∗ (𝑉) := P(𝑉) \ {∅}. ∅ ≠ 𝑉 ⊆ P𝑛 (𝑉0 ), Elements of 𝑉 are called 𝑛-supervertices and elements of 𝐸 are called 𝑛-superedges. For 𝑟 ∈ N, the level-𝑛 SuperHyperGraph SHG (𝑛) is called 𝑟-uniform if 𝐸 ⊆ { 𝑒 ⊆ 𝑉 | |𝑒| = 𝑟 }, that is, every 𝑛-superedge contains exactly 𝑟 𝑛-supervertices. Definition 6.6.2 (Degree, average degree, and degree measure). Let SHG (𝑛) = (𝑉, 𝐸) be an 𝑟-uniform 𝑛-SuperHyperGraph with |𝑉 | = 𝑁 and |𝐸 | ≥ 1. For 𝑣 ∈ 𝑉, the degree of 𝑣 is 𝑑 (𝑣) := { 𝑒 ∈ 𝐸 | 𝑣 ∈ 𝑒 } . The average degree of SHG (𝑛) is 𝑑 := 1 ∑︁ 𝑑 (𝑣). 𝑁 𝑣 ∈𝑉 For any subset 𝑆 ⊆ 𝑉, the degree measure of 𝑆 is  0,     𝜇(𝑆) := 1 ∑︁  𝑑 (𝑣),   𝑁𝑑  𝑣 ∈𝑆 𝑆 = ∅, 𝑆 ≠ ∅. Note that 0 ≤ 𝜇(𝑆) ≤ 1 for all 𝑆 ⊆ 𝑉. Definition 6.6.3 (Induced sub-𝑛-SuperHyperGraph and edge count). Let SHG (𝑛) = (𝑉, 𝐸) be an 𝑟-uniform 𝑛-SuperHyperGraph. For any 𝑆 ⊆ 𝑉, the induced sub-𝑛-SuperHyperGraph on 𝑆 is SHG (𝑛) [𝑆] := 𝑆, 𝐸 [𝑆] , 𝐸 [𝑆] := { 𝑒 ∈ 𝐸 | 𝑒 ⊆ 𝑆 }. We write 𝑒(𝑆) := |𝐸 [𝑆] | for the number of 𝑛-superedges entirely contained in 𝑆. Definition 6.6.4 (Independent set in an 𝑛-SuperHyperGraph). Let SHG (𝑛) = (𝑉, 𝐸) be an 𝑟-uniform 𝑛SuperHyperGraph. A set 𝐼 ⊆ 𝑉 is called independent if it spans no 𝑛-superedges, i.e. 𝐸 [𝐼] = ∅ ⇐⇒ 𝑒(𝐼) = 0. Definition 6.6.5 (SuperHyperGraph container family). [992] Let SHG (𝑛) = (𝑉, 𝐸) be an 𝑟-uniform 𝑛SuperHyperGraph with average degree 𝑑 and degree measure 𝜇 as in Definition 6.6.2. A family C ⊆ P(𝑉) is called a container family (or a family of 𝑛-SuperHyperGraph containers) for SHG (𝑛) if the following two conditions hold. • Covering of independent sets. Every independent set 𝐼 ⊆ 𝑉 satisfies ∃𝐶 ∈ C such that 212 𝐼 ⊆ 𝐶.

#p298
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214.

Chapter 6. Applications of SuperHyperGraph • Smallness of containers. There exist fixed parameters 𝜀 ∈ (0, 1), 𝛼 ∈ (0, 1), such that for every 𝐶 ∈ C one has both 𝜇(𝐶) ≤ 𝛼 𝑒(𝐶) ≤ (1 − 𝜀) |𝐸 |. and In other words, every independent set of the 𝑟-uniform 𝑛-SuperHyperGraph is contained in at least one container 𝐶 ∈ C, and each container is “small” both in degree measure (it occupies at most an 𝛼-fraction of the total degree mass) and in the number of 𝑛-superedges it spans (it contains at most a (1 − 𝜀)-fraction of all 𝑛-superedges). For 𝑛 = 0 and 𝑉 ⊆ 𝑉0 this notion reduces to the usual hypergraph container family on an 𝑟-uniform hypergraph. Example 6.6.6 (SuperHyperGraph container: curriculum track design). We now describe a container family for a 2-SuperHyperGraph modeling university programme tracks built from course modules. Let 𝑉0 be a finite base set of courses and let 𝑃1 (𝑉0 ) := 𝑃(𝑉0 ), 𝑃2 (𝑉0 ) := 𝑃 𝑃(𝑉0 ) be the first and second iterated powersets. Consider three 2-supervertices 𝑣 found , 𝑣 AI , 𝑣 DS ∈ 𝑃2 (𝑉0 ), defined informally as follows. • 𝑣 found is a “foundation” track, consisting of a single core module (e.g. mathematics plus introductory programming). • 𝑣 AI is an AI-oriented track, containing the foundation module together with AI-related and data-science modules. • 𝑣 DS is a data-science track, combining the foundation module with data-science oriented modules. We form the 2-SuperHyperGraph SHG (2) := (𝑉, 𝐸), where 𝑉 := {𝑣 found , 𝑣 AI , 𝑣 DS } ⊆ 𝑃2 (𝑉0 ), and the 2-superedges are 𝑒 1 := {𝑣 found , 𝑣 AI }, 𝑒 2 := {𝑣 found , 𝑣 DS }, 𝑒 3 := {𝑣 AI , 𝑣 DS }, so that 𝐸 := {𝑒 1 , 𝑒 2 , 𝑒 3 }. This is a 2-uniform 2-SuperHyperGraph, since each 𝑒 𝑖 contains exactly two 2-supervertices. Degree, average degree, and degree measure. Each 2-supervertex lies in exactly two 2-superedges, so 𝑑 𝑣 found = 𝑑 𝑣 AI = 𝑑 𝑣 DS = 2. Hence 𝑁 := |𝑉 | = 3, ∑︁ 𝑑 (𝑣) = 2 + 2 + 2 = 6, 𝑣 ∈𝑉 and the average degree is 𝑑 = 6 1 ∑︁ 𝑑 (𝑣) = = 2. 𝑁 𝑣 ∈𝑉 3 213

215.

Chapter 6. Applications of SuperHyperGraph Thus 𝑁 𝑑 = 3 · 2 = 6, and for any nonempty 𝑆 ⊆ 𝑉 the degree measure is 1 ∑︁ 1 ∑︁ 𝑑 (𝑣) = 𝑑 (𝑣). 𝑁 𝑑 𝑣 ∈𝑆 6 𝑣 ∈𝑆 𝜇(𝑆) = Independent sets. A subset 𝐼 ⊆ 𝑉 is independent if it spans no 2-superedge, i.e. if 𝑒(𝐼) = 0. Since every pair of distinct 2-supervertices forms a 2-superedge (the structure is a “triangle” on 𝑉), any independent set 𝐼 can contain at most one vertex. Therefore the independent sets are exactly 𝐼 ∈ ∅, {𝑣 found }, {𝑣 AI }, {𝑣 DS } . Container family. Define 𝐶found := {𝑣 found }, 𝐶AI := {𝑣 AI }, 𝐶DS := {𝑣 DS }, and set C := {𝐶found , 𝐶AI , 𝐶DS } ⊆ 𝑃(𝑉). We verify that C is a container family for SHG (2) in the sense of Definition 6.6.5. (1) Covering of independent sets. Each nonempty independent set is equal to one of the three singletons above, and the empty set ∅ is contained in every container. Hence for every independent 𝐼 there exists 𝐶 ∈ C with 𝐼 ⊆ 𝐶. (2) Smallness of containers. For each container we have 1 1 2 1 𝜇 𝐶found = 𝑑 𝑣 found = · 2 = = , 6 6 6 3 and similarly 1 𝜇 𝐶AI = 𝜇 𝐶DS = . 3 Moreover, each container is a singleton, so it cannot contain a 2-superedge as a subset. Thus 𝑒 𝐶found = 𝑒 𝐶AI = 𝑒 𝐶DS = 0. Since |𝐸 | = 3, we choose 𝜀 := 1 , 2 𝛼 := Then (1 − 𝜀)|𝐸 | = and we have 𝑒(𝐶) = 0 ≤ 1− 1 . 2 1 3 ·3 = , 2 2 3 = (1 − 𝜀)|𝐸 | 2 for all 𝐶 ∈ C. Furthermore, 𝜇(𝐶) = 1 1 ≤ =𝛼 3 2 for all 𝐶 ∈ C. Hence C satisfies the smallness conditions. The 2-supervertices represent hierarchical curriculum patterns: each 𝑣 ∈ 𝑉 is a family of course modules forming a programme track (e.g. foundation, AI-focused, or data-science focused). The 2-superedges encode administrative couplings between tracks (for example, shared committees or accreditation constraints). Independent sets are collections of tracks that are not jointly constrained, so at most one track can be chosen freely at a time. The three containers {𝑣 found }, {𝑣 AI }, and {𝑣 DS } summarize all independent choices of higher-level programme configurations in this toy model. 214

#p213

216.

Chapter 6. Applications of SuperHyperGraph 6.7 SuperHyperGraph-Based Food Web A food web is an ecological network showing who eats whom among species, capturing energy flow and trophic interactions dynamically [943, 993, 994]. A graph-based food web models species as vertices and predator–prey relations as directed edges in a digraph for network analysis. A SuperHyperGraph-based food web uses n-supervertices from iterated powersets of species, encoding hierarchical, overlapping predator–prey groupings as superedges and contexts [80]. Definition 6.7.1 (SuperHyperGraph-Based Food Web (Food 𝑛-SuperHyperWeb)). [80] Let 𝐺 = (𝑉0 , 𝐸 0 ) be a Food Web, that is, a finite directed graph whose vertices are species and whose arcs encode predator–prey relations: (𝑢, 𝑣) ∈ 𝐸 0 ⇐⇒ species 𝑢 preys upon species 𝑣, with no self-loops and no parallel arcs. For each predator 𝑢 ∈ 𝑉0 define its prey set 𝑃(𝑢) := { 𝑣 ∈ 𝑉0 | (𝑢, 𝑣) ∈ 𝐸 0 }. Fix an integer 𝑛 ∈ N0 and let P 𝑛 (𝑉0 ) denote the 𝑛-fold iterated powerset of 𝑉0 as in Definition 2.2.1. Set 𝑉𝑛 := P 𝑛 (𝑉0 ), and for each 𝑢 ∈ 𝑉0 with 𝑃(𝑢) ≠ ∅ define the 𝑛-superedge 𝑒 𝑢(𝑛) := P 𝑛 𝑃(𝑢) ⊆ P 𝑛 (𝑉0 ) = 𝑉𝑛 . Thus each 𝑒 𝑢(𝑛) is a nonempty subset of 𝑉𝑛 , hence 𝑒 𝑢(𝑛) ∈ P∗ (𝑉𝑛 ), where P∗ (𝑉𝑛 ) := P (𝑉𝑛 ) \ {∅}. Define 𝐸 𝑛 := 𝑒 𝑢(𝑛) 𝑢 ∈ 𝑉0 , 𝑃(𝑢) ≠ ∅ ⊆ P∗ (𝑉𝑛 ). The pair 𝐹 (𝑛) := (𝑉𝑛 , 𝐸 𝑛 ) is called the Food 𝑛-SuperHyperWeb or SuperHyperGraph-Based Food Web of level 𝑛 associated with the Food Web 𝐺. By construction, ∅ ≠ 𝐸 𝑛 ⊆ P∗ (𝑉𝑛 ), ∅ ≠ 𝑉𝑛 ⊆ P 𝑛 (𝑉0 ), so 𝐹 (𝑛) is an 𝑛-SuperHyperGraph on the base set 𝑉0 in the sense used throughout this work. Moreover, let flat𝑛 be the full-flattening operator on P 𝑛 (𝑉0 ) (as in the definition of the competition 𝑛SuperHyperGraph). Applying flat𝑛 elementwise to each 𝑛-superedge 𝑒 𝑢(𝑛) and taking the union yields exactly the prey set 𝑃(𝑢): Ø flat𝑛 (𝑋) = 𝑃(𝑢). (𝑛) 𝑋∈𝑒𝑢 In this sense, the usual Food Hypergraph (with hyperedges 𝑃(𝑢), 𝑢 ∈ 𝑉0 ) and the original directed Food Web 𝐺 appear as flattened shadows of the SuperHyperGraph-based model 𝐹 (𝑛) . Example 6.7.2 (Coastal bay ecosystem as a Food 1-SuperHyperWeb). Consider a simplified coastal bay with the following five species: 𝑉0 := {Grass, Shrimp, Herring, Seal, Shark}, where Grass is a primary producer (seagrass or microalgae), Shrimp is a small benthic consumer, Herring is a small pelagic fish, Seal is a marine mammal, and Shark is a top predator. The predator–prey relations in the underlying Food Web 𝐺 = (𝑉0 , 𝐸 0 ) are: 𝐸 0 := {(Shrimp, Grass), (Herring, Shrimp), (Seal, Herring), (Shark, Seal), (Shark, Herring)}. 215

217.

Chapter 6. Applications of SuperHyperGraph For instance, (Shrimp, Grass) ∈ 𝐸 0 means that shrimp graze on seagrass, and (Shark, Seal) ∈ 𝐸 0 means that sharks prey on seals. For each predator 𝑢 ∈ 𝑉0 , its prey set 𝑃(𝑢) ⊆ 𝑉0 is 𝑃(Shrimp) = {Grass}, 𝑃(Seal) = {Herring}, 𝑃(Herring) = {Shrimp}, 𝑃(Shark) = {Seal, Herring}, and 𝑃(Grass) = ∅ since Grass is a primary producer. We now construct the Food 1-SuperHyperWeb 𝐹 (1) = (𝑉1 , 𝐸 1 ) associated with this Food Web, using Definition 2.2.1 and the SuperHyperGraph-Based Food Web construction. First, the level-1 vertex set is the powerset 𝑉1 := P 1 (𝑉0 ) = P (𝑉0 ), so a 1-supervertex is any subset of species, for example {Grass, Shrimp} or {Seal, Shark}. Intuitively, such a 1-supervertex represents a group of species that we consider jointly (e.g. a group of prey or a combined foraging guild). For each predator 𝑢 ∈ 𝑉0 with nonempty prey set 𝑃(𝑢), the 1-superedge is the powerset of its prey: 𝑒 𝑢(1) := P 1 (𝑃(𝑢)) = P (𝑃(𝑢)) ⊆ P (𝑉0 ) = 𝑉1 . We now compute these 1-superedges explicitly. (1) For Shrimp we have 𝑃(Shrimp) = {Grass}, so (1) 𝑒 Shrimp = P {Grass} = ∅, {Grass} . (2) For Herring we have 𝑃(Herring) = {Shrimp}, hence (1) 𝑒 Herring = P {Shrimp} = ∅, {Shrimp} . (3) For Seal we have 𝑃(Seal) = {Herring}, hence (1) 𝑒 Seal = P {Herring} = ∅, {Herring} . (4) For Shark we have 𝑃(Shark) = {Seal, Herring}, so (1) 𝑒 Shark = P {Seal, Herring} = ∅, {Seal}, {Herring}, {Seal, Herring} . Collecting all nonempty 1-superedges gives the edge set (1) (1) (1) (1) 𝐸 1 := 𝑒 Shrimp , 𝑒 Herring , 𝑒 Seal , 𝑒 Shark ⊆ P∗ (𝑉1 ), and the Food 1-SuperHyperWeb is 𝐹 (1) := (𝑉1 , 𝐸 1 ). In this coastal-bay interpretation, each 1-supervertex 𝑋 ∈ 𝑉1 is a prey group (a set of species viewed together), while each 1-superedge 𝑒 𝑢(1) represents all possible prey-group configurations formed from the predator 𝑢’s (1) prey list. For example, 𝑒 Shark contains: 216

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[beta]

Chapter 6. Applications of SuperHyperGraph
• {Seal, Herring}: shark foraging on both seals and herring together,
• {Seal} or {Herring}: shark feeding predominantly on just one prey type,
• ∅: a “no-catch” or inactive-foraging configuration.
If we denote by flat1 the full-flattening operator on P (𝑉0 ) (so that flat1 (𝑋) = 𝑋 for any 𝑋 ⊆ 𝑉0 ), then for each
predator 𝑢 we can recover its original prey set as
Ø
Ø
flat1 (𝑋) =
𝑋 = 𝑃(𝑢).
(1)

𝑋∈ P ( 𝑃 (𝑢) )

𝑋∈𝑒𝑢

Thus the usual Food Hypergraph (whose hyperedges are the prey sets 𝑃(𝑢)) and the directed Food Web 𝐺
appear as flattened shadows of the richer SuperHyperGraph-based food-web model 𝐹 (1) , which captures not
only “who eats whom” but also how an apex predator such as Shark may dynamically combine or switch among
different prey groups in a realistic coastal ecosystem.

6.8

Crystal SuperHyperGraph in material sciences

A crystal graph represents atoms as vertices and bonds as edges in a periodic lattice, capturing coordination connectivity for analysis [83, 995, 996]. A crystal SuperHyperGraph organizes atoms and motifs into
iterated powerset supervertices and superedges, modeling hierarchical coordination patterns and overlapping
environments [85].
Definition 6.8.1 (Crystal 𝑛-SuperHyperGraph). [85] Let 𝐶 be a periodic crystal structure with atom set
𝑉0 = {𝑣 1 , . . . , 𝑣 𝑁 }
in a unit cell and lattice Λ. For each integer 𝑘 ≥ 0, define the iterated powerset of 𝑉0 by

P0 (𝑉0 ) := 𝑉0 ,
P𝑘+1 (𝑉0 ) := P P𝑘 (𝑉0 ) ,
where P (𝑋) denotes the powerset of 𝑋.
Fix 𝑛 ∈ N0 . A Crystal 𝑛-SuperHyperGraph is a pair

CSHT(𝑛) := 𝑉 (𝑛) , 𝐸 (𝑛) ,
where
∅ ≠ 𝑉 (𝑛) ⊆ P𝑛 (𝑉0 )

and

∅ ≠ 𝐸 (𝑛) ⊆ P (𝑉 (𝑛) ) \ {∅}.

The elements of 𝑉 (𝑛) are called 𝑛-supervertices, and the elements of 𝐸 (𝑛) are called 𝑛-superedges. The
incidence relation between 𝑛-supervertices and 𝑛-superedges is given by set membership:
(𝑣, 𝑒) is incident

⇐⇒

𝑣 ∈ 𝑉 (𝑛) , 𝑒 ∈ 𝐸 (𝑛) , 𝑣 ∈ 𝑒.

Each 𝑛-supervertex 𝑣 ∈ 𝑉 (𝑛) represents a (possibly nested) cluster of atoms or lower-level motifs of the crystal
𝐶 across 𝑛 powerset layers, and each 𝑛-superedge 𝑒 ∈ 𝐸 (𝑛) collects a finite nonempty family of such clusters
that interact structurally (e.g., overlapping coordination environments).
In particular:
• for 𝑛 = 0, CSHT(0) reduces to the usual Crystal Graph on the atom set 𝑉0 ;
• for 𝑛 = 1, CSHT(1) recovers the standard Crystal HyperGraph, whose hyperedges encode local coordination motifs in the crystal lattice.
Thus every Crystal 𝑛-SuperHyperGraph is an 𝑛-SuperHyperGraph built over the base atom set 𝑉0 of the crystal
𝐶.
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Chapter 6. Applications of SuperHyperGraph Example 6.8.2 (Crystal 2-SuperHyperGraph for a perovskite-like unit). Consider a simplified perovskite-type unit cell (cf. [997]) with one 𝐴-site cation, one 𝐵-site cation, and three oxygen atoms. Let the base atom set be 𝑉0 = {𝐴1 , 𝐵1 , 𝑂 1 , 𝑂 2 , 𝑂 3 }. The first iterated powerset is P1 (𝑉0 ) = P (𝑉0 ), and the second iterated powerset is P2 (𝑉0 ) = P P (𝑉0 ) . Within P1 (𝑉0 ) we single out two local coordination motifs: 𝑀 𝐴 := {𝐴1 , 𝑂 1 , 𝑂 2 , 𝑂 3 } 𝑀 𝐵 := {𝐵1 , 𝑂 1 , 𝑂 2 , 𝑂 3 } (the 𝐴-centered coordination polyhedron), (the 𝐵-centered coordination polyhedron). Both 𝑀 𝐴 and 𝑀 𝐵 are ordinary subsets of 𝑉0 and hence elements of P1 (𝑉0 ). We now pass to the second powerset P2 (𝑉0 ). Define three 2-supervertices by 𝑣 1 := {𝑀 𝐴 }, 𝑣 2 := {𝑀 𝐵 }, 𝑣 3 := {𝑀 𝐴, 𝑀 𝐵 }, so that 𝑣 1 , 𝑣 2 , 𝑣 3 ∈ P2 (𝑉0 ) = P (P (𝑉0 )). Set 𝑉 (2) := {𝑣 1 , 𝑣 2 , 𝑣 3 } ⊆ P2 (𝑉0 ). We interpret 𝑣 1 as the 𝐴-centered motif, 𝑣 2 as the 𝐵-centered motif, and 𝑣 3 as a “layer” or combined structural unit that simultaneously contains both motifs (for example, an 𝐴𝐵𝑂 3 sheet in a layered crystal). Next, define two 2-superedges as 𝑒 1 := {𝑣 1 , 𝑣 3 }, 𝑒 2 := {𝑣 2 , 𝑣 3 }. Clearly 𝑒 1 , 𝑒 2 ∈ P (𝑉 (2) ) \ {∅}, so if we set 𝐸 (2) := {𝑒 1 , 𝑒 2 }, then CSHT(2) := 𝑉 (2) , 𝐸 (2) is a Crystal 2-SuperHyperGraph in the sense of Definition 6.8.1. The incidence is given by set membership: 𝑣 1 ∈ 𝑒1 , 𝑣 3 ∈ 𝑒1 , 𝑣 2 ∈ 𝑒2 , 𝑣 3 ∈ 𝑒2 . Chemically, this structure can be read as follows. • The 2-supervertices 𝑣 1 and 𝑣 2 encode the 𝐴- and 𝐵-centered coordination polyhedra as first-level motifs. • The 2-supervertex 𝑣 3 encodes a higher-level structural unit (a local 𝐴𝐵𝑂 3 layer) that contains both motifs. • The 2-superedges 𝑒 1 and 𝑒 2 record that the combined layer 𝑣 3 is structurally coupled with each of its component motifs (𝑣 1 and 𝑣 2 ), representing, for instance, shared oxygen atoms and cooperative distortions. Thus CSHT(2) provides a simple Crystal 2-SuperHyperGraph which organizes atoms, coordination polyhedra, and their composite layer into two iterated powerset levels. 218

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Chapter 6. Applications of SuperHyperGraph 6.9 SuperHyperGraph Neural Networks AI has recently become a highly prominent concept, exerting a substantial and positive influence on many aspects of human society. Machine learning and neural-network research have attracted significant attention in modern artificial-intelligence studies [998–1003]. A Graph Neural Network learns vector representations of graph nodes or edges by aggregating and transforming information from neighborhood structures [1004, 1005]. Related variants of Graph Neural Networks are also well known, including Fuzzy Graph Neural Networks [1006,1007], Neutrosophic Graph Neural Networks [1005], Molecular Graph Neural Networks [1008–1010], and Directed Graph Neural Networks [1011, 1012]. A HyperGraph Neural Network generalizes GNNs by propagating features through hyperedges, capturing higher-order relationships among multiple nodes simultaneously within hypergraphs [4,1013–1018]. A SuperHyperGraph Neural Network extends HGNNs to n-SuperHyperGraphs, learning representations over iterated powerset vertices and hierarchical superedges across multiple levels [12, 91, 1019–1021]. Definition 6.9.1 (SuperHyperGraph Neural Network (SHGNN)). [91] Let 𝑉0 be a finite base vertex set. Define the iterated powersets by P0 (𝑉0 ) := 𝑉0 , P 𝑘+1 (𝑉0 ) := P P 𝑘 (𝑉0 ) (𝑘 ≥ 0), where P(·) denotes the usual powerset, and P∗ (𝑋) := P(𝑋) \ {∅}. An 𝑛-SuperHyperGraph on 𝑉0 is a pair SHG (𝑛) = 𝑉 (𝑛) , 𝐸 (𝑛) , with ∅ ≠ 𝑉 (𝑛) ⊆ P𝑛 (𝑉0 ), ∅ ≠ 𝐸 (𝑛) ⊆ P∗ 𝑉 (𝑛) , whose elements are called 𝑛-supervertices and 𝑛-superedges, respectively. For each 𝑘 ≥ 0 the flattening map flat 𝑘 : P 𝑘 (𝑉0 ) −→ P(𝑉0 ) is defined recursively by flat0 (𝑥) := {𝑥} and, for 𝑘 ≥ 0, flat 𝑘+1 (𝑋) := Ø flat 𝑘 (𝑌 ) (𝑥 ∈ 𝑉0 ), for 𝑋 ∈ P 𝑘+1 (𝑉0 ) = P P 𝑘 (𝑉0 ) . 𝑌 ∈𝑋 Given the 𝑛-SuperHyperGraph SHG (𝑛) = (𝑉 (𝑛) , 𝐸 (𝑛) ), we flatten each 𝑛-supervertex 𝑣 ∈ 𝑉 (𝑛) to a base-level vertex set flat𝑛 (𝑣) ⊆ 𝑉0 , and each 𝑛-superedge 𝑒 ∈ 𝐸 (𝑛) , which is a nonempty subset of 𝑉 (𝑛) , to Ø Flat𝑛 (𝑒) := flat𝑛 (𝑣) ⊆ 𝑉0 . 𝑣 ∈𝑒 The expanded hypergraph associated with SHG (𝑛) is n 𝐻 ′ := (𝑉0 , 𝐸 ′ ), 𝐸 ′ := Flat𝑛 (𝑒) o 𝑒 ∈ 𝐸 (𝑛) , Flat𝑛 (𝑒) ≠ ∅ . Example 6.9.2 (SuperHyperGraph Neural Network for curriculum recommendation). A curriculum recommendation suggests personalized courses and learning sequences based on goals, prerequisites, skills gaps, constraints, and predicted learning outcomes (cf. [1022, 1023]). Consider a small curriculum with the following undergraduate courses as base vertices: 𝑉0 := {Alg, Lin, DL, DB}, where Alg = Algorithms, Lin = Linear Algebra, DL = Deep Learning, DB = Databases. We form a 1-SuperHyperGraph SHG (1) = (𝑉 (1) , 𝐸 (1) ) on 𝑉0 as follows. The 1-supervertices are modules, each being a subset of courses: 𝑉 (1) := {𝑣 1 , 𝑣 2 , 𝑣 3 }, 𝑣 1 := {Alg, Lin}, 𝑣 2 := {Lin, DB}, 𝑣 3 := {Alg, DL, DB}. 219

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The 1-superedges are study programmes grouping related modules:
𝐸 (1) := {𝑒 1 , 𝑒 2 },

𝑒 1 := {𝑣 1 , 𝑣 3 }, 𝑒 2 := {𝑣 2 }.

Thus 𝑒 1 represents an “AI & Systems” programme (mixing Alg, Lin, DL, DB via 𝑣 1 , 𝑣 3 ), while 𝑒 2 is a “Data
Systems” programme.
To apply a SuperHyperGraph Neural Network, we first flatten the 1-superedges to obtain a hypergraph on the
base courses. For 𝑣 ∈ 𝑉 (1) we set
Ø
flat1 (𝑣) = 𝑣 ⊆ 𝑉0 ,
Flat1 (𝑒) :=
flat1 (𝑣) ⊆ 𝑉0 .
𝑣 ∈𝑒

Hence
Flat1 (𝑒 1 ) = 𝑣 1 ∪ 𝑣 3 = {Alg, Lin, DL, DB},

Flat1 (𝑒 2 ) = 𝑣 2 = {Lin, DB}.

The expanded hypergraph is
𝐻 ′ = (𝑉0 , 𝐸 ′ ),

𝐸 ′ := {Flat1 (𝑒 1 ), Flat1 (𝑒 2 )}.

Let 𝑚 := |𝑉0 | = 4 and 𝑝 := |𝐸 ′ | = 2. We index 𝑉0 = {𝑣 1(0) , . . . , 𝑣 4(0) } = {Alg, Lin, DL, DB} and 𝐸 ′ =
{𝑒 1′ , 𝑒 2′ } = {Flat1 (𝑒 1 ), Flat1 (𝑒 2 )}. The incidence matrix of 𝐻 ′ is
1
©
1

𝐻′ = 
1
«1

0
ª
1®
®,
0®
1¬

where row 𝑖 corresponds to course 𝑣 𝑖(0) and column 𝑗 to hyperedge 𝑒 ′𝑗 .
Suppose each course has a feature vector in R𝑑 (e.g. difficulty level, pass rate, credit weight, topical category).
Collecting them row-wise gives the input feature matrix
𝑥⊤
ª
© Alg
𝑥⊤ ®
𝑋 =  Lin
.
⊤ ®
 𝑥DL
®
⊤
«𝑥DB ¬

𝑋 ∈ R4×𝑑 ,

Choose a positive weight function 𝑤 : 𝐸 ′ → R>0 , e.g. 𝑤(𝑒 1′ ) = 1.0, 𝑤(𝑒 2′ ) = 0.8, and construct the degree
matrices 𝐷 𝑉 , 𝐷 𝐸 as in the SHGNN definition. For a learnable hyperedge-weight matrix 𝑊 ∈ R2×2 , parameter
matrix Θ ∈ R𝑑×𝑐 , and activation 𝜎, a single SHGNN layer produces


−1 ′⊤ −1/2
𝑌 := 𝜎 𝐷 𝑉−1/2 𝐻 ′ 𝑊 𝐷 𝐸
𝐻 𝐷 𝑉 𝑋 Θ ∈ R4×𝑐 ,
where the 𝑖-th row of 𝑌 is the learned representation of course 𝑣 𝑖(0) informed by all multi-course programmes
that contain it.
In a practical system, these SHGNN embeddings can be used for tasks such as course recommendation, prerequisite prediction, or early-warning classification of at-risk students, while the 1-SuperHyperGraph explicitly
encodes the hierarchical structure (course ⊂ module ⊂ programme) guiding the message passing.

6.10

Semantic SuperHyperGraphs in Psychology

A semantic graph represents entities as vertices and labeled edges as typed relations, enabling meaningaware queries and inference [48, 1024, 1025]. A semantic hypergraph uses hyperedges linking several entities
within one relation instance, capturing multi-entity interactions and contextual constraints [49, 1026, 1027].
A semantic n-SuperHyperGraph organizes entities into iterated powerset levels, with superedges connecting
nested semantic groups across abstraction layers [50].
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Definition 6.10.1 (Semantic 𝑛-SuperHyperGraph). [50] Let
𝐺 = (𝑉, 𝐸, 𝐿, ℓ, 𝑤)
be a Semantic Graph, where 𝑉 is a finite concept set, 𝐸 ⊆ 𝑉 × 𝑉 is the directed edge set, 𝐿 is a finite set of
relation labels, ℓ : 𝐸 → 𝐿 assigns each edge its semantic relation type, and 𝑤 : 𝐸 → [0, 1] assigns each edge
a relation strength or confidence.
Let
𝐻 = (𝑉, 𝐸 𝐻 , 𝐿 𝐻 , ℓ𝐻 , 𝑤 𝐻 )
be the induced Semantic HyperGraph, where 𝐸 𝐻 ⊆ P (𝑉) \ {∅} is the family of semantic hyperedges,
𝐿 𝐻 = P (𝐿) \ {∅} is the hyperedge–label set, ℓ𝐻 : 𝐸 𝐻 → 𝐿 𝐻 aggregates edge labels on each hyperedge,
and 𝑤 𝐻 : 𝐸 𝐻 → [0, 1] assigns each hyperedge a weight (e.g. maximal edge weight inside the hyperedge).
For an integer 𝑛 ≥ 1, the Semantic 𝑛-SuperHyperGraph (or Semantic SuperHyperGraph of level 𝑛) associated
with 𝐺 is the tuple

SNHG (𝑛) := 𝑉𝑛 , 𝐸 𝑛 , 𝐿 𝑛 , ℓ (𝑛) , 𝑤 (𝑛) ,
where
• the level-𝑛 supervertex set is
𝑉𝑛 := P 𝑛 (𝑉);
• the level-𝑛 superedge family is
𝐸 𝑛 :=



P 𝑛−1 (𝑒) \ {∅}

𝑒 ∈ 𝐸𝐻

⊆ P (𝑉𝑛 ) \ {∅};

• the level-𝑛 label set is
𝐿 𝑛 := P (𝐿 𝐻 ) \ {∅};
• the lifted labeling and weight functions ℓ (𝑛) : 𝐸 𝑛 → 𝐿 𝑛 , 𝑤 (𝑛) : 𝐸 𝑛 → [0, 1] are defined by


ℓ (𝑛) P 𝑛−1 (𝑒) \ {∅} := ℓ𝐻 (𝑒),
𝑤 (𝑛) P 𝑛−1 (𝑒) \ {∅} := 𝑤 𝐻 (𝑒)
for all 𝑒 ∈ 𝐸 𝐻 .
Again 𝑉𝑛 ⊆ P 𝑛 (𝑉) and 𝐸 𝑛 ⊆ P (𝑉𝑛 ) \ {∅}, so SNHG (𝑛) is an 𝑛-SuperHyperGraph encoding hierarchical,
multi-scale semantic relations.
Example 6.10.2 (Semantic 2-SuperHyperGraph for a small health–risk ontology). We illustrate a Semantic
2-SuperHyperGraph that organizes health-related concepts and their relations at multiple semantic levels.
Step 1: Semantic graph. Let the concept set be
𝑉 := {Smoking, Obesity, Hypertension, HeartDisease}.
Let the set of relation labels be
𝐿 := {risk factor for, co morbid with}.

We define a directed Semantic Graph
𝐺 = (𝑉, 𝐸, 𝐿, ℓ, 𝑤),
where the edge set 𝐸 ⊆ 𝑉 × 𝑉 consists of
(Smoking, HeartDisease),

(Obesity, HeartDisease),

(Hypertension, HeartDisease),
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Chapter 6. Applications of SuperHyperGraph and the labeling and weight functions are given by ℓ(Smoking, HeartDisease) = ℓ(Obesity, HeartDisease) = ℓ(Hypertension, HeartDisease) = risk factor for, ℓ(Obesity, Hypertension) = co morbid with, 𝑤(Smoking, HeartDisease) = 0.90, 𝑤(Obesity, HeartDisease) = 0.80, 𝑤(Hypertension, HeartDisease) = 0.85, 𝑤(Obesity, Hypertension) = 0.70. Step 2: Semantic hypergraph. From 𝐺 we build a Semantic HyperGraph 𝐻 = (𝑉, 𝐸 𝐻 , 𝐿 𝐻 , ℓ𝐻 , 𝑤 𝐻 ). Consider the hyperedge 𝑒 1 := {Smoking, Obesity, Hypertension, HeartDisease}, representing the joint semantic pattern “cluster of risk factors and outcome”. We set 𝐸 𝐻 := {𝑒 1 }, 𝐿 𝐻 := P (𝐿) \ {∅}, and define ℓ𝐻 (𝑒 1 ) := {risk factor for, co morbid with}, 𝑤 𝐻 (𝑒 1 ) := max{𝑤(𝑒) | 𝑒 ∈ 𝐸, 𝑒 uses only vertices in 𝑒 1 } = 0.90. Thus 𝐻 captures, in one hyperedge, the semantic fact that Smoking, Obesity, and Hypertension jointly relate to HeartDisease as correlated risk factors and comorbid conditions. Step 3: Semantic 2-SuperHyperGraph. We now form the associated Semantic 2-SuperHyperGraph SNHG (2) := (𝑉2 , 𝐸 2 , 𝐿 2 , ℓ (2) , 𝑤 (2) ) as in the definition of Semantic 𝑛-SuperHyperGraph. First, 𝑉2 := P 2 (𝑉) = P (P (𝑉)) is the set of all subsets of P (𝑉). For example, the following are 2-supervertices: 𝑣 1(2) := {Smoking, HeartDisease}, {Obesity, HeartDisease} , 𝑣 2(2) := {Obesity, Hypertension} , 𝑣 3(2) := {Smoking, Obesity, Hypertension, HeartDisease} . Intuitively, 𝑣 1(2) groups “two risk-factor relations to HeartDisease”, 𝑣 2(2) represents a “co-morbidity relation”, and 𝑣 3(2) is the whole hyperedge 𝑒 1 seen as a single nested semantic unit. Next, for 𝑛 = 2 the level-2 superedge family is n 𝐸 2 := P 1 (𝑒) \ {∅} 𝑒 ∈ 𝐸𝐻 o ⊆ P (𝑉2 ) \ {∅}. Since 𝐸 𝐻 = {𝑒 1 } with 𝑒 1 ⊆ 𝑉, we have P 1 (𝑒 1 ) \ {∅} = P (𝑒 1 ) \ {∅}, so a typical 2-superedge is 𝐸 1(2) := {Smoking, HeartDisease}, {Obesity, HeartDisease}, {Hypertension, HeartDisease} , which is an element of 𝑉2 (a subset of P (𝑉)), and thus an element of 𝐸 2 when viewed as a member of P (𝑉2 ). This 2-superedge collects all pairwise risk-factor relations to HeartDisease inside the cluster 𝑒 1 . The label and weight of 𝐸 1(2) are inherited from 𝑒 1 : ℓ (2) (𝐸 1(2) ) := ℓ𝐻 (𝑒 1 ) = {risk factor for, co morbid with}, 𝑤 (2) (𝐸 1(2) ) := 𝑤 𝐻 (𝑒 1 ) = 0.90. Therefore SNHG (2) is a Semantic 2-SuperHyperGraph that encodes not only basic semantic relations between single concepts, but also higher-order patterns of relations (e.g. clusters of risk factors and co-morbidities) as supervertices and superedges at level 2. Such a structure can be used, for instance, in medical decision support or knowledge-based risk analysis, where hierarchical semantic patterns are crucial. 222

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6.11

Behavioral SuperHyperGraphs in Social Sciences

A behavioral graph represents discrete behavioral states as vertices and observed transitions as directed edges,
supporting Markovian or temporal analysis (cf. [1028, 1029]). A behavioral SuperHyperGraph organizes
behavioral states into iterated powerset supervertices and superedges, modeling hierarchical routines, cooccurring behaviors, and multi-level transitions [50].
Definition 6.11.1 (Behavior 𝑛-SuperHyperGraph). [50] Let
𝐺 = (𝑉, 𝐸 𝐺 , 𝑓 , 𝑝)
be a Behavior Graph, where 𝑉 is a finite set of behavioral states, 𝐸 𝐺 ⊆ 𝑉 × 𝑉 is the transition set, 𝑓 : 𝐸 𝐺 → N
is a frequency function, and 𝑝 : 𝐸 𝐺 → [0, 1] is a transition–probability function.
Let
𝐻 = (𝑉, 𝐸 𝐻 , 𝐹, 𝑃)
be the induced Behavior HyperGraph on 𝑉, where 𝐸 𝐻 ⊆ P (𝑉) \ {∅} is the family of hyperedges (co-occurring
state sets), 𝐹 : 𝐸 𝐻 → N is an aggregate frequency, and 𝑃 : 𝐸 𝐻 → [0, 1] is a normalized weight.
For an integer 𝑛 ≥ 1, the Behavior 𝑛-SuperHyperGraph (or Behavior SuperHyperGraph of level 𝑛) associated
with 𝐺 is the tuple

BHG (𝑛) := 𝑉𝑛 , 𝐸 𝑛 , 𝐹 (𝑛) , 𝑃 (𝑛) ,
where
• the level-𝑛 supervertex set is
𝑉𝑛 := P 𝑛 (𝑉),
i.e. the 𝑛-fold iterated powerset of 𝑉;
• the level-𝑛 superedge family is
𝐸 𝑛 :=



P 𝑛−1 (𝑒) \ {∅}

𝑒 ∈ 𝐸𝐻

⊆ P (𝑉𝑛 ) \ {∅};

• the lifted frequency and weight functions 𝐹 (𝑛) : 𝐸 𝑛 → N, 𝑃 (𝑛) : 𝐸 𝑛 → [0, 1] are defined by


𝐹 (𝑛) P 𝑛−1 (𝑒) \ {∅} := 𝐹 (𝑒),
𝑃 (𝑛) P 𝑛−1 (𝑒) \ {∅} := 𝑃(𝑒)
for all 𝑒 ∈ 𝐸 𝐻 .
By construction 𝑉𝑛 ⊆ P 𝑛 (𝑉) and 𝐸 𝑛 ⊆ P (𝑉𝑛 ) \ {∅}, so BHG (𝑛) is an 𝑛-SuperHyperGraph in the usual sense.
Example 6.11.2 (Behavior 2-SuperHyperGraph for smartphone usage patterns). Smartphone usage patterns describe recurring sequences and co-occurrences of smartphone actions (unlocking, app use, notifications) across
time, contexts, and users (cf. [1030, 1031]). We describe a simple real-world Behavioral 2-SuperHyperGraph
that models daily smartphone usage routines of a user.
Step 1: Behavior graph. Let the set of behavioral states be
𝑉 := {Unlock, CheckNews, OpenSNS, WatchVideo, Lock}.
We consider the Behavior Graph
𝐺 = (𝑉, 𝐸 𝐺 , 𝑓 , 𝑝),
where the directed transitions are
𝐸 𝐺 := {(Unlock, CheckNews), (CheckNews, OpenSNS), (OpenSNS, WatchVideo),
(WatchVideo, Lock), (Unlock, OpenSNS), (OpenSNS, Lock)}.
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Chapter 6. Applications of SuperHyperGraph The frequency function 𝑓 : 𝐸 𝐺 → N counts how many times each transition occurs in logged data. For instance, suppose 𝑓 (Unlock, CheckNews) = 60, 𝑓 (CheckNews, OpenSNS) = 50, 𝑓 (WatchVideo, Lock) = 40, 𝑓 (OpenSNS, WatchVideo) = 40, 𝑓 (Unlock, OpenSNS) = 20, 𝑓 (OpenSNS, Lock) = 15. The transition probabilities 𝑝 : 𝐸 𝐺 → [0, 1] are obtained by normalizing frequencies outgoing from each state (e.g. by dividing by the sum of frequencies from that source). Step 2: Behavior hypergraph. From 𝐺 we build the Behavior HyperGraph 𝐻 = (𝑉, 𝐸 𝐻 , 𝐹, 𝑃). Assume empirical logs reveal two frequently co-occurring interaction patterns (“sessions”): 𝑒 1 := {Unlock, CheckNews, OpenSNS, Lock}, 𝑒 2 := {Unlock, OpenSNS, WatchVideo, Lock}. We set 𝐸 𝐻 := {𝑒 1 , 𝑒 2 }. The aggregate frequency 𝐹 : 𝐸 𝐻 → N and normalized weight 𝑃 : 𝐸 𝐻 → [0, 1] summarize how often each session pattern occurs. For example, 𝐹 (𝑒 1 ) = 80, 𝐹 (𝑒 2 ) = 50, 𝑃(𝑒 1 ) = 80 , 80 + 50 𝑃(𝑒 2 ) = 50 . 80 + 50 Step 3: Behavior 2-SuperHyperGraph. We now form the Behavior 2-SuperHyperGraph BHG (2) := 𝑉2 , 𝐸 2 , 𝐹 (2) , 𝑃 (2) as in the definition of Behavior 𝑛-SuperHyperGraph. The level-2 supervertex set is the second iterated powerset 𝑉2 := P 2 (𝑉) = P P (𝑉) , whose elements are sets of subsets of 𝑉. For instance, the following are 2-supervertices: 𝑣 1(2) := {Unlock, CheckNews}, {CheckNews, OpenSNS} , 𝑣 2(2) := {OpenSNS, WatchVideo}, {WatchVideo, Lock} . Intuitively, 𝑣 1(2) encodes the “news-checking” part of a session, while 𝑣 2(2) encodes the “video-watching” part. For 𝑛 = 2, each level-2 superedge is of the form P 1 (𝑒) \ {∅} = P (𝑒) \ {∅} ⊆ P (𝑉), 𝑒 ∈ 𝐸𝐻 . For the pattern 𝑒 1 , the corresponding 2-superedge is 𝐸 1(2) := P (𝑒 1 ) \ {∅} ∈ 𝑉2 , which contains all nonempty subsets of {Unlock, CheckNews, OpenSNS, Lock}. Analogously, 𝐸 2(2) := P (𝑒 2 ) \ {∅} is the second 2-superedge induced by 𝑒 2 . Collecting these, we set 𝐸 2 := {𝐸 1(2) , 𝐸 2(2) } ⊆ P (𝑉2 ) \ {∅}. The lifted frequency and weight functions 𝐹 (2) : 𝐸 2 → N and 𝑃 (2) : 𝐸 2 → [0, 1] are defined by 𝐹 (2) 𝐸 1(2) := 𝐹 (𝑒 1 ) = 80, 𝐹 (2) 𝐸 2(2) := 𝐹 (𝑒 2 ) = 50, 𝑃 (2) 𝐸 1(2) := 𝑃(𝑒 1 ), 𝑃 (2) 𝐸 2(2) := 𝑃(𝑒 2 ). In this way, BHG (2) captures not only single transitions between behavioral states, but also higher-order session patterns and their internal structure as 2-supervertices and 2-superedges. Such a Behavioral 2SuperHyperGraph can be used in social and behavioral sciences to analyze habitual smartphone usage routines, identify clusters of actions, and study how complex behaviors evolve over time. 224

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6.12

SuperHyperGraph Signal Processing

Signal processing studies acquisition, representation, transformation, and analysis of signals to extract information, reduce noise, or enable communication in systems [1032, 1033]. Graph signal processing extends classical signal processing to data on graph vertices, using graph structure for filtering, sampling,
and transforms [1034–1036]. Related concepts in graph signal processing include the Graph Fourier Transform (GFT) [1037–1039], Graph Image Processing [1040], graph filtering (in spectral or vertex-domain
forms) [1041], and the Graph Laplacian [1042, 1043].
Hypergraph signal processing generalizes graph methods to hyperedges connecting many vertices, modeling
multiway interactions and higher-order dependencies in data analysis [96, 97, 1044, 1045]. SuperHyperGraph
signal processing extends hypergraph approaches to iterated powerset supervertices, enabling hierarchical,
multi-level filtering, transforms, and spectral analysis of signals [53].
Definition 6.12.1 (𝑛-SuperHyperGraph Signal Processing). [53] Let 𝑉0 be a finite nonempty base set and let
𝑛 ∈ N0 . Let
SHG (𝑛) = (𝑉, 𝐸)
be an 𝑛-SuperHyperGraph on 𝑉0 , in the sense that
∅ ≠ 𝑉 ⊆ P𝑛 (𝑉0 ),

∅ ≠ 𝐸 ⊆ P ∗ (𝑉) := P (𝑉) \ {∅},

where P 𝑘 (𝑉0 ) denotes the 𝑘-fold iterated powerset of 𝑉0 and P (·) is the usual powerset.
Write 𝑉 = {𝑣 1 , . . . , 𝑣 𝑁𝑛 } and set
𝑀 := max |𝑒|,
𝑒∈𝐸

the maximum cardinality of an 𝑛-superedge.
The adjacency tensor of SHG (𝑛) is the order-𝑀 tensor
𝐴 = ( 𝐴𝑖1 ···𝑖𝑀 )1≤𝑖1 ,...,𝑖𝑀 ≤ 𝑁𝑛 ∈ R 𝑁𝑛 ×···× 𝑁𝑛

(𝑀 factors),

defined as follows. For each superedge
𝑒 ℓ = {𝑣 ℓ1 , . . . , 𝑣 ℓ𝑐 } ∈ 𝐸,

1 ≤ 𝑐 ≤ 𝑀,

we set
−1


∑︁

𝑀!


,
𝑐


𝑘1! · · · 𝑘 𝑐 !



 𝑘1 ,...,𝑘𝑐 ≥1
𝑘1 +···+𝑘𝑐 =𝑀
𝐴𝑖1 ···𝑖𝑀 :=







 0,


if the multiset {𝑣 𝑖1 , . . . , 𝑣 𝑖𝑀 } is obtained from 𝑒 ℓ
by repeating 𝑣 ℓ 𝑗 exactly 𝑘 𝑗 times for 𝑗 = 1, . . . , 𝑐, for some (𝑘 1 , . . . , 𝑘 𝑐 ),
otherwise.

Equivalently, 𝐴𝑖1 ···𝑖𝑀 > 0 precisely when all indices 𝑣 𝑖1 , . . . , 𝑣 𝑖𝑀 belong to the same superedge 𝑒 ℓ ∈ 𝐸, and 0
otherwise.
A (real-valued) signal on SHG (𝑛) is a function 𝑠 : 𝑉 → R, which we identify with the column vector
⊤
𝑠 = 𝑠(𝑣 1 ), . . . , 𝑠(𝑣 𝑁𝑛 ) ∈ R 𝑁𝑛 .
From 𝑠 we form the (𝑀 − 1)-th order signal tensor
𝑆 := 𝑠 ◦ 𝑠 ◦ · · · ◦ 𝑠 ∈ R 𝑁𝑛 ×···× 𝑁𝑛
| {z }

(𝑀 − 1 factors),

𝑀 −1 times

where ◦ denotes the outer product, so that in coordinates
𝑆𝑖1 ···𝑖𝑀 −1 = 𝑠𝑖1 · · · 𝑠𝑖𝑀 −1 .
225

227.

Chapter 6. Applications of SuperHyperGraph The shifted (or filtered) signal tensor 𝑆 ′ is obtained by the mode-𝑀 tensor–vector product 𝑆 ′ := 𝐴 × 𝑀 𝑠, that is, 𝑆𝑖′1 ···𝑖𝑀 −1 := 𝑁𝑛 ∑︁ 1 ≤ 𝑖1 , . . . , 𝑖 𝑀 −1 ≤ 𝑁 𝑛 . 𝐴𝑖1 ···𝑖𝑀 −1 𝑗 𝑠 𝑗 , 𝑗=1 Assume that the adjacency tensor 𝐴 admits an orthogonal CANDECOMP/PARAFAC decomposition 𝐴 = 𝑅 ∑︁ 𝑓𝑟 ∈ R 𝑁 𝑛 , ⟨ 𝑓𝑟 , 𝑓 𝑠 ⟩ = 𝛿 𝑟 𝑠 , 𝜆 𝑟 𝑓𝑟 ◦ · · · ◦ 𝑓𝑟 , | {z } 𝑟=1 𝑀 times where 𝜆𝑟 ∈ R and 𝛿𝑟 𝑠 is the Kronecker delta. Then the rank-one tensors 𝑓𝑟◦( 𝑀 −1) := 𝑓𝑟 ◦ · · · ◦ 𝑓𝑟 , | {z } 𝑟 = 1, . . . , 𝑅, 𝑀 −1 times form an orthonormal basis of the (𝑀 − 1)-th order signal-tensor space (with respect to the Frobenius inner product). The 𝑛-SuperHyperGraph Fourier transform of the signal 𝑠 (equivalently, of 𝑆) is the coefficient vector ⊤ 𝑆b = 𝑆b1 , . . . , 𝑆b𝑅 ∈ R𝑅 , defined by 𝑆b𝑟 := 𝑆, 𝑓𝑟◦( 𝑀 −1) , 𝑟 = 1, . . . , 𝑅, where ⟨·, ·⟩ denotes the Frobenius inner product on (𝑀 − 1)-th order tensors. The data consisting of the adjacency tensor 𝐴, the shift operation 𝑆 ′ = 𝐴 × 𝑀 𝑠, and the Fourier transform 𝑆b is called the 𝑛-SuperHyperGraph Signal Processing structure on SHG (𝑛) . For 𝑛 = 0 this construction reduces to hypergraph signal processing on the underlying hypergraph. Example 6.12.2 (SuperHyperGraph Signal Processing in a smart building). We present a concrete real-world instance of 𝑛-SuperHyperGraph Signal Processing for temperature monitoring in a smart building. Step 1: Building layout as an 𝑛-SuperHyperGraph. Consider a small office floor with four rooms: 𝑉0 := {R1 , R2 , R3 , R4 }. We form a level-1 SuperHyperGraph (i.e. 𝑛 = 1) whose 1-supervertices represent zones (unions of rooms): 𝑉 := { 𝑣 1 , 𝑣 2 , 𝑣 3 } ⊆ P1 (𝑉0 ) = P (𝑉0 ), where 𝑣 1 := {R1 , R2 }, 𝑣 2 := {R2 , R3 }, 𝑣 3 := {R3 , R4 }. Each 𝑣 𝑖 is a 1-supervertex (a subset of rooms) corresponding to a controllable HVAC zone. We define 1-superedges as clusters of zones that share walls, ducts, or strong thermal coupling: 𝑒 1 := {𝑣 1 , 𝑣 2 }, 𝑒 2 := {𝑣 2 , 𝑣 3 }. Thus the superedge family is 𝐸 := {𝑒 1 , 𝑒 2 } ⊆ P ∗ (𝑉) = P (𝑉) \ {∅}. The pair SHG (1) := (𝑉, 𝐸) is a 1-SuperHyperGraph on the base set 𝑉0 . 226

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Chapter 6. Applications of SuperHyperGraph
Step 2: Adjacency tensor of the SuperHyperGraph. We index the 1-supervertices as
𝑉 = {𝑣 1 , 𝑣 2 , 𝑣 3 },

𝑁1 = 3.

The maximum superedge size is
𝑀 := max |𝑒| = 2,
𝑒∈𝐸

so the adjacency tensor 𝐴 has order 𝑀 = 2 and can be viewed as a 3 × 3 matrix
𝐴 = ( 𝐴𝑖 𝑗 )1≤𝑖, 𝑗 ≤3 ∈ R3×3 .
Specializing the general definition to 𝑀 = 2, we set
(
𝛼, if {𝑣 𝑖 , 𝑣 𝑗 } ⊆ 𝑒 ℓ for some 𝑒 ℓ ∈ 𝐸,
𝐴𝑖 𝑗 :=
0, otherwise,
for some fixed positive constant 𝛼 > 0 (for example, 𝛼 = 1).
Because 𝑒 1 = {𝑣 1 , 𝑣 2 } and 𝑒 2 = {𝑣 2 , 𝑣 3 }, the nonzero entries are
𝐴12 = 𝐴21 = 𝛼,

𝐴23 = 𝐴32 = 𝛼,

and all other off-diagonal entries are zero. (Diagonal entries may be chosen as 0 or as self-loop weights,
depending on the modeling choice.)
Step 3: Temperature signal on the SuperHyperGraph. A temperature control system assigns to each zone
𝑣 𝑖 a real-valued temperature (for example, deviation from the desired setpoint in degrees Celsius). This defines
a signal
𝑠 : 𝑉 → R,
𝑠(𝑣 𝑖 ) = temperature deviation in zone 𝑣 𝑖 ,
which we write as a column vector
𝑠(𝑣 1 )
©
ª
𝑠 := 𝑠(𝑣 2 ) ® ∈ R3 .
«𝑠(𝑣 3 ) ¬
Since 𝑀 = 2, the signal tensor reduces to the vector 𝑠 itself; the shifted (or filtered) signal 𝑠′ is obtained by the
mode-2 tensor–vector product, which here is just matrix multiplication:
′

𝑠 := 𝐴𝑠,

𝑠𝑖′ =

3
∑︁

𝐴𝑖 𝑗 𝑠 𝑗 ,

𝑖 = 1, 2, 3.

𝑗=1

Concretely,
𝛼𝑠(𝑣 2 )
©
ª
𝑠′ = 𝛼𝑠(𝑣 1 ) + 𝛼𝑠(𝑣 3 ) ® .
𝛼𝑠(𝑣 2 )
«
¬
′
′
Thus 𝑠 (𝑣 1 ) and 𝑠 (𝑣 3 ) depend on the temperature in the shared neighbor zone 𝑣 2 , while 𝑠′ (𝑣 2 ) averages (up
to the factor 𝛼) the deviations in 𝑣 1 and 𝑣 3 . This operation implements a simple SuperHyperGraph filter that
smooths temperature differences along the zone clusters encoded by the 1-SuperHyperGraph.
Step 4: SuperHyperGraph Fourier analysis. Suppose the adjacency matrix 𝐴 is diagonalizable with an
orthonormal basis of eigenvectors { 𝑓1 , 𝑓2 , 𝑓3 }:
𝐴=

3
∑︁

𝜆𝑟 𝑓𝑟 𝑓𝑟⊤ ,

⟨ 𝑓𝑟 , 𝑓 𝑠 ⟩ = 𝛿 𝑟 𝑠 .

𝑟=1

Then the 1-SuperHyperGraph Fourier transform of 𝑠 is the coefficient vector
b
𝑠1
© ª
𝑠2 ® ,
b
𝑠 := b
b
« 𝑠3 ¬

b
𝑠𝑟 := ⟨𝑠, 𝑓𝑟 ⟩,
227

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Chapter 6. Applications of SuperHyperGraph
which decomposes the temperature signal into “frequency” modes on the SuperHyperGraph. Low-frequency
components correspond to slowly varying temperature deviations across strongly coupled zones, while highfrequency components capture abrupt differences between adjacent zones.
In practice, building engineers can design filters that attenuate high-frequency components (reducing abrupt
temperature jumps) while preserving low-frequency patterns (overall heating/cooling level). This yields
smoother and more energy-efficient control strategies that explicitly exploit the hierarchical zone structure
encoded by the SuperHyperGraph.

6.13

Bond SuperHyperGraph

Bond graphs represent physical systems as elements and junctions connected by bonds carrying power variables,
unifying multi-domain dynamics modeling (cf. [51, 52, 1046, 1047]). Bond SuperHyperGraphs extend bond
graphs using supervertices and superedges over iterated powersets, capturing hierarchical subnetworks and
higher-order multi-port coupling patterns [53].
Definition 6.13.1 (Bond 𝑛-SuperHyperGraph). [53] Let 𝐺 = (𝑉elem ∪¤ 𝑉junc , 𝐸 𝐺 ) be a (finite) bond graph,
where 𝑉elem is the set of element nodes (resistors, capacitors, inductors, sources, etc.), 𝑉junc is the set of junction
nodes, and
𝐸 𝐺 ⊆ 𝑉elem × 𝑉junc
encodes the incidence relation between element nodes and junctions.
The associated Bond HyperGraph is the hypergraph
𝐻 = (𝑉elem , 𝐸 𝐻 ),
where for each junction 𝑗 ∈ 𝑉junc the hyperedge
𝑒 𝑗 := { 𝑢 ∈ 𝑉elem | (𝑢, 𝑗) ∈ 𝐸 𝐺 }
collects exactly the element nodes incident on 𝑗, and
𝐸 𝐻 := { 𝑒 𝑗 ⊆ 𝑉elem | 𝑗 ∈ 𝑉junc }.
Let 𝑉0 := 𝑉elem be the base set of element nodes, and recall the iterated powersets

P 0 (𝑉0 ) := 𝑉0 ,
P 𝑘+1 (𝑉0 ) := P P 𝑘 (𝑉0 ) (𝑘 ≥ 0),
as in Definition 2.2.1. Fix 𝑛 ∈ N.
A Bond 𝑛-SuperHyperGraph on the base bond graph 𝐺 is a pair
BnSHT(𝑛) := (𝑉 (𝑛) , 𝐸 (𝑛) ),
where
• 𝑉 (𝑛) ⊆ P 𝑛 (𝑉0 ) is a nonempty finite set of 𝑛-supervertices. Each 𝑣 ∈ 𝑉 (𝑛) is a nested collection (up to
depth 𝑛) of element nodes and/or Bond HyperGraph hyperedges, representing a junction subnetwork of
𝐺;

• 𝐸 (𝑛) ⊆ P 𝑉 (𝑛) \ {∅} is a nonempty finite family of 𝑛-superedges. Each 𝑒 ∈ 𝐸 (𝑛) is a finite set of
𝑛-supervertices, interpreted as a higher-level “meta-junction” grouping together those subnetworks that
are coupled in the underlying bond graph.
The canonical incidence relation is given by membership: an 𝑛-supervertex 𝑣 ∈ 𝑉 (𝑛) is incident to an 𝑛superedge 𝑒 ∈ 𝐸 (𝑛) precisely when 𝑣 ∈ 𝑒.
When 𝑛 = 1 and we choose

𝑉 (1) = {𝑣} | 𝑣 ∈ 𝑉0 ,


𝐸 (1) = 𝑒 𝑗 | 𝑗 ∈ 𝑉junc ,

the Bond 1-SuperHyperGraph BnSHT(1) coincides with the Bond HyperGraph 𝐻. If, in addition, every
hyperedge 𝑒 𝑗 has cardinality two, then 𝐻 further reduces to the classical bond graph 𝐺. Thus Bond 𝑛SuperHyperGraphs strictly extend Bond HyperGraphs and ordinary bond graphs by encoding hierarchical
junction groupings via iterated powersets.
228

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#p11

230.

Chapter 6. Applications of SuperHyperGraph Example 6.13.2 (Real-world Bond 1-SuperHyperGraph for a DC motor drive). Consider a simple DC motor drive circuit (cf. [1048]) with the following physical components: 𝑉elem := {Se, R, L, M}, where • Se is a DC voltage source, • R is a series resistor (wiring and losses), • L is an inductor (armature inductance), • M is the motor element (electromechanical converter). These element nodes are connected via three junction nodes 𝑉junc := {Js , J1 , J2 }, where: • Js is the source junction (connection between the source and the series resistor), • J1 is the electrical intermediate junction (between resistor and inductor), • J2 is the electromechanical junction (between inductor and motor element). The (directed) incidence relation between element nodes and junctions is encoded by the edge set 𝐸 𝐺 := (Se, Js ), (R, Js ), (R, J1 ), (L, J1 ), (L, J2 ), (M, J2 ) ⊆ 𝑉elem × 𝑉junc . Thus 𝐺 := (𝑉elem ∪¤ 𝑉junc , 𝐸 𝐺 ) is a (finite) bond graph. Step 1: Bond HyperGraph. For each junction 𝑗 ∈ 𝑉junc we form the hyperedge 𝑒 𝑗 := { 𝑢 ∈ 𝑉elem | (𝑢, 𝑗) ∈ 𝐸 𝐺 }, giving 𝑒 Js = {Se, R}, 𝑒 J1 = {R, L}, 𝑒 J2 = {L, M}. The Bond HyperGraph is then 𝐻 := (𝑉elem , 𝐸 𝐻 ), 𝐸 𝐻 := {𝑒 Js , 𝑒 J1 , 𝑒 J2 }. Step 2: Bond 1-SuperHyperGraph. Let the base set be 𝑉0 := 𝑉elem = {Se, R, L, M}, and fix 𝑛 = 1. Recall that P 0 (𝑉0 ) = 𝑉0 , P 1 (𝑉0 ) = P (𝑉0 ), so a 1-supervertex is simply a subset of element nodes. We now group elements into functional subnetworks (modules): 𝑣 sup := {Se, R} (supply and series resistance), 𝑣 line := {R, L} (line and armature inductance), 229

#p300

231.

Chapter 6. Applications of SuperHyperGraph 𝑣 load := {L, M} (inductor and motor load). Each of these is an element of P (𝑉0 ), so we set 𝑉 (1) := {𝑣 sup , 𝑣 line , 𝑣 load } ⊆ P 1 (𝑉0 ). The 1-supervertices represent higher-level subnetworks built from the original element nodes. Next, we describe how these subnetworks are coupled at a meta-level. Define the 1-superedges 𝑒 el(1) := {𝑣 sup , 𝑣 line }, (1) 𝑒 mech := {𝑣 line , 𝑣 load }, and optionally a global coupling (1) 𝑒 sys := {𝑣 sup , 𝑣 line , 𝑣 load }. We then set (1) (1) 𝐸 (1) := 𝑒 el(1) , 𝑒 mech , 𝑒 sys ⊆ P 𝑉 (1) \ {∅}. The pair BnSHT(1) := (𝑉 (1) , 𝐸 (1) ) is a Bond 1-SuperHyperGraph on the base bond graph 𝐺 in the sense of the general definition: 𝑉 (1) ⊆ P 1 (𝑉0 ) is a finite nonempty set of 1-supervertices, and 𝐸 (1) ⊆ P (𝑉 (1) ) \ {∅} is a finite nonempty family of 1-superedges. The Bond SuperHyperGraph BnSHT(1) encodes a two-level view of the DC motor drive: • At the base level 𝑉0 we see individual physical components (source, resistor, inductor, motor) and their junction-based couplings (Bond HyperGraph 𝐻). • At the supervertex level 𝑉 (1) we group these components into functional subnetworks (supply, line, load), while the superedges 𝐸 (1) capture how these subnetworks are interconnected (electrical coupling and electromechanical coupling, plus an optional system-wide superedge). Thus this example shows how a real DC motor drive can be modeled as a Bond SuperHyperGraph, revealing hierarchical structure and modular interactions beyond the ordinary bond graph representation. 6.14 Brain Hypergraphs in Neuroscience Brain graphs represent brain regions as nodes and pairwise connections as edges, modeling structural or functional connectivity patterns between regions [1049–1051]. Brain SuperHyperGraphs use iterated powersets to form supervertices and superedges, encoding hierarchical, overlapping brain modules and higher-order functional interactions explicitly [1052]. Definition 6.14.1 (Brain 𝑛-SuperHyperGraph). [1052] Let 𝑉0 = {𝑟 1 , . . . , 𝑟 𝑁 } be a finite base set of brain regions (Regions of Interest, ROIs). For each integer 𝑘 ≥ 0 define the iterated powersets by P0 (𝑉0 ) := 𝑉0 , P 𝑘+1 (𝑉0 ) := P P 𝑘 (𝑉0 ) , where P(·) denotes the usual powerset. Fix 𝑛 ∈ N0 . A Brain 𝑛-SuperHyperGraph (or Brain SuperHyperGraph of level 𝑛) on 𝑉0 is a pair BSHT (𝑛) = 𝑉 (𝑛) , 𝐸 (𝑛) , where ∅ ≠ 𝑉 (𝑛) ⊆ P𝑛 (𝑉0 ), ∅ ≠ 𝐸 (𝑛) ⊆ P 𝑉 (𝑛) \ {∅}. The elements of 𝑉 (𝑛) are called 𝑛-supervertices and represent nested clusters (modules, subnetworks, or metamodules) of brain regions obtained by applying the powerset operator 𝑛 times to 𝑉0 . The elements of 𝐸 (𝑛) are called 𝑛-superedges and are nonempty sets of 𝑛-supervertices, encoding higher–order, hierarchical interactions between such nested brain modules. 230

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232.

Chapter 6. Applications of SuperHyperGraph The incidence relation is 𝐼 (𝑛) := (𝑣, 𝑒) ∈ 𝑉 (𝑛) × 𝐸 (𝑛) 𝑣∈𝑒 , with canonical projections 𝜋𝑉 : 𝐼 (𝑛) → 𝑉 (𝑛) , (𝑣, 𝑒) ↦→ 𝑣, 𝜋 𝐸 : 𝐼 (𝑛) → 𝐸 (𝑛) , (𝑣, 𝑒) ↦→ 𝑒. When 𝑛 = 0 and 𝑉 (0) = 𝑉0 , the conditions 𝑉 (0) ⊆ P0 (𝑉0 ) = 𝑉0 , 𝐸 (0) ⊆ P (𝑉 (0) ) \ {∅} show that BSHT (0) is exactly a Brain Hypergraph on the vertex set 𝑉0 . For 𝑛 ≥ 1, the construction yields a genuine hierarchical generalization in which both nodes and higher–order connections live on the 𝑛-th iterated powerset of the base set of brain regions. Example 6.14.2 (Brain 2-SuperHyperGraph for large-scale functional networks). Consider a toy fMRI study with four regions of interest (ROIs) 𝑉0 = {𝑟 1 , 𝑟 2 , 𝑟 3 , 𝑟 4 }, where 𝑟 1 is a primary visual area, 𝑟 2 an auditory area, 𝑟 3 a dorsolateral prefrontal cortex region, and 𝑟 4 a hippocampal region. First form the usual powerset P1 (𝑉0 ) = P (𝑉0 ). Among all subsets in P1 (𝑉0 ), suppose empirical connectivity analysis identifies the following task-related functional modules: 𝑀1 := {𝑟 1 , 𝑟 3 } 𝑀2 := {𝑟 2 , 𝑟 3 } 𝑀3 := {𝑟 3 , 𝑟 4 } (visual–prefrontal attention module), (auditory–prefrontal control module), (prefrontal–hippocampal memory module). Each 𝑀𝑖 is an element of P1 (𝑉0 ) and represents a hyperedge-level functional subnetwork at the “first” hierarchical layer. Next, form the second iterated powerset P2 (𝑉0 ) = P P (𝑉0 ) . Inside P2 (𝑉0 ) consider the following two 2-supervertices: 𝑣 𝐴 := {𝑀1 , 𝑀2 } 𝑣 𝐵 := {𝑀3 } ∈ P2 (𝑉0 ) ∈ P2 (𝑉0 ) (task-positive fronto-sensory network), (fronto-hippocampal memory network). Set 𝑉 (2) := {𝑣 𝐴, 𝑣 𝐵 } ⊆ P2 (𝑉0 ). Each element of 𝑉 (2) is a nested collection of ROIs, obtained by applying the powerset operator twice to 𝑉0 , and encodes a large-scale functional network composed of several lower-level modules. During a demanding working-memory task, suppose neuroimaging analysis indicates that these two large-scale networks interact as a unit. This is captured by the 2-superedge 𝑒 1 := {𝑣 𝐴, 𝑣 𝐵 } ⊆ 𝑉 (2) , which represents the higher-order, task-related coupling between the task-positive fronto-sensory network and the memory network. For completeness we may also include a self-network superedge 𝑒 2 := {𝑣 𝐴 }, modeling within-network integration of the task-positive system. 231

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Define

𝐸 (2) := {𝑒 1 , 𝑒 2 } ⊆ P 𝑉 (2) \ {∅}.
Then the pair
BSHT (2) := 𝑉 (2) , 𝐸 (2)



is a Brain 2-SuperHyperGraph in the sense of the preceding definition. The 2-supervertices 𝑣 𝐴 and 𝑣 𝐵 encode
nested functional modules (hierarchical brain networks), while the 2-superedges 𝑒 1 and 𝑒 2 encode higher-order
interactions between these networks during the cognitive task. If we flatten 𝑉 (2) and 𝐸 (2) down to 𝑉0 , we
recover the usual hypergraph representation of functional connectivity between ROIs.

6.15

Legal Citation SuperHyperGraphs

Legal citation is referencing statutes, cases, or regulations within legal writing to support authority, trace
precedent, and justify arguments [1053, 1054]. A Legal Citation Graph represents legal provisions as nodes
and citations as directed edges, modeling pairwise authority, precedent, or dependence [59, 1055]. A Legal
Citation SuperHyperGraph groups provisions into nested supervertices and superedges, capturing higher-order,
multi-document citation patterns and interpretive contexts explicitly [60].
Definition 6.15.1 (Legal Citation 𝑛-SuperHyperGraph). [60] Let 𝑉0 be a finite, nonempty set of legal provisions
(statutes, cases, regulations, guidance, etc.). For 𝑘 ∈ N0 define the iterated powersets by
P 0 (𝑉0 ) := 𝑉0 ,


P 𝑘+1 (𝑉0 ) := P P 𝑘 (𝑉0 ) ,

where P (·) denotes the usual powerset.
Fix an integer 𝑛 ≥ 0 and let 𝐿 be a finite set of citation–type labels (e.g. Authority, Exception, InterpretiveGuidance).
A Legal Citation 𝑛-SuperHyperGraph on the base set 𝑉0 is a triple

LCSHG (𝑛) := 𝑉 (𝑛) , 𝐸 (𝑛) , ℓ (𝑛) ,
where

• 𝑉 (𝑛) ⊆ P 𝑛 (𝑉0 ) is a finite set of 𝑛-supervertices; each 𝑢 ∈ 𝑉 (𝑛) is a (possibly nested) group of provisions
obtained by applying the powerset operator 𝑛 times to 𝑉0 .

• 𝐸 (𝑛) ⊆ 𝑉 (𝑛) × P (𝑉 (𝑛) ) \ {∅} is a finite set of oriented 𝑛-superedges. An element 𝑒 ∈ 𝐸 (𝑛) is a pair
𝑒 = (𝑢, 𝑇),

𝑢 ∈ 𝑉 (𝑛) , ∅ ≠ 𝑇 ⊆ 𝑉 (𝑛) ,

with the intended meaning that the citing supervertex 𝑢 cites every target supervertex 𝑣 ∈ 𝑇. By
convention one may impose 𝑢 ∉ 𝑇 to exclude self–citation (this restriction can be relaxed if desired).
• ℓ (𝑛) : 𝐸 (𝑛) → 𝐿 is a labeling function assigning to each 𝑛-superedge 𝑒 = (𝑢, 𝑇) a citation label
ℓ (𝑛) (𝑒) ∈ 𝐿 describing the semantic type of the citation (for example, whether it is used as an authority,
an exception, or interpretive guidance).

For 𝑛 = 0, if we identify 𝑉 (0) = 𝑉0 and restrict every 0-superedge to pairs of the form (𝑢, {𝑣}), then LCSHG (0)
reduces to a (labeled) Legal Citation Graph. For 𝑛 = 1, if we take 𝑉 (1) ⊆ P (𝑉0 ) and view each 1-superedge
(𝑢, 𝑇) as a citation event in which one provision group 𝑢 cites all provision groups in 𝑇, then LCSHG (1)
recovers a Legal Citation Hypergraph with oriented hyperedges. Thus Legal Citation 𝑛-SuperHyperGraphs
strictly generalize both Legal Citation Graphs and Legal Citation Hypergraphs by allowing nested, higher–order
citation structures.
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Chapter 6. Applications of SuperHyperGraph
Example 6.15.2 (Legal Citation 1-SuperHyperGraph for a data-protection regime). A data-protection regime
is the legal and institutional framework governing collection, use, sharing, and security of personal data,
protecting rights (cf. [1056, 1057]). Consider a simplified legal ecosystem for data protection. Let the base set
𝑉0 consist of specific provisions drawn from real-world sources:
𝑉0 := {𝑎 := “GDPR Article 6(1)”,
𝑏 := “GDPR Recital 47”,
𝑐 := “EU Data Protection Directive 95/46/EC Article 7”,
𝑑 := “National Data Protection Act Section 15”,
𝑒 := “Supreme Court Case X vs. Y (Lawful Interest)”}.
Here 𝑎, 𝑏, 𝑐, 𝑑 are statutory or regulatory provisions and 𝑒 is a judicial decision interpreting “legitimate interest”
as a lawful basis for processing.
Form the powerset
P 1 (𝑉0 ) = P (𝑉0 ),
and define the following provision groups (first-level supervertices):
𝑢 1 := {𝑎, 𝑑}

(domestic implementation of lawful-basis rules),

𝑢 2 := {𝑏, 𝑐}

(EU-level interpretive context for legitimate interest),

𝑢 3 := {𝑒}

(leading case on legitimate-interest balancing test).

Set
𝑉 (1) := {𝑢 1 , 𝑢 2 , 𝑢 3 } ⊆ P 1 (𝑉0 ).
Each 𝑢 𝑖 is a 1-supervertex, i.e. a nonempty subset of 𝑉0 grouping related provisions.
Let the label set of citation types be
𝐿 := {Authority, InterpretiveGuidance, Implementation}.

We now define oriented 1-superedges in the sense of the definition of Legal Citation 𝑛-SuperHyperGraphs.
Intuitively:
• the domestic implementation block 𝑢 1 cites the EU interpretive context 𝑢 2 as Authority;
• the case 𝑢 3 cites both 𝑢 1 and 𝑢 2 as InterpretiveGuidance for its reasoning.
Formally, set
𝐸 (1) := {𝑒 𝐴, 𝑒 𝐼 },
where
𝑒 𝐴 := (𝑢 1 , {𝑢 2 }),

𝑒 𝐼 := (𝑢 3 , {𝑢 1 , 𝑢 2 })

are oriented 1-superedges of the form (𝑢, 𝑇) ∈ 𝑉 (1) × P (𝑉 (1) ) \ {∅} . Define the citation-type labeling function
ℓ (1) : 𝐸 (1) → 𝐿
by
ℓ (1) (𝑒 𝐴) := Authority,

ℓ (1) (𝑒 𝐼 ) := InterpretiveGuidance.

Thus the Legal Citation 1-SuperHyperGraph is

LCSHG (1) := 𝑉 (1) , 𝐸 (1) , ℓ (1) ,
where:
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• each 1-supervertex 𝑢 𝑖 is a group of concrete provisions (statutory sections or a case) from 𝑉0 ;
• the superedge 𝑒 𝐴 encodes that the domestic implementation block 𝑢 1 cites the EU interpretive block 𝑢 2
as authoritative legal basis;
• the superedge 𝑒 𝐼 encodes that the case 𝑢 3 simultaneously cites both 𝑢 1 and 𝑢 2 as interpretive guidance,
capturing a higher-order citation event involving multiple provision groups.
If we “flatten” the supervertices by replacing each 𝑢 𝑖 with its underlying set of atomic provisions, 𝑒 𝐴 and
𝑒 𝐼 reduce to ordinary multi-target citation relations on 𝑉0 , so LCSHG (1) extends a standard legal citation
graph/hypergraph by grouping legal clauses into higher-level supervertices and modeling citation events at that
grouped level.

6.16

River Network SuperHyperGraphs in Geoscientific and Civil Applications

A River Network Graph models river channels as directed edges between confluences and outlets, annotated
with discharge, slope, and length [101]. A River Network SuperHyperGraph organizes channels, tributaries, and
basins into iterated powerset levels, capturing hierarchical catchments, confluences, and multi-scale flow [101].
Definition 6.16.1 (River Network 𝑛-SuperHyperGraph). [101] Let
𝐺 = (𝑉, 𝐸, 𝜑, ℓ)
be a River Network Graph, where 𝑉 is the finite set of river nodes, 𝐸 ⊆ 𝑉 × 𝑉 the set of directed channels,
𝜑 : 𝐸 → R>0 the discharge capacity, and ℓ : 𝐸 → R>0 the channel length.
Let
𝐻 = 𝑉, 𝐸 (1) , 𝜑 𝐻 , ℓ𝐻



be the associated River Network HyperGraph of 𝐺, whose hyperedge set 𝐸 (1) consists of
• binary hyperedges {𝑢, 𝑣} for each directed channel (𝑢, 𝑣) ∈ 𝐸,
• junction hyperedges 𝑈 𝑗 ∪ { 𝑗 } for each confluence node 𝑗 with at least two distinct upstream neighbours
𝑈𝑗,
and where 𝜑 𝐻 , ℓ𝐻 : 𝐸 (1) → R>0 are defined as in the River Network HyperGraph construction (capacities
aggregated, lengths chosen as maximum upstream reach).
Let P 𝑘 (𝑉) denote the 𝑘-fold iterated powerset of 𝑉 as in Definition 2.2.1. Fix 𝑛 ∈ N. We define:
𝑉𝑛 := P 𝑛 (𝑉),
𝐸 𝑛 :=



P 𝑛−1 (𝑒) \ {∅}

𝑒 ∈ 𝐸 (1)

⊆ P 𝑛 (𝑉).

Each element of 𝑉𝑛 is called an 𝑛-supervertex, and each element of 𝐸 𝑛 an 𝑛-superedge. Thus both 𝑉𝑛 and 𝐸 𝑛
are subsets of the same iterated powerset P 𝑛 (𝑉).
The level-𝑛 capacity and length labelings are the maps
𝜑 (𝑛) , ℓ (𝑛) : 𝐸 𝑛 −→ R>0
given on generators by

𝜑 (𝑛) P 𝑛−1 (𝑒) \ {∅} := 𝜑 𝐻 (𝑒),


ℓ (𝑛) P 𝑛−1 (𝑒) \ {∅} := ℓ𝐻 (𝑒)

(𝑒 ∈ 𝐸 (1) ).

The River Network 𝑛-SuperHyperGraph associated with 𝐺 is the quadruple

RNHG (𝑛) := 𝑉𝑛 , 𝐸 𝑛 , 𝜑 (𝑛) , ℓ (𝑛) .
For 𝑛 = 1 one has 𝑉1 = P (𝑉) and 𝐸 1 = {𝑒 | 𝑒 ∈ 𝐸 (1) } ⊆ 𝑉1 , and the labels 𝜑 (1) , ℓ (1) coincide with 𝜑 𝐻 , ℓ𝐻 on
𝐸 (1) . Hence the family RNHG (𝑛) 𝑛≥1 forms a hierarchical River Network SuperHyperGraph built on top of
the River Network HyperGraph.
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Example 6.16.2 (River Network 2-SuperHyperGraph for a mountainous catchment). Consider a small mountainous catchment (cf. [1058]) used in a civil–engineering flood–risk study. The main river has three tributaries
that join upstream of a town protected by levees.
Let the base set of river nodes be
𝑉 := {𝐴, 𝐵, 𝐶, 𝐽1 , 𝐽2 , 𝑂},
where
• 𝐴, 𝐵, 𝐶 are outlet points of three headwater subcatchments (upper tributaries),
• 𝐽1 is the confluence where tributaries 𝐴 and 𝐵 meet,
• 𝐽2 is the downstream confluence where 𝐽1 and tributary 𝐶 meet,
• 𝑂 is the outlet node at the town.
The directed river–channel graph is
𝐺 = (𝑉, 𝐸, 𝜑, ℓ),
with arcs
𝐸 := {( 𝐴, 𝐽1 ), (𝐵, 𝐽1 ), (𝐽1 , 𝐽2 ), (𝐶, 𝐽2 ), (𝐽2 , 𝑂)}.
Here 𝜑 : 𝐸 → R>0 gives bankfull discharge capacity (e.g. in m3 /s) and ℓ : 𝐸 → R>0 gives channel length
(e.g. in km). For instance,
𝜑( 𝐴, 𝐽1 ) = 25,

𝜑(𝐵, 𝐽1 ) = 20,

𝜑(𝐶, 𝐽2 ) = 30,

𝜑(𝐽2 , 𝑂) = 90,

and similarly for ℓ.
The associated River Network HyperGraph
𝐻 = 𝑉, 𝐸 (1) , 𝜑 𝐻 , ℓ𝐻



has hyperedges
𝑒 𝐴,𝐽1 := {𝐴, 𝐽1 },
𝑒𝐶, 𝐽2 := {𝐶, 𝐽2 },
ℎ 𝐽2 := {𝐽1 , 𝐶, 𝐽2 },

𝑒 𝐵,𝐽1 := {𝐵, 𝐽1 },
𝑒 𝐽2 ,𝑂 := {𝐽2 , 𝑂},

𝑒 𝐽1 , 𝐽2 := {𝐽1 , 𝐽2 },
ℎ 𝐽1 := {𝐴, 𝐵, 𝐽1 },

where ℎ 𝐽1 and ℎ 𝐽2 are junction hyperedges representing multi–tributary confluences at 𝐽1 and 𝐽2 . The hyperedge
capacities and lengths 𝜑 𝐻 , ℓ𝐻 are obtained from 𝜑, ℓ (e.g. 𝜑 𝐻 (ℎ 𝐽2 ) is the sum of upstream capacities entering
𝐽2 , and ℓ𝐻 (ℎ 𝐽2 ) is the longest upstream path length into 𝐽2 ).
We now build a River Network 2-SuperHyperGraph. First, the 2-fold iterated powerset of 𝑉 is
𝑉2 := P 2 (𝑉) = P (P (𝑉)).
Each element of 𝑉2 is a nonempty family of vertex subsets and is interpreted as a cluster of river substructures.
For example

𝑈1 := {𝐴, 𝐽1 }, {𝐵, 𝐽1 }, {𝐴, 𝐵, 𝐽1 } ∈ P (P (𝑉)) = 𝑉2 ,

𝑈2 := {𝐽1 , 𝐽2 }, {𝐶, 𝐽2 }, {𝐽1 , 𝐶, 𝐽2 } ∈ 𝑉2 ,
represent, respectively, the local upstream confluence system around 𝐽1 and the downstream confluence system
around 𝐽2 .
According to the general construction, for 𝑛 = 2 the level-2 superedge set is

𝐸 2 := P (𝑒) \ {∅} 𝑒 ∈ 𝐸 (1) ⊆ P 2 (𝑉) = 𝑉2 .
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For instance, for the junction hyperedge ℎ 𝐽2 = {𝐽1 , 𝐶, 𝐽2 } we have

P (ℎ 𝐽2 ) \ {∅} = {𝐽1 }, {𝐶}, {𝐽2 }, {𝐽1 , 𝐶}, {𝐽1 , 𝐽2 }, {𝐶, 𝐽2 }, {𝐽1 , 𝐶, 𝐽2 } ∈ 𝐸 2 ,
which is a 2-superedge whose elements are all nonempty vertex subsets lying inside the local confluence
structure ℎ 𝐽2 .
The lifted capacity and length maps
𝜑 (2) , ℓ (2) : 𝐸 2 → R>0
are defined by

𝜑 (2) P (𝑒) \ {∅} := 𝜑 𝐻 (𝑒),


ℓ (2) P (𝑒) \ {∅} := ℓ𝐻 (𝑒),

𝑒 ∈ 𝐸 (1) .

The River Network 2-SuperHyperGraph
RNHG (2) := 𝑉2 , 𝐸 2 , 𝜑 (2) , ℓ (2)



thus simultaneously encodes:
• individual channels and confluences (via the original hyperedges in 𝐸 (1) ),
• all internal groupings of nodes within each channel or confluence (via 2-superedges such as P (ℎ 𝐽2 ) \{∅}),
• clusters of such groupings (via 2-supervertices such as 𝑈1 and 𝑈2 ).
In practice, hydrologists and civil engineers can use RNHG (2) to design multi–scale flood–mitigation strategies:
for example, they may assign different control policies (retention basins, levee upgrades, temporary diversions)
to distinct 2-supervertices representing upstream, midstream, and downstream confluence systems, while still
keeping track of the detailed channel structure inside each system via the associated 2-superedges.

6.17

Transportation Network SuperHyperGraphs in Geoscientific and Civil Applications

A Transportation Network Graph represents intersections, stations as nodes and edges as links, annotated with
travel time, distance, and capacity. A Transportation Network SuperHyperGraph lifts routes and junctions into
iterated powersets, modeling hierarchical corridors, multimodal hubs, and higher-order flow interactions [101].
Definition 6.17.1 (Transportation Network 𝑛-SuperHyperGraph). [101] Let
𝐺 = (𝑉, 𝐸, 𝜏, ℓ, 𝜅)
be a Transportation Network Graph, where 𝑉 is the finite set of transportation nodes (intersections, stations,
terminals), 𝐸 ⊆ 𝑉 × 𝑉 the set of directed links, and
𝜏, ℓ, 𝜅 : 𝐸 −→ R>0
give, respectively, the typical travel time, physical length, and flow capacity of each directed edge.
Let
𝐻 = 𝑉, 𝐸 (1) , 𝜏𝐻 , ℓ𝐻 , 𝜅 𝐻



be the associated Transportation Network HyperGraph of 𝐺, whose hyperedge set 𝐸 (1) consists of
• binary hyperedges {𝑢, 𝑣} for each directed link (𝑢, 𝑣) ∈ 𝐸,
• outgoing junction hyperedges {𝑖} ∪ { 𝑗 : (𝑖, 𝑗) ∈ 𝐸 } at nodes 𝑖 with at least two outgoing links,
• incoming junction hyperedges {𝑖} ∪ { 𝑗 : ( 𝑗, 𝑖) ∈ 𝐸 } at nodes 𝑖 with at least two incoming links,
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with (𝜏𝐻 , ℓ𝐻 , 𝜅 𝐻 ) defined by aggregating the corresponding edge weights in the usual way (e.g. maximum
travel time and length, summed capacities).
Let P 𝑘 (𝑉) again denote the 𝑘-fold iterated powerset of 𝑉, and fix 𝑛 ∈ N. We define:
𝑉𝑛 := P 𝑛 (𝑉),
𝐸 𝑛 :=



P 𝑛−1 (𝑒) \ {∅}

𝑒 ∈ 𝐸 (1)

⊆ P 𝑛 (𝑉).

Elements of 𝑉𝑛 are called 𝑛-supervertices and elements of 𝐸 𝑛 are 𝑛-superedges.
The level-𝑛 travel-time, length, and capacity labelings are the maps
𝜏 (𝑛) , ℓ (𝑛) , 𝜅 (𝑛) : 𝐸 𝑛 −→ R>0
defined on generators by

𝜏 (𝑛) P 𝑛−1 (𝑒) \ {∅} := 𝜏𝐻 (𝑒),

ℓ (𝑛) P 𝑛−1 (𝑒) \ {∅} := ℓ𝐻 (𝑒),

𝜅 (𝑛) P 𝑛−1 (𝑒) \ {∅} := 𝜅 𝐻 (𝑒)
(𝑒 ∈ 𝐸 (1) ).
The Transportation Network 𝑛-SuperHyperGraph associated with 𝐺 is the quintuple

TNHG (𝑛) := 𝑉𝑛 , 𝐸 𝑛 , 𝜏 (𝑛) , ℓ (𝑛) , 𝜅 (𝑛) .
For 𝑛 = 1 the hyperedge labels (𝜏 (1) , ℓ (1) , 𝜅 (1) ) coincide with (𝜏𝐻 , ℓ𝐻 , 𝜅 𝐻 ) on 𝐸 (1) , so TNHG (1) recovers the
Transportation Network
HyperGraph (up to the canonical identification of vertices with subsets of 𝑉). The

family TNHG (𝑛) 𝑛≥1 is called the Transportation Network SuperHyperGraphs of 𝐺.
Example 6.17.2 (Transportation Network 2-SuperHyperGraph for an urban hub). Consider a small urban
transportation network with one central railway station and three surrounding terminals:
𝑉 := {𝑐, 𝑠, 𝑎, 𝑡},
where 𝑐 = Central Station, 𝑠 = Suburban Station, 𝑎 = Airport, 𝑡 = Bus Terminal.
Directed links connect the central hub 𝑐 to each terminal in both directions:
𝐸 := {(𝑐, 𝑠), (𝑠, 𝑐), (𝑐, 𝑎), (𝑎, 𝑐), (𝑐, 𝑡), (𝑡, 𝑐)}.
For each edge 𝑒 ∈ 𝐸 we specify
𝜏(𝑒) (typical travel time),

ℓ(𝑒) (physical length),

𝜅(𝑒) (flow capacity),

for example
𝜏(𝑐, 𝑠) = 10, 𝜏(𝑐, 𝑎) = 40, 𝜏(𝑐, 𝑡) = 15,
ℓ(𝑐, 𝑠) = 8, ℓ(𝑐, 𝑎) = 30, ℓ(𝑐, 𝑡) = 10,
𝜅(𝑐, 𝑠) = 500, 𝜅(𝑐, 𝑎) = 800, 𝜅(𝑐, 𝑡) = 600,
with similar values assigned to the reverse directions.
From this we build the Transportation Network HyperGraph
𝐻 = 𝑉, 𝐸 (1) , 𝜏𝐻 , ℓ𝐻 , 𝜅 𝐻



as in the definition. The hyperedge set 𝐸 (1) contains:
• binary hyperedges {𝑢, 𝑣} for each (𝑢, 𝑣) ∈ 𝐸, e.g. {𝑐, 𝑠}, {𝑐, 𝑎}, {𝑐, 𝑡};
• an outgoing junction hyperedge
𝑒 out := {𝑐, 𝑠, 𝑎, 𝑡}
at the central hub 𝑐 (three outgoing links);
237

239.

[beta]

Chapter 6. Applications of SuperHyperGraph
• an incoming junction hyperedge
𝑒 in := {𝑐, 𝑠, 𝑎, 𝑡}
at the same hub (three incoming links).
The aggregated labels (𝜏𝐻 , ℓ𝐻 , 𝜅 𝐻 ) can be chosen, for instance, as
𝜏𝐻 (𝑒 out ) := max{𝜏(𝑐, 𝑠), 𝜏(𝑐, 𝑎), 𝜏(𝑐, 𝑡)},

𝜅 𝐻 (𝑒 out ) := 𝜅(𝑐, 𝑠) + 𝜅(𝑐, 𝑎) + 𝜅(𝑐, 𝑡),

with similar conventions for 𝑒 in and the binary hyperedges.
Now let 𝑛 = 2 and consider the 2-fold iterated powerset P 2 (𝑉) = P (P (𝑉)). Define the level-2 supervertex set
and superedge family by
𝑉2 := P 2 (𝑉),


𝐸 2 := P 𝑒 \ {∅} 𝑒 ∈ 𝐸 (1) ⊆ P 2 (𝑉).
Each element 𝑈 ∈ 𝑉2 is a 2-supervertex, i.e. a set of subsets of {𝑐, 𝑠, 𝑎, 𝑡}. For example, the supervertex

𝑈hub := {𝑐, 𝑠, 𝑎, 𝑡}, {𝑐, 𝑠}, {𝑐, 𝑎}, {𝑐, 𝑡} ∈ 𝑉2
represents the central hub together with all direct corridors from 𝑐 to the terminals.
For the outgoing junction hyperedge 𝑒 out = {𝑐, 𝑠, 𝑎, 𝑡}, the associated 2-superedge is

(2)
𝐸 out
:= P 𝑒 out \ {∅} ∈ 𝐸 2 ,
which consists of all nonempty subsets of {𝑐, 𝑠, 𝑎, 𝑡} and thus encodes every possible group of nodes sharing
the central hub. Similarly, each binary hyperedge 𝑒 = {𝑢, 𝑣} yields a 2-superedge


(2)
𝐸 𝑢,𝑣
:= P {𝑢, 𝑣} \ {∅} = {𝑢}, {𝑣}, {𝑢, 𝑣} ,
capturing the local corridor between 𝑢 and 𝑣 with all its sub-combinations.
The level-2 labels
𝜏 (2) , ℓ (2) , 𝜅 (2) : 𝐸 2 → R>0
are defined by

𝜏 (2) P (𝑒) \ {∅} := 𝜏𝐻 (𝑒),


ℓ (2) P (𝑒) \ {∅} := ℓ𝐻 (𝑒),


𝜅 (2) P (𝑒) \ {∅} := 𝜅 𝐻 (𝑒).

The resulting Transportation Network 2-SuperHyperGraph
TNHG (2) := 𝑉2 , 𝐸 2 , 𝜏 (2) , ℓ (2) , 𝜅 (2)



provides a hierarchical model of the urban hub: supervertices encode collections of routes and transfer patterns,
while 2-superedges capture all higher-order groupings of those collections relevant for capacity planning,
multimodal scheduling, and robustness analysis.

6.18

SuperHyperGraph Learning

Graph learning predicts vertex labels or embeddings using edge weights, fitting labeled nodes while enforcing
smoothness across adjacent vertices [1059–1061]. As related concepts, fuzzy graph learning [1062–1064],
digraph learning [1065–1067], and molecular graph learning [1068–1070] are also well known.
Hypergraph learning predicts vertex labels using hyperedge weights, penalizing within-hyperedge disagreement
by pulling each vertex toward its hyperedge mean [1071–1074]. Superhypergraph learning predicts labels on
supervertices via superedge incidences, enforcing within-incidence smoothness over nested vertex sets and
relations.
238

#p300
#p301

240.

[beta]

Chapter 6. Applications of SuperHyperGraph
Definition 6.18.1
 (Weighted graph). A weighted (undirected) graph is a triple 𝐺 = (𝑉, 𝐸, 𝑤) where 𝑉 is a
finite set, 𝐸 ⊆ {𝑢, 𝑣} ⊆ 𝑉 : 𝑢 ≠ 𝑣 , and 𝑤 : 𝐸 → R>0 assigns a positive weight to each edge.
Definition 6.18.2 (Graph learning (Laplacian-regularized transductive learning)). Let 𝐺 = (𝑉, 𝐸, 𝑤) be a
weighted graph, let 𝐿 ⊆ 𝑉 be a labeled vertex set, let 𝑌 be a label space, and let ℓ : R𝑐 × 𝑌 → R ≥0 be a loss.
A graph learning problem is to find a prediction function 𝑓 : 𝑉 → R𝑐 minimizing
∑︁
∑︁

ℓ 𝑓 (𝑣), 𝑦 𝑣 + 𝜆
min 𝑐
𝑤({𝑢, 𝑣}) ∥ 𝑓 (𝑢) − 𝑓 (𝑣) ∥ 22 , 𝜆 > 0.
𝑓 :𝑉→R

𝑣∈𝐿

{𝑢,𝑣 } ∈𝐸

Example
6.18.3 (Graph learning: toy semi-supervised node classification). Let 𝑉 = {1, 2, 3, 4} and 𝐸 =

{1, 2}, {2, 3}, {3, 4} with weights 𝑤({1, 2}) = 𝑤({2, 3}) = 𝑤({3, 4}) = 1. Let the labeled set be 𝐿 = {1, 4}
with binary labels 𝑦 1 = 0 and 𝑦 4 = 1. Graph learning seeks 𝑓 : 𝑉 → R minimizing
∑︁


2
ℓ 𝑓 (1), 0 + ℓ 𝑓 (4), 1 + 𝜆
𝑓 (𝑢) − 𝑓 (𝑣) ,
{𝑢,𝑣 } ∈𝐸

so 𝑓 (2), 𝑓 (3) are encouraged to interpolate smoothly between the labeled endpoints.
Definition 6.18.4 (Weighted hypergraph). A weighted hypergraph is a triple 𝐻 = (𝑉, E, 𝑤) where 𝑉 is a finite
set of vertices, E ⊆ P (𝑉) \ {∅} is a finite family of hyperedges, and 𝑤 : E → R>0 assigns a positive weight to
each hyperedge.
Definition 6.18.5 (Hypergraph learning (incidence-regularized learning)). Let 𝐻 = (𝑉, E, 𝑤) be a weighted
hypergraph. For 𝑒 ∈ E define the (hyperedge) mean
1 ∑︁
𝑓 (𝑣) ∈ R𝑐 .
𝑓¯𝑒 :=
|𝑒| 𝑣 ∈𝑒
A hypergraph learning problem (semi-supervised transductive) is to find 𝑓 : 𝑉 → R𝑐 minimizing
∑︁
∑︁
∑︁

𝑤(𝑒)
∥ 𝑓 (𝑣) − 𝑓¯𝑒 ∥ 22 , 𝜆 > 0.
min 𝑐
ℓ 𝑓 (𝑣), 𝑦 𝑣 + 𝜆
𝑓 :𝑉→R

𝑣∈𝐿

𝑣 ∈𝑒

𝑒∈ E

This regularizer penalizes label/representation variation inside each hyperedge.
Example 6.18.6 (Hypergraph learning: group-consistency on overlapping teams). Let 𝑉 = {𝑎, 𝑏, 𝑐, 𝑑} and
hyperedges
E = {𝑒 1 , 𝑒 2 },
𝑒 1 = {𝑎, 𝑏, 𝑐}, 𝑒 2 = {𝑏, 𝑐, 𝑑},
with 𝑤(𝑒 1 ) = 𝑤(𝑒 2 ) = 1. Let 𝐿 = {𝑎, 𝑑} with labels 𝑦 𝑎 = 0 and 𝑦 𝑑 = 1. Hypergraph learning seeks 𝑓 : 𝑉 → R
minimizing
∑︁ ∑︁


2
ℓ 𝑓 (𝑎), 0 + ℓ 𝑓 (𝑑), 1 + 𝜆
𝑓 (𝑣) − 𝑓¯𝑒 2 ,
𝑒∈ E 𝑣 ∈𝑒

where 𝑓¯𝑒1 = 31 ( 𝑓 (𝑎) + 𝑓 (𝑏) + 𝑓 (𝑐)) and 𝑓¯𝑒2 = 13 ( 𝑓 (𝑏) + 𝑓 (𝑐) + 𝑓 (𝑑)).

Thus (𝑏, 𝑐) are influenced by both

groups, enforcing consistent predictions inside each hyperedge.
Definition 6.18.7 (Weighted 𝑛-superhypergraph). A weighted 𝑛-superhypergraph is a quadruple (𝑉, 𝐸, 𝜕, 𝑤)
where (𝑉, 𝐸, 𝜕) is an 𝑛-SuperHyperGraph and 𝑤 : 𝐸 → R>0 assigns a positive weight to each edge-identifier.
Definition 6.18.8 (𝑛-SuperHyperGraph learning). Let (𝑉, 𝐸, 𝜕, 𝑤) be a weighted 𝑛-superhypergraph. For each
𝑒 ∈ 𝐸 and each 𝑓 : 𝑉 → R𝑐 , define the incidence-mean
𝑓¯𝜕(𝑒) :=

∑︁
1
𝑓 (𝑈) ∈ R𝑐 .
|𝜕 (𝑒)|
𝑈 ∈𝜕(𝑒)

An 𝑛-SuperHyperGraph learning problem is to find 𝑓 : 𝑉 → R𝑐 minimizing
∑︁
∑︁
∑︁

min 𝑐
ℓ 𝑓 (𝑈), 𝑦𝑈 + 𝜆
𝑤(𝑒)
∥ 𝑓 (𝑈) − 𝑓¯𝜕(𝑒) ∥ 22 ,
𝑓 :𝑉→R

𝑈∈𝐿

𝜆 > 0,

𝑈 ∈𝜕(𝑒)

𝑒∈𝐸

where 𝐿 ⊆ 𝑉 is a labeled set of 𝑛-supervertices. When 𝑛 ≥ 1, this is also called superhypergraph learning.
239

241.

[beta]

Chapter 6. Applications of SuperHyperGraph
Example 6.18.9 (SuperHypergraph learning: learning on nested supervertices (𝑛 = 2)). Let 𝑉0 = {𝑥, 𝑦, 𝑧} and
define 2-supervertices
𝑈1 = {{𝑥}},

𝑈2 = {{𝑦}},

𝑈3 = {{𝑥}, {𝑦}},

𝑈4 = {{𝑧}}.

Set 𝑉 = {𝑈1 , 𝑈2 , 𝑈3 , 𝑈4 } and let 𝐸 = {𝑠1 , 𝑠2 } with incidence map
𝜕 (𝑠1 ) = {𝑈1 , 𝑈3 },

𝜕 (𝑠2 ) = {𝑈2 , 𝑈3 , 𝑈4 },

and weights 𝑤(𝑠1 ) = 𝑤(𝑠2 ) = 1. Let the labeled set be 𝐿 = {𝑈1 , 𝑈4 } with 𝑦𝑈1 = 0 and 𝑦𝑈4 = 1. Superhypergraph learning seeks 𝑓 : 𝑉 → R minimizing
∑︁ ∑︁


2
𝑓 (𝑈) − 𝑓¯𝜕(𝑒) 2 ,
ℓ 𝑓 (𝑈1 ), 0 + ℓ 𝑓 (𝑈4 ), 1 + 𝜆
𝑒∈𝐸 𝑈 ∈𝜕(𝑒)



where 𝑓¯𝜕(𝑠1 ) = 21 𝑓 (𝑈1 ) + 𝑓 (𝑈3 ) and 𝑓¯𝜕(𝑠2 ) = 13 𝑓 (𝑈2 ) + 𝑓 (𝑈3 ) + 𝑓 (𝑈4 ) . Hence 𝑈3 (a nested set-of-sets)
couples both incidences and mediates information between labeled supervertices.
Theorem 6.18.10 (𝑛-SuperHyperGraph learning generalizes hypergraph learning). Fix 𝑛 ∈ N0 . For every
weighted hypergraph 𝐻 = (𝑉0 , E, 𝑤) and every hypergraph learning instance as in Definition 6.18.5, there
exists a weighted 𝑛-superhypergraph (𝑉 (𝑛) , 𝐸 (𝑛) , 𝜕 (𝑛) , 𝑤 (𝑛) ) and an 𝑛-superhypergraph learning instance as
in Definition 6.18.8 such that:
1. the vertex sets are in bijection and labels/loss terms correspond exactly; and
2. the regularization terms are equal under this bijection; hence minimizers correspond.
Therefore, 𝑛-SuperHyperGraph learning is a strict extension of hypergraph learning (at least in the sense of
containing it as a special case).
Proof. Define the nested-singleton injection 𝜄𝑛 : 𝑉0 → P 𝑛 (𝑉0 ) by
𝜄0 (𝑣) := 𝑣,

𝜄 𝑘+1 (𝑣) := {𝜄 𝑘 (𝑣)}

(𝑘 ≥ 0).

Let
𝑉 (𝑛) := 𝜄𝑛 (𝑉0 ) ⊆ P 𝑛 (𝑉0 ).
Let the edge-identifier set be 𝐸 (𝑛) := E (reuse each hyperedge as an identifier), define weights 𝑤 (𝑛) (𝑒) := 𝑤(𝑒)
for 𝑒 ∈ E, and define incidence by
𝜕 (𝑛) (𝑒) := {𝜄𝑛 (𝑣) : 𝑣 ∈ 𝑒} ⊆ 𝑉 (𝑛)

(𝑒 ∈ E).

Then (𝑉 (𝑛) , 𝐸 (𝑛) , 𝜕 (𝑛) ) is an 𝑛-SuperHyperGraph over 𝑉0 , hence (𝑉 (𝑛) , 𝐸 (𝑛) , 𝜕 (𝑛) , 𝑤 (𝑛) ) is a weighted 𝑛superhypergraph.
Now transfer any prediction function 𝑓0 : 𝑉0 → R𝑐 to 𝑓𝑛 : 𝑉 (𝑛) → R𝑐 by
𝑓𝑛 (𝜄𝑛 (𝑣)) := 𝑓0 (𝑣)

(𝑣 ∈ 𝑉0 ).

This correspondence is bijective because 𝜄𝑛 is injective and 𝑉 (𝑛) = 𝜄𝑛 (𝑉0 ).
Fix 𝑒 ∈ E. The incidence set 𝜕 (𝑛) (𝑒) is in bijection with 𝑒 via 𝑣 ↦→ 𝜄𝑛 (𝑣), hence
𝑓¯𝜕 (𝑛) (𝑒) =
Therefore,

∑︁
𝑈 ∈𝜕 (𝑛) (𝑒)

1
|𝜕 (𝑛) (𝑒)|

∑︁

𝑓𝑛 (𝑈) =

1 ∑︁
1 ∑︁
𝑓𝑛 (𝜄𝑛 (𝑣)) =
𝑓0 (𝑣) = 𝑓¯𝑒 .
|𝑒| 𝑣 ∈𝑒
|𝑒| 𝑣 ∈𝑒

∑︁

∑︁

𝑈 ∈𝜕 (𝑛) (𝑒)

∥ 𝑓𝑛 (𝑈) − 𝑓¯𝜕 (𝑛) (𝑒) ∥ 22 =

∥ 𝑓𝑛 (𝜄𝑛 (𝑣)) − 𝑓¯𝑒 ∥ 22 =

𝑣 ∈𝑒

𝑣 ∈𝑒

240

∥ 𝑓0 (𝑣) − 𝑓¯𝑒 ∥ 22 .

#p240

242.

Chapter 6. Applications of SuperHyperGraph Multiplying by the weights 𝑤 (𝑛) (𝑒) = 𝑤(𝑒) and summing over 𝑒 ∈ E yields equality of the full regularizers: ∑︁ ∑︁ ∑︁ ∑︁ 𝑤 (𝑛) (𝑒) ∥ 𝑓𝑛 (𝑈) − 𝑓¯𝜕 (𝑛) (𝑒) ∥ 22 = 𝑤(𝑒) ∥ 𝑓0 (𝑣) − 𝑓¯𝑒 ∥ 22 . 𝑒∈𝐸 (𝑛) 𝑒∈ E 𝑈 ∈𝜕 (𝑛) (𝑒) 𝑣 ∈𝑒 Finally, if the labeled set in the hypergraph instance is 𝐿 0 ⊆ 𝑉0 , define 𝐿 𝑛 := 𝜄𝑛 (𝐿 0 ) ⊆ 𝑉 (𝑛) and set 𝑦 𝜄𝑛 (𝑣) := 𝑦 𝑣 . Then ∑︁ ∑︁ ℓ 𝑓𝑛 (𝑈), 𝑦𝑈 = ℓ 𝑓0 (𝑣), 𝑦 𝑣 , 𝑈 ∈ 𝐿𝑛 𝑣 ∈ 𝐿0 so the full objectives coincide under 𝑓𝑛 (𝜄𝑛 (𝑣)) = 𝑓0 (𝑣). Hence minimizers correspond bijectively, and hypergraph learning is realized as a special case of 𝑛-superhypergraph learning. □ 6.19 SuperHyperGraph Attention Networks Graph Attention Networks (GATs) learn node embeddings on graphs by attention-weighted neighbor aggregation, emphasizing important adjacent nodes per layer. As related concepts, Fuzzy Graph Attention Networks [1075, 1076] and Directed Graph Attention Networks [1077, 1078] are also well known. HyperGraph Attention Networks (HGATs) extend GATs to hypergraphs, attentively aggregating messages between vertices and hyperedges via incidence relations [1079–1082]. SuperHyperGraph Attention Networks (SuHGATs) generalize HGATs to 𝑛-superhypergraphs, applying attention-based message passing between supervertices and superedges [1083]. Definition 6.19.1 (HyperGraph Attention Network (HGAT)). [1079–1082] Let 𝐺 = (𝑉, 𝐸, 𝜔) be a (weighted) hypergraph with |𝑉 | = 𝑁 vertices and |𝐸 | = 𝑀 hyperedges. Let 𝐴 ∈ {0, 1} 𝑁 × 𝑀 be the incidence matrix, where 𝐴𝑖 𝑗 = 1 ⇐⇒ 𝑣 𝑖 ∈ 𝑒 𝑗 . At layer ℓ, let 𝐻 (ℓ ) ∈ R 𝑁 ×𝑑 be the vertex-feature matrix and 𝐸 (ℓ ) ∈ R 𝑀 ×𝑑 the hyperedge-feature matrix. A single HGAT layer is the composition of two attentive aggregations: ′ (1) Vertex → Hyperedge attention. Choose a learnable projection 𝑊 ∈ R𝑑×𝑑 and an attention kernel 𝑎 : ′ ′ R𝑑 × R𝑑 → R. For each incident pair (𝑖, 𝑗) with 𝐴𝑖 𝑗 = 1, compute a raw score ) 𝑠𝑖(ℓ𝑗 ) = 𝑎 ℎ𝑖(ℓ ) 𝑊, 𝑒 (ℓ 𝑗 𝑊 , then row-normalize over hyperedges incident to 𝑖 (masking non-incidences) to obtain attention weights: 𝛼𝑖(ℓ𝑗 ) = exp(𝑠𝑖(ℓ𝑗 ) ) Í exp(𝑠𝑖(ℓ𝑗 ′) ) and 𝛼𝑖(ℓ𝑗 ) = 0 if 𝐴𝑖 𝑗 = 0. 𝑗 ′ : 𝐴𝑖 𝑗 ′ =1 Equivalently, in masked matrix form one may write A (ℓ ) = 𝐴 ⊙ softmax LeakyReLU 𝐻 (ℓ ) 𝑊 (𝐸 (ℓ ) 𝑊) T ∈ [0, 1] 𝑁 ×𝑀 . Update hyperedge features by attentive aggregation: 𝐸 (ℓ+1) = 𝜎 (A (ℓ ) ) T 𝐻 (ℓ ) . ′ (2) Hyperedge → Vertex attention. Choose another projection 𝑊1 ∈ R𝑑×𝑑 and define B (ℓ ) = 𝐴T ⊙ softmax LeakyReLU 𝐸 (ℓ ) 𝑊1 (𝐻 (ℓ ) 𝑊1 ) T ∈ [0, 1] 𝑀 × 𝑁 . Update vertex features by 𝐻 (ℓ+1) = 𝜎 (B (ℓ ) ) T 𝐸 (ℓ ) . Stacking 𝐿 such layers yields final vertex embeddings 𝐻 (𝐿) (and optionally hyperedge embeddings 𝐸 (𝐿) ). Multi-head variants replace (𝑊, 𝑎) by (𝑊 (𝑘 ) , 𝑎 (𝑘 ) ) and concatenate/average head outputs. 241

#p301

243.

[beta]

Chapter 6. Applications of SuperHyperGraph
Example 6.19.2 (A concrete HGAT example on a tiny hypergraph). Consider the hypergraph 𝐺 = (𝑉, 𝐸) with
𝑉 = {𝑣 1 , 𝑣 2 , 𝑣 3 },

𝐸 = {𝑒 1 , 𝑒 2 },

𝑒 1 = {𝑣 1 , 𝑣 2 }, 𝑒 2 = {𝑣 2 , 𝑣 3 }.

Its incidence matrix 𝐴 ∈ {0, 1}3×2 (rows 𝑣 𝑖 , columns 𝑒 𝑗 ) is
1
©
𝐴 = 1
«0

0
ª
1® .
1¬

Take one-dimensional features (𝑑 = 1):
1
© ª
𝐻 (0) = 2®
«3¬

𝐸 (0) =

(vertex features),



0.5
1.5


(hyperedge features).

Choose 𝑊 = 1 and an attention kernel 𝑎(𝑥, 𝑦) = 𝑥𝑦 (dot-product in 𝑑 = 1), and take 𝜎 as the identity.
Vertex→Hyperedge attention. For each incidence (𝑖, 𝑗) with 𝐴𝑖 𝑗 = 1, the raw score is 𝑠𝑖 𝑗 = ℎ𝑖(0) 𝑒 (0)
𝑗 :
𝑠11 = 1 · 0.5 = 0.5,

𝑠21 = 2 · 0.5 = 1,

𝑠22 = 2 · 1.5 = 3,

𝑠32 = 3 · 1.5 = 4.5.

Row-normalize by softmax over hyperedges incident to each vertex:
𝛼11 = 1, 𝛼12 = 0,
𝛼22 =

𝛼21 =

𝑒1
2.7182818
=
= 0.1192029,
𝑒 1 + 𝑒 3 2.7182818 + 20.0855369

𝑒3
20.0855369
= 0.8807971,
=
1
3
2.7182818 + 20.0855369
𝑒 +𝑒

𝛼31 = 0, 𝛼32 = 1.

Hence
1
©
0.1192029
𝛼=
0
«

0
ª
0.8807971® .
1
¬

Update hyperedge features by 𝐸 (1) = 𝛼T 𝐻 (0) :
𝐸 1(1) = 1 · 1 + 0.1192029 · 2 + 0 · 3 = 1 + 0.2384058 = 1.2384058,
𝐸 2(1) = 0 · 1 + 0.8807971 · 2 + 1 · 3 = 1.7615942 + 3 = 4.7615942,
so
𝐸

(1)




1.2384058
=
.
4.7615942

(0)
Hyperedge→Vertex attention (using 𝐸 (1) ). For each incidence ( 𝑗, 𝑖) with 𝐴𝑖 𝑗 = 1, set 𝑡 𝑗𝑖 = 𝐸 (1)
and
𝑗 ℎ𝑖
softmax over vertices in each hyperedge. For 𝑒 1 (incident to 𝑣 1 , 𝑣 2 ):

𝑡1,1 = 1.2384058 · 1 = 1.2384058,

𝑡1,2 = 1.2384058 · 2 = 2.4768116,

𝑒 1.2384058
3.4500998
=
= 0.2242645,
1.2384058
2.4768116
3.4500998 + 11.9032595
𝑒
+𝑒
For 𝑒 2 (incident to 𝑣 2 , 𝑣 3 ):
𝛽1,1 =

𝑡 2,2 = 4.7615942 · 2 = 9.5231884,

𝛽1,2 = 0.7757355.

𝑡2,3 = 4.7615942 · 3 = 14.2847826,

𝑒 9.5231884
= 0.008479449, 𝛽2,3 = 0.991520551.
𝑒 9.5231884 + 𝑒 14.2847826
Thus (rows 𝑒 1 , 𝑒 2 ; columns 𝑣 1 , 𝑣 2 , 𝑣 3 )


0.2242645
0.7757355
0
𝛽=
.
0
0.008479449 0.991520551
𝛽2,2 =

242

244.

Chapter 6. Applications of SuperHyperGraph Update vertex features by 𝐻 (1) = 𝛽T 𝐸 (1) : ℎ1(1) = 0.2242645 · 1.2384058 = 0.277730456, ℎ2(1) = 0.7757355 · 1.2384058 + 0.008479449 · 4.7615942 = 0.9606891 + 0.0403619 = 1.0010510, ℎ3(1) = 0.991520551 · 4.7615942 = 4.7212185, so 0.277730456 © ª 𝐻 (1) = 1.001051040® . «4.721218505¬ This is a fully specified, numerical HGAT layer computation on a concrete hypergraph. Definition 6.19.3 (𝑛-SuperHyperGraph Attention Network (n-SuHGAT)). [1083] Fix a finite base set 𝑉0 and an integer 𝑛 ≥ 1. Let P 𝑛 (𝑉0 ) denote the 𝑛-th iterated powerset. An 𝑛-SuperHyperGraph is a pair SuHG(𝑛) = (𝑉 (𝑛) , 𝐸 (𝑛) ), 𝑉 (𝑛) , 𝐸 (𝑛) ⊆ P 𝑛 (𝑉0 ), whose elements are called 𝑛-supervertices and 𝑛-superedges, respectively. Let 𝑁 = |𝑉 (𝑛) |, 𝑀 = |𝐸 (𝑛) |, and let the incidence matrix be 𝐴 (𝑛) ∈ {0, 1} 𝑁 × 𝑀 , (𝑛) 𝐴𝑢𝑣 = 1 ⇐⇒ 𝑛-supervertex 𝑢 is incident to 𝑛-superedge 𝑣. At layer ℓ, let 𝐻 (ℓ ) ∈ R 𝑁 ×𝑑 be the 𝑛-supervertex features and 𝐸 (ℓ ) ∈ R 𝑀 ×𝑑 the 𝑛-superedge features. A single n-SuHGAT layer is defined by the same two-phase attentive message passing, but using 𝐴 (𝑛) : ′ (1) Supervertex → Superedge attention. With 𝑊 ∈ R𝑑×𝑑 , A (ℓ,𝑛) = 𝐴 (𝑛) ⊙ softmax LeakyReLU 𝐻 (ℓ ) 𝑊 (𝐸 (ℓ ) 𝑊) T ∈ [0, 1] 𝑁 × 𝑀 , 𝐸 (ℓ+1) = 𝜎 (A (ℓ,𝑛) ) T 𝐻 (ℓ ) . ′ (2) Superedge → Supervertex attention. With 𝑊1 ∈ R𝑑×𝑑 , B (ℓ,𝑛) = ( 𝐴 (𝑛) ) T ⊙ softmax LeakyReLU 𝐸 (ℓ ) 𝑊1 (𝐻 (ℓ ) 𝑊1 ) T ∈ [0, 1] 𝑀 × 𝑁 , 𝐻 (ℓ+1) = 𝜎 (B (ℓ,𝑛) ) T 𝐸 (ℓ ) . Stacking 𝐿 layers defines the n-SuHGAT and yields embeddings 𝐻 (𝐿) on 𝑛-supervertices (and optionally 𝐸 (𝐿) on 𝑛-superedges). Again, multi-head variants are obtained by running multiple attention heads in parallel and concatenating/averaging. Example 6.19.4 (A concrete SuperHyperGraph Attention example (level 𝑛 = 2) on nested supervertices). Let the base set be 𝑉0 = {𝑎, 𝑏, 𝑐} and take 𝑛 = 2. Define three 2-supervertices (elements of P 2 (𝑉0 ) = P (P (𝑉0 ))) by 𝑢 1 = {{𝑎}}, 𝑢 2 = {{𝑏}}, 𝑢 3 = {{𝑎}, {𝑏}}. Let 𝑉 (2) = {𝑢 1 , 𝑢 2 , 𝑢 3 } and let 𝐸 (2) = {𝑠1 , 𝑠2 } with incidence map 𝜕 (𝑠1 ) = {𝑢 1 , 𝑢 3 }, 𝜕 (𝑠2 ) = {𝑢 2 , 𝑢 3 }. Equivalently, the incidence matrix 𝐴 (2) ∈ {0, 1}3×2 (rows 𝑢 𝑖 , columns 𝑠 𝑗 ) is 1 © 𝐴 (2) = 1 «0 0 ª 1® , 1¬ which has the same pattern as the previous hypergraph example, but now the “vertices” are nested objects. 243

#p301

245.

Chapter 6. Applications of SuperHyperGraph Assign one-dimensional initial features to supervertices and superedges: 1 © ª 𝐻 (0) = 2® «3¬ 𝐸 (0) = (2-supervertex features for 𝑢 1 , 𝑢 2 , 𝑢 3 ), 0.5 1.5 (2-superedge features for 𝑠1 , 𝑠2 ). Using exactly the same two-phase attentive message passing (with 𝐴 (2) in place of 𝐴), and the same choices 𝑊 = 1, 𝑎(𝑥, 𝑦) = 𝑥𝑦, and 𝜎 = id, we obtain the same numerical attentions 1 © 𝛼 = 0.1192029 0 « 0 ª 0.8807971® , 1 ¬ 𝐸 (1) T =𝛼 𝐻 (0) 1.2384058 = , 4.7615942 0.277730456 © ª 𝐻 (1) = 𝛽T 𝐸 (1) = 1.001051040® . «4.721218505¬ Interpretation: 𝑢 3 = {{𝑎}, {𝑏}} is a “higher” supervertex sharing incidence with both superedges, so its updated embedding becomes large after the second attention phase, reflecting strong multi-incidence influence. 𝛽= 0.2242645 0.7757355 0 0.008479449 0 , 0.991520551 244

246.

Chapter 7 Extensional Definitions: (𝑚, 𝑛)-SuperHyperGraph In this chapter, we define the notion of an (𝑚, 𝑛)-SuperHyperGraph as an extension of the 𝑛-SuperHyperGraph and examine its fundamental properties. 7.1 (𝑚, 𝑛)-SuperHyperGraph A (𝑚, 𝑛)-SuperHyperGraph is a mathematical structure in which each vertex corresponds to an (𝑚, 𝑛)superhyperfunction defined on a base set, while the hyperedges group such functions together to represent higher-order relationships and contextual connections. An (ℎ, 𝑘)-ary (𝑚, 𝑛)-SuperHyperGraph further generalizes this idea by taking vertices as (ℎ, 𝑘)-ary (𝑚, 𝑛)-superhyperfunctions [1084]. Notation 7.1.1. For a nonempty base set 𝑆 define P0 (𝑆) := 𝑆, P𝑚+1 (𝑆) := P P𝑚 (𝑆) (𝑚 ∈ N0 ), so P1 (𝑆) = P (𝑆), P2 (𝑆) = P (P (𝑆)), etc. We also use the Cartesian power 𝑋 ℎ := 𝑋 × · · · × 𝑋 for ℎ ∈ N. | {z } ℎ copies Definition 7.1.2 ((𝑚, 𝑛)-superhyperfunction). [115,1085] Let 𝑚, 𝑛 ∈ N and 𝑆 ≠ ∅. An (𝑚, 𝑛)-superhyperfunction on 𝑆 is a map 𝑓 : P𝑚 (𝑆) −→ P𝑛 (𝑆). Equivalently, 𝑓 ∈ Hom P𝑚 (𝑆), P𝑛 (𝑆) as functions of sets. Definition 7.1.3 ((𝑚, 𝑛)-SuperHyperGraph). [1084] Fix 𝑚, 𝑛 ∈ N and a nonempty base set 𝑆. Let n o 𝔉𝑚,𝑛 (𝑆) := 𝑓 : P𝑚 (𝑆) → P𝑛 (𝑆) . An (𝑚, 𝑛)-SuperHyperGraph is a pair SHG (𝑚,𝑛) := (𝑉, E), where 𝑉 ⊆ 𝔉𝑚,𝑛 (𝑆) is a nonempty set of vertices (each vertex is a concrete (𝑚, 𝑛)-superhyperfunction) and ∅ ≠ E ⊆ P (𝑉) \ {∅} is a nonempty family of nonempty hyperedges. Each hyperedge 𝐸 ∈ E groups a finite, nonempty set of superhyperfunctions to encode higher-order relations/constraints among them. For reference, a comparison between an 𝑛-SuperHyperGraph and an (𝑚, 𝑛)-SuperHyperGraph is summarized in Table 7.1. Definition 7.1.4 ((ℎ, 𝑘)-ary (𝑚, 𝑛)-superhyperfunction). [115] Let ℎ, 𝑘 ∈ N and 𝑚, 𝑛 ∈ N. An (ℎ, 𝑘)-ary (𝑚, 𝑛)-superhyperfunction on 𝑆 is a map ℎ 𝑘 𝐹 : P𝑚 (𝑆) −→ P𝑛 (𝑆) . Writing 𝐹 ( 𝐴1 , . . . , 𝐴ℎ ) = (𝐵1 , . . . , 𝐵 𝑘 ), each component 𝐵 𝑗 ∈ P𝑛 (𝑆) is an 𝑛–level object determined by ℎ many 𝑚–level inputs. 245

247.

[beta]

Chapter 7. Extensional Definitions: (𝑚, 𝑛)-SuperHyperGraph
Table 7.1: Compact comparison: 𝑛-SuperHyperGraph vs. (𝑚, 𝑛)-SuperHyperGraph.
Item
Base data

𝑛-SuperHyperGraph
A finite base set 𝑉0 (universe for iterated powersets).
Supervertices are 𝑛-level objects:

Vertex type

𝑉 ⊆ P 𝑛 (𝑉0 ).

(𝑚, 𝑛)-SuperHyperGraph
A nonempty base set 𝑆 (universe for iterated
powersets).
Vertices
are
concrete
(𝑚, 𝑛)superhyperfunctions:
𝑉 ⊆ 𝔉𝑚,𝑛 (𝑆) := { 𝑓 : P𝑚 (𝑆) → P𝑛 (𝑆)}.

Edge / incidence model

Identifiers 𝐸 with an incidence map

Hyperedges are subsets of 𝑉:

𝜕 : 𝐸 → P (𝑉) \ {∅}.

What is “higher level”?

∅ ≠ E ⊆ P (𝑉) \ {∅}.

Typical reading

Higher level is in the objects (vertices live in
P 𝑛 (𝑉0 )).
Each
supervertex
represents
a
grouped/aggregated entity; each superedge
links multiple supervertices via incidence.

Specialization / relation

Recovers hypergraphs by restricting 𝑛 = 0 and
taking 𝑉 ⊆ 𝑉0 .

(Equivalently, one may encode each 𝐸 ∈ E
by an identifier plus an incidence map.)
Higher level is in the morphisms (vertices are
functions P𝑚 (𝑆) → P𝑛 (𝑆)).
Each vertex is a set-to-set transformer (rule,
policy, operator); each hyperedge groups several transformers to encode joint constraints
or contexts.
Extends the 𝑛-SuperHyperGraph viewpoint
by shifting vertices from 𝑛-level sets to (𝑚, 𝑛)level set-valued functions (Definition 7.1.3).

Definition 7.1.5 ((ℎ, 𝑘)-ary (𝑚, 𝑛)-SuperHyperGraph). [1084] Fix 𝑚, 𝑛, ℎ, 𝑘 ∈ N and 𝑆 ≠ ∅. Let
n
ℎ
𝑘 o
ℎ,𝑘
𝔉𝑚,𝑛
(𝑆) := 𝐹 : P𝑚 (𝑆) → P𝑛 (𝑆)
.
An (ℎ, 𝑘)-ary (𝑚, 𝑛)-SuperHyperGraph is a pair

(ℎ,𝑘 )
ℎ,𝑘
:= 𝑉, E ,
∅ ≠ 𝑉 ⊆ 𝔉𝑚,𝑛
(𝑆),
SHG (𝑚,𝑛)

∅ ≠ E ⊆ P (𝑉) \ {∅}.

For reference, the comparison between an (𝑚, 𝑛)-SuperHyperGraph and an (ℎ, 𝑘)-ary (𝑚, 𝑛)-SuperHyperGraph
is provided in Table 7.2.
Example 7.1.6 (Collaborative task planning: (ℎ, 𝑘, 𝑚, 𝑛) = (2, 2, 1, 1)). Let the base set of tasks be
𝑆 := {Doc, Code, Test, Deploy}.
Here P1 (𝑆) = P (𝑆) and outputs also lie in P1 (𝑆). Each vertex is a concrete (ℎ, 𝑘)-ary (𝑚, 𝑛)-superhyperfunction
2
2
𝐹 : P1 (𝑆) −→ P1 (𝑆) .
We interpret the inputs as two teams’ current selections 𝐴, 𝐵 ⊆ 𝑆, and the two outputs as Must Do and Plan
sets.
Define two vertices (set transformers):
𝐹ui ( 𝐴, 𝐵) := 𝐴 ∩ 𝐵, 𝐴 ∪ 𝐵



(consensus vs. union plan),

𝐹prio ( 𝐴, 𝐵) := ( 𝐴 ∪ 𝐵) ∩ 𝐶 , ( 𝐴 ∪ 𝐵) \ 𝐶 ★
with 𝐶 ★ := {Test, Deploy}.
★

Set
𝑉 := {𝐹ui , 𝐹prio },


E := {𝐹ui }, {𝐹prio }, {𝐹ui , 𝐹prio } .

Hyperedges encode whether one deploys only the union/intersection policy, only the priority split, or both
together.
Concrete input–output calculation. For team selections
𝐴 = {Doc, Test},

𝐵 = {Test, Code},
246

248.

[beta]

Chapter 7. Extensional Definitions: (𝑚, 𝑛)-SuperHyperGraph
Table 7.2: Compact comparison: (𝑚, 𝑛)-SuperHyperGraph vs. (ℎ, 𝑘)-ary (𝑚, 𝑛)-SuperHyperGraph.
Category

(𝑚, 𝑛)-SuperHyperGraph SHG (𝑚,𝑛) = (𝑉, E) (ℎ, 𝑘)-ary
(𝑚, 𝑛)-SuperHyperGraph
)
SHG (ℎ,𝑘
=
(𝑉,
E)
(𝑚,𝑛)

Underlying base data

A nonempty base set 𝑆 and two levels 𝑚, 𝑛 ∈ N. A nonempty base set 𝑆, levels 𝑚, 𝑛 ∈ N, and
arities ℎ, 𝑘 ∈ N.
Each vertex is a concrete (𝑚, 𝑛)- Each vertex is a concrete (ℎ, 𝑘)-ary (𝑚, 𝑛)superhyperfunction 𝑓 : P𝑚 (𝑆) → P𝑛 (𝑆).
superhyperfunction 𝐹 : (P𝑚 (𝑆)) ℎ →
(P𝑛 (𝑆)) 𝑘 .
Single 𝑚-level input set 𝐴 ∈ P𝑚 (𝑆) mapped to ℎ many 𝑚-level input sets ( 𝐴1 , . . . , 𝐴ℎ )
one 𝑛-level output set 𝑓 ( 𝐴) ∈ P𝑛 (𝑆).
mapped to a 𝑘-tuple of 𝑛-level outputs
𝐹 ( 𝐴1 , . . . , 𝐴ℎ ) = (𝐵1 , . . . , 𝐵 𝑘 ) with 𝐵 𝑗 ∈
P𝑛 (𝑆).
Unary rule/transformer on 𝑚-level objects pro- Multi-input, multi-output rule/transformer:
ducing one 𝑛-level object.
fuses ℎ sources (or contexts) and returns 𝑘 output channels.
∅ ≠ E ⊆ P (𝑉) \ {∅}; each hyperedge groups Same hyperedge formalism E ⊆ P (𝑉) \ {∅},
a finite nonempty set of vertices (functions) to but the grouped vertices are multi-ary, multioutput transformers.
encode higher-order relations/constraints.
Recovered as the case (ℎ, 𝑘) = (1, 1) of the Strictly generalizes (𝑚, 𝑛)-SuperHyperGraphs
arity-extended model.
by allowing ℎ ≠ 1 and/or 𝑘 ≠ 1.

Vertex meaning

Input-output interface

Interpretation

Hyperedges

Specialization

we obtain

𝐹ui ( 𝐴, 𝐵) = {Test}, {Doc, Test, Code} ,

𝐹prio ( 𝐴, 𝐵) = {Test}, {Doc, Code} .
)
= (𝑉, E) models two cooperative planning rules whose joint use is represented by the
Thus SHG (ℎ,𝑘
(𝑚,𝑛)
hyperedge {𝐹ui , 𝐹prio }.

Example 7.1.7 (Urban traffic response with detour bundles: (ℎ, 𝑘, 𝑚, 𝑛) = (3, 1, 1, 2)). Let the base set of road
segments be
𝑆 := {R1, R2, R3, R4, R5}.
Inputs are three incident reports 𝑋cam , 𝑋nav , 𝑋pol ⊆ 𝑆 from cameras, navigation apps, and police, respectively,
so the domain is (P1 (𝑆)) 3 . Outputs live in P2 (𝑆) = P (P (𝑆)), i.e., detour bundles (sets of candidate detour
sets).
Define two vertices:

𝐹cons (𝑋cam , 𝑋nav , 𝑋pol ) := 𝐶, (𝑈 \ 𝐶) \ {∅},
where 𝑈 := 𝑋cam ∪ 𝑋nav ∪ 𝑋pol , 𝐶 := (𝑋cam ∩ 𝑋nav ) ∪ (𝑋cam ∩ 𝑋pol ) ∪ (𝑋nav ∩ 𝑋pol ),
so 𝐶 aggregates segments supported by at least two sources (majority congestion) and 𝑈 \ 𝐶 are alternates; and
𝐹pairs (𝑋cam , 𝑋nav , 𝑋pol )
:=



𝑋cam ∩ 𝑋nav , 𝑋cam ∩ 𝑋pol , 𝑋nav ∩ 𝑋pol

\ {∅}.

Set

E := {𝐹cons }, {𝐹pairs }, {𝐹cons , 𝐹pairs } .

𝑉 := {𝐹cons , 𝐹pairs },

Hyperedges represent admissible joint deployment of consensus detouring and pairwise corroboration.
Concrete input–output calculation. For reports
𝑋cam = {R1, R2},

𝑋nav = {R2, R3},

𝑋pol = {R2, R4},

𝑋cam ∩ 𝑋pol = {R2},

𝑋nav ∩ 𝑋pol = {R2},

we compute 𝑈 = {R1, R2, R3, R4} and
𝑋cam ∩ 𝑋nav = {R2},

247

249.

[beta]

Chapter 7. Extensional Definitions: (𝑚, 𝑛)-SuperHyperGraph
so 𝐶 = {R2} and 𝑈 \ 𝐶 = {R1, R3, R4}. Hence
𝐹cons (𝑋cam , 𝑋nav , 𝑋pol ) =



{R2}, {R1, R3, R4} ,

𝐹pairs (𝑋cam , 𝑋nav , 𝑋pol ) =



{R2} .

(ℎ,𝑘 )
Therefore SHG (𝑚,𝑛)
= (𝑉, E) concretely captures multi-source incident fusion with outputs as detour bundles
in P2 (𝑆); their combined use is encoded by the hyperedge {𝐹cons , 𝐹pairs }.

7.2

Fuzzy (𝑚, 𝑛)-SuperHyperGraph

In this section we give a mathematically precise definition of a Fuzzy (𝑚, 𝑛)-SuperHyperGraph and prove
that it simultaneously generalizes (i) a fuzzy 𝑛-SuperHyperGraph and (ii) a (crisp) (𝑚, 𝑛)-SuperHyperGraph
(Definition 7.1.3). Throughout, 𝑆 ≠ ∅ is a fixed base set and 𝑚, 𝑛 ∈ N are fixed levels. We use the iterated
powerset notation

P0 (𝑆) := 𝑆,
P𝑡+1 (𝑆) := P P𝑡 (𝑆) (𝑡 ∈ N0 ).
Vertices of a (𝑚, 𝑛)-SuperHyperGraph are (𝑚, 𝑛)-superhyperfunctions 𝑓 : P𝑚 (𝑆) → P𝑛 (𝑆) (Definition 7.1.2).
Definition 7.2.1 (Fuzzy (𝑚, 𝑛)-SuperHyperGraph). Let SHG (𝑚,𝑛) = (𝑉,
 E) be a (crisp) (𝑚, 𝑛)-SuperHyperGraph
(Definition 7.1.3) with nonempty vertex set 𝑉 ⊆ Hom P𝑚 (𝑆), P𝑛 (𝑆) and nonempty family of nonempty hyperedges ∅ ≠ E ⊆ P (𝑉) \ {∅}. A Fuzzy (𝑚, 𝑛)-SuperHyperGraph on (𝑉, E) is a quadruple
𝔉 := (𝑉, E; 𝜎, 𝜇),
where
𝜎 : 𝑉 → [0, 1]

(vertex-membership),

𝜇 : E → [0, 1]

(hyperedge-membership)

satisfy the admissibility (edge–vertex) constraint
∀𝐸 ∈ E :

𝜇(𝐸) ≤ min 𝜎(𝑣).
𝑣 ∈𝐸

(7.1)

Equivalently, 𝜇(𝐸) ≤ 𝜎(𝑣) for every incident pair (𝑣, 𝐸) with 𝑣 ∈ 𝐸.
Optionally, one may introduce an incidence-membership map 𝜂 : 𝑉 × E → [0, 1] by the canonical choice
(
𝜇(𝐸), 𝑣 ∈ 𝐸,
𝜂(𝑣, 𝐸) :=
(7.2)
0,
𝑣 ∉ 𝐸,
which then satisfies the support equivalence [ 𝑣 ∈ 𝐸 ]
min{𝜎(𝑣), 𝜇(𝐸)} together with (7.1).

⇐⇒

𝜂(𝑣, 𝐸) > 0 and the bounds 𝜂(𝑣, 𝐸) ≤

Remark 7.2.2 (Simple/uniform restrictions). A Fuzzy (𝑚, 𝑛)-SuperHyperGraph is called simple if E has no
parallel hyperedges (i.e. distinct 𝐸, 𝐹 ∈ E have 𝐸 ≠ 𝐹), and 𝑘-uniform if |𝐸 | = 𝑘 for every 𝐸 ∈ E. Both
restrictions are orthogonal to fuzziness and can be assumed when convenient.

For reference, a comparison between the (𝑚, 𝑛)-SuperHyperGraph and the Fuzzy (𝑚, 𝑛)-SuperHyperGraph is
presented in Table 7.3.
Several illustrative examples are presented below.
Example 7.2.3 (E–commerce recommendation as a Fuzzy (𝑚, 𝑛)-SuperHyperGraph with (𝑚, 𝑛) = (1, 1)). Let
the base (item) set be
𝑆 := {Laptop, Phone, Headphones, Charger, Case}.
Here P1 (𝑆) = P (𝑆) and P𝑛 (𝑆) = P (𝑆) for 𝑛 = 1. A vertex 𝑓 ∈ 𝑉 is a concrete recommender
𝑓 : P (𝑆) −→ P (𝑆).
248

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Chapter 7. Extensional Definitions: (𝑚, 𝑛)-SuperHyperGraph
Table 7.3: Compact comparison: (𝑚, 𝑛)-SuperHyperGraph vs. Fuzzy (𝑚, 𝑛)-SuperHyperGraph.

Incidence viewpoint

(𝑚, 𝑛)-SuperHyperGraph (crisp)
A pair SHG (𝑚,𝑛) = (𝑉, E) with 𝑉 ⊆
Hom(P𝑚 (𝑆), P𝑛 (𝑆)) and ∅ ≠ E ⊆ P (𝑉) \ {∅}.
Elements 𝑣 ∈ 𝑉 are concrete (𝑚, 𝑛)superhyperfunctions 𝑣 : P𝑚 (𝑆) → P𝑛 (𝑆).
Each hyperedge is a nonempty set 𝐸 ∈ E with
𝐸 ⊆ 𝑉.
No membership constraints (crisp incidence is
𝑣 ∈ 𝐸).
Incidence is boolean: 𝑣 is incident to 𝐸 iff 𝑣 ∈ 𝐸.

Crisp reduction

Already crisp.

Modeling intent

Encodes higher-order relations among concrete
superhyperfunctions without uncertainty.

Aspect
Base data
Vertices
Hyperedges
Constraints

Fuzzy (𝑚, 𝑛)-SuperHyperGraph
A quadruple 𝔉 = (𝑉, E; 𝜎, 𝜇) on a fixed (𝑉, E),
where 𝜎 : 𝑉 → [0, 1] and 𝜇 : E → [0, 1].
Same vertex set 𝑉, but each vertex has a membership degree 𝜎(𝑣) ∈ [0, 1].
Same hyperedge family E, but each hyperedge
has a membership degree 𝜇(𝐸) ∈ [0, 1].
Admissibility (edge–vertex) constraint: 𝜇(𝐸) ≤
min𝑣 ∈𝐸 𝜎(𝑣) for all 𝐸 ∈ E (Definition 7.2.1).
Incidence can be encoded by the canonical map
𝜂(𝑣, 𝐸) = 𝜇(𝐸) if 𝑣 ∈ 𝐸, and 0 otherwise (optional), consistent with the admissibility bound.
If 𝜎, 𝜇 take only values in {0, 1} (and 𝜇(𝐸) =
1 implies 𝜎(𝑣) = 1 for all 𝑣 ∈ 𝐸), then 𝔉
reduces to a crisp (𝑚, 𝑛)-SuperHyperGraph on
the support.
Encodes graded reliability/importance of superhyperfunctions and of their grouped relations
via (𝜎, 𝜇).

Define two recommendation functions (vertices):
𝑓top (𝑋) := {Phone, Headphones} \ 𝑋 (bestseller filter, excluding already owned),


Ø
𝑓cb (𝑋) := 𝑋 ∪ sim(𝑥) \ 𝑋 (content–based expansion, then exclude 𝑋),
𝑥 ∈𝑋

where the similarity dictionary is fixed as
sim(Laptop) = {Charger}, sim(Phone) = {Charger, Case}, sim(Headphones) = {Case},
sim(Charger) = {Laptop, Phone}, sim(Case) = {Phone, Headphones}.
Set the vertex set and hyperedge family

E := { 𝑓top }, { 𝑓cb }, { 𝑓top , 𝑓cb } .

𝑉 := { 𝑓top , 𝑓cb },
Assign fuzzy memberships (model credibilities)

𝜎( 𝑓top ) = 0.86,

𝜎( 𝑓cb ) = 0.74,

and hyperedge-memberships

𝜇 { 𝑓top } = 0.86,


𝜇 { 𝑓cb } = 0.74,


𝜇 { 𝑓top , 𝑓cb } = 0.74.

Admissibility (edge–vertex) constraints (7.1) hold numerically:
𝜇({ 𝑓top }) = 0.86 ≤ min{0.86} = 0.86,

𝜇({ 𝑓cb }) = 0.74 ≤ min{0.74} = 0.74,

𝜇({ 𝑓top , 𝑓cb }) = 0.74 ≤ min{0.86, 0.74} = 0.74.
Concrete input–output illustration. For 𝑋 = {Laptop},
𝑓top (𝑋) = {Phone, Headphones},

𝑓cb (𝑋) = {Charger}.


With the canonical incidence-membership (7.2), we have, e.g., 𝜂 𝑓top , { 𝑓top , 𝑓cb } = 0.74 and 𝜂 𝑓cb , { 𝑓top } = 0.
Thus 𝔉 = (𝑉, E; 𝜎, 𝜇) is a valid Fuzzy (1, 1)-SuperHyperGraph for retail recommendations.
Example 7.2.4 (Smart-grid demand response as a Fuzzy (𝑚, 𝑛)-SuperHyperGraph with (𝑚, 𝑛) = (1, 2)). Let
the base (device) set be
𝑆 := {HVAC, EV, Washer, Dryer}.
249

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Chapter 7. Extensional Definitions: (𝑚, 𝑛)-SuperHyperGraph

Here P1 (𝑆) = P (𝑆) is the set of currently active devices, and P2 (𝑆) = P P (𝑆) is the set of curtailment group
candidates (each element is a subset of devices). A vertex 𝑓 ∈ 𝑉 maps an active-device set 𝑋 ⊆ 𝑆 to a family
of candidate curtailment groups 𝑓 (𝑋) ∈ P2 (𝑆):

𝑓 : P (𝑆) −→ P P (𝑆) .
Define two operational policies (vertices):

𝑓peak (𝑋) := {HVAC}, {EV}, 𝑋 ∩ {HVAC, EV} \ {∅},

𝑓balance (𝑋) := {Washer, Dryer}, 𝑋 ∩ {HVAC, Washer}, {EV, Washer}

\ {∅}.

Take

E := { 𝑓peak }, { 𝑓balance }, { 𝑓peak , 𝑓balance } .

𝑉 := { 𝑓peak , 𝑓balance },
Assign memberships (policy reliabilities)

𝜎( 𝑓peak ) = 0.83,
and hyperedge-memberships

𝜇 { 𝑓peak } = 0.83,

𝜎( 𝑓balance ) = 0.68,


𝜇 { 𝑓balance } = 0.68,


𝜇 { 𝑓peak , 𝑓balance } = 0.68.

Admissibility checks:
𝜇({ 𝑓peak }) = 0.83 ≤ min{0.83} = 0.83,

𝜇({ 𝑓balance }) = 0.68 ≤ min{0.68} = 0.68,

𝜇({ 𝑓peak , 𝑓balance }) = 0.68 ≤ min{0.83, 0.68} = 0.68.
Concrete input–output illustration. For the active set 𝑋 = {HVAC, Washer},


𝑓peak (𝑋) = {HVAC}, {EV}, {HVAC} = {HVAC}, {EV} ,

𝑓balance (𝑋) = {Washer, Dryer}, {HVAC, Washer}, {EV, Washer} .


With the canonical incidence-membership (7.2), 𝜂 𝑓peak , { 𝑓peak , 𝑓balance } = 0.68 and 𝜂 𝑓balance , { 𝑓peak } = 0,
matching support. Hence 𝔉 = (𝑉, E; 𝜎, 𝜇) is a Fuzzy (1, 2)-SuperHyperGraph modeling demand-response
policies with quantified confidence.
Theorem 7.2.5 (Embedding of fuzzy 𝑛-SuperHyperGraphs). Fix 𝑚 ∈ N and 𝑛 ∈ N0 . Every fuzzy 𝑛SuperHyperGraph (𝑊, F ; 𝜎𝑛 , 𝜇 𝑛 ) is (isomorphic to) a Fuzzy (𝑚, 𝑛)-SuperHyperGraph as in Definition 7.2.1.
Concretely, define the constant superhyperfunction embedding


𝜄 : 𝑊 ↩→ Hom P𝑚 (𝑆), P𝑛 (𝑆) ,
𝜄( 𝐴) (𝑋) := 𝐴 𝐴 ∈ 𝑊, 𝑋 ∈ P𝑚 (𝑆) .
Set
𝑉 ′ := 𝜄(𝑊),


E ′ := 𝜄[𝐹]

𝐹∈F

⊆ P (𝑉 ′ ) \ {∅},

and define 𝜎 ′ : 𝑉 ′ → [0, 1], 𝜇′ : E ′ → [0, 1] by pullback:
𝜎 ′ (𝜄( 𝐴)) := 𝜎𝑛 ( 𝐴),

𝜇′ (𝜄[𝐹]) := 𝜇 𝑛 (𝐹).

Then 𝔉′ := (𝑉 ′ , E ′ ; 𝜎 ′ , 𝜇′ ) is a Fuzzy (𝑚, 𝑛)-SuperHyperGraph and the map 𝜄 extends to an isomorphism of
fuzzy structures between (𝑊, F ; 𝜎𝑛 , 𝜇 𝑛 ) and 𝔉′ .
Proof. The map 𝜄 is injective by definition of constants. For 𝐸 ′ = 𝜄[𝐹] ∈ E ′ we have
min 𝜎 ′ (𝑣 ′ ) =

𝑣 ′ ∈𝐸 ′

min

𝜄 ( 𝐴) ∈ 𝜄[𝐹 ]

𝜎 ′ (𝜄( 𝐴)) = min 𝜎𝑛 ( 𝐴).
𝐴∈𝐹

Hence the admissibility constraint for 𝔉′ is
𝜇′ (𝐸 ′ ) = 𝜇 𝑛 (𝐹) ≤ min 𝜎𝑛 ( 𝐴) = min
𝜎 ′ (𝑣 ′ ),
′
′
𝐴∈𝐹

𝑣 ∈𝐸

. Thus 𝔉′ is a Fuzzy (𝑚, 𝑛)-SuperHyperGraph. The assignments 𝑊 ∋ 𝐴 ↦→ 𝜄( 𝐴) ∈ 𝑉 ′ and F ∋ 𝐹 ↦→ 𝜄[𝐹] ∈ E ′
yield a bijection preserving incidence, and the pullback definitions of 𝜎 ′ , 𝜇′ ensure preservation of membership
values. Therefore the two fuzzy structures are isomorphic.
□
250

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Chapter 7. Extensional Definitions: (𝑚, 𝑛)-SuperHyperGraph
We now show that the crisp structure is obtained as the {0, 1}-valued special case.
Theorem 7.2.6 (Crisp (𝑚, 𝑛)-SuperHyperGraphs are {0, 1}-valued fuzzy ones). Let SHG (𝑚,𝑛) = (𝑉, E) be a
(crisp) (𝑚, 𝑛)-SuperHyperGraph. Define
𝜎(𝑣) := 1

(∀𝑣 ∈ 𝑉),

𝜇(𝐸) := 1

(∀𝐸 ∈ E).

Then 𝔉 := (𝑉, E; 𝜎, 𝜇) is a Fuzzy (𝑚, 𝑛)-SuperHyperGraph. Moreover, if one also defines 𝜂 by (7.2), then
(
1, 𝑣 ∈ 𝐸,
𝜂(𝑣, 𝐸) =
0, 𝑣 ∉ 𝐸,
so the fuzzy incidence reduces to the crisp incidence relation.
Proof. For any 𝐸 ∈ E we have min𝑣 ∈𝐸 𝜎(𝑣) = min𝑣 ∈𝐸 1 = 1, hence (7.1) becomes 𝜇(𝐸) ≤ 1, which is
satisfied since 𝜇(𝐸) = 1. The formula for 𝜂 is immediate from (7.2).
□

251

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253.

Chapter 7. Extensional Definitions: (𝑚, 𝑛)-SuperHyperGraph 252

254.

[beta]

Chapter 8

SuperHyperStructure

Hyper- and SuperHyper-based viewpoints are not confined to graph models; they can be transferred to many
mathematical and real-world formalisms. In this chapter, we formalize the notions of HyperStructure and
SuperHyperStructure and outline several basic properties that motivate their use. Both HyperStructure
and SuperHyperStructure can be transformed into graph-based models, such as HyperGraphs (including
directed hypergraphs, bidirected hypergraphs, etc.) and SuperHyperGraphs (including directed SuperHyperGraphs, bidirected SuperHyperGraphs, etc.). Table 8.1 presents an overview of Structure, Hyperstructure,
𝑛-SuperHyperstructure, and (𝑚, 𝑛)-SuperHyperStructure.
Moreover, for reference, Tables 8.2, 8.3, and 8.4 present a comparison of classical, hyper-, and superhyperviewpoints across common domains. Research on HyperStructures and SuperHyperStructures is important
in that it has the potential to clarify the mathematical characteristics of such conceptual extensions and their
interrelationships.

8.1

HyperStructure

We use the phrase classical structure for a standard mathematical (or application-driven) framework arising,
for example, in logic, probability, statistics, algebra, geometry, graph theory, automata, or game theory
[1200,1205,1206]. A hyperstructure broadens such a framework by replacing a base set 𝑆 with its powerset P (𝑆)
and by permitting hyperoperations whose outputs are subsets rather than single elements. This replacement
makes it possible to encode multi-valued and higher-order interactions among elements [1207–1209]. We now
state precise definitions.
Definition 8.1.1 (Classical Structure). [814] A Classical Structure is a structured object from a standard
domain such as set theory, logic, probability, statistics, algebra, geometry, graph theory, automata theory, or
game theory. Formally, it is a pair

C = 𝐻, {# (𝑚) } 𝑚∈ I ,
where:
• 𝐻 is a nonempty carrier (underlying) set;
• for each 𝑚 ∈ I ⊆ Z>0 , there is an 𝑚-ary operation # (𝑚) : 𝐻 𝑚 → 𝐻 satisfying the axioms required by
the intended context (e.g., associativity, commutativity, identity elements, inverses, etc.).
We say that C is of type {# (𝑚) : 𝑚 ∈ I}. Representative examples include:
• Set: (𝑆, ∅), where 𝑆 may additionally carry designated elements, relations, or constants [105].
• Logic: (𝐿, ∧, ∨, ¬) with binary connectives ∧, ∨ and unary negation ¬, satisfying the usual logical
laws [1210].
253

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Chapter 8. SuperHyperStructure
Table 8.1:
Concise overview of Structure, Hyperstructure, 𝑛-SuperHyperstructure, and (𝑚, 𝑛)SuperHyperStructure.
Model
Structure

Carrier
Nonempty set 𝐻.

Operation(s) and type
Main viewpoint / typical use
𝑚-ary operations # (𝑚) : 𝐻 𝑚 → Base-level single-valued inter𝐻 (𝑚 ∈ I ⊆ Z>0 ). Single- actions (algebra, logic, probability, graphs, automata,
valued outputs.
games, etc.).
interactions:
Hyperstructure
Powerset P (𝑆) (often Set-valued operation, e.g. ◦ : Multi-valued
nonempty subsets).
𝑆 × 𝑆 → P (𝑆), or an operation outputs are subsets rather than
on subsets ◦ : P (𝑆) × P (𝑆) → single elements.
P (𝑆).
𝑛Iterated powerset P 𝑛 (𝑆) Operation on the 𝑛-level layer, Nested (hierarchical) collecSuperHyperstructure
(𝑛 ≥ 1).
e.g. ◦ : (P 𝑛 (𝑆)) 𝑠 → P 𝑛 (𝑆) tions up to depth 𝑛; layered
relations or hierarchical uncer(𝑠 ≥ 1).
tainty.
(𝑚, 𝑛)Domain layer P 𝑚 (𝑆) Superhyper-operation (arity 𝑠): Unified viewpoint: classiSuperHyperStructure
and codomain layer ⊙ (𝑚,𝑛) : (P 𝑚 (𝑆)) 𝑠 → P 𝑛 (𝑆) cal/hyper/iterated layers and
P 𝑛 (𝑆).
(𝑚, 𝑛 ≥ 0). Special cases: (0, 0) cross-level mappings between
classical; (0, 1) hyper; (𝑚, 𝑚) them.
within-layer.

• Probability: (Ω, F , 𝑃), where 𝑃 : F → [0, 1] is a probability measure on a 𝜎-algebra F ⊆ P (Ω) [1211].
• Statistics: (𝑋, A, 𝜃), where 𝜃 associates observed data (or statistics) to parameters of interest [1212].
• Algebra:
– Group (𝐺, ∗) with binary operation ∗ : 𝐺 × 𝐺 → 𝐺 satisfying the group axioms [1213, 1214];
– Ring (𝑅, +, ×) with two binary operations satisfying the ring axioms [1196, 1215];
– Vector space (𝑉, +, ·) over a field F with scalar multiplication · : F × 𝑉 → 𝑉 [1216, 1217].
• Geometry: (𝑋, dist) with a metric dist : 𝑋 × 𝑋 → R [1218, 1219].
• Graph: (𝑉, 𝐸) with 𝐸 ⊆ {{𝑢, 𝑣} : 𝑢, 𝑣 ∈ 𝑉 } in the undirected case, or 𝐸 ⊆ 𝑉 × 𝑉 in the directed case;
adjacency and incidence are defined in the usual way [1, 17].
• Automaton: (𝑄, Σ, 𝛿, 𝑞 0 , 𝐹), where 𝑄 is a finite state set, Σ is the input alphabet, 𝛿 : 𝑄 × Σ → 𝑄 is the
transition function, 𝑞 0 ∈ 𝑄 is the initial state, and 𝐹 ⊆ 𝑄 is the set of accepting states [1220, 1221].
• Game: (𝑁, {𝐴𝑖 }𝑖 ∈ 𝑁 , {𝑢 𝑖 }𝑖 ∈ 𝑁 ), where 𝑁 is the player set, 𝐴𝑖 is the action set of player 𝑖, and 𝑢 𝑖 :
Î
𝑗 ∈ 𝑁 𝐴 𝑗 → R is the payoff function of player 𝑖 [1222, 1223].
Definition 8.1.2 (Hyperoperation). (cf. [1224, 1225]) Let 𝑆 be a set. A hyperoperation on 𝑆 is a binary rule
whose output is a subset of 𝑆 (possibly a singleton), namely a map
◦ : 𝑆 × 𝑆 −→ P (𝑆).
Thus for (𝑥, 𝑦) ∈ 𝑆 × 𝑆, the value 𝑥 ◦ 𝑦 is a (possibly multi-element) subset of 𝑆.
Definition 8.1.3 (Hyperstructure). (cf. [1198, 1226, 1227]) A Hyperstructure is obtained by lifting a classical
structure to the powerset level. Concretely, it can be presented in the form

H = P (𝑆), ◦ ,
where ◦ is a hyperoperation on 𝑆 (or, more generally, an operation acting on subsets). In this setting, the
basic operations take collections of elements as inputs and return collections as outputs, thereby encoding
multi-valued interactions.
Example 8.1.4 (Hyperstructure induced by a group operation). Let (𝐺, ∗) be a (classical) group with carrier
set 𝐺 ≠ ∅ and binary operation ∗ : 𝐺 × 𝐺 → 𝐺. Define a hyperoperation
◦ : P (𝐺) × P (𝐺) −→ P (𝐺)
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256.

Chapter 8. SuperHyperStructure Table 8.2: Keyword-style comparison of classical, hyper-, and superhyper- viewpoints across common domains (Part 1). Domain Graph theory Directed graphs Functions Algebra Topology Groups Games Probability Entropy Chemistry Automata Classical Graph [3] Digraph [468] Function [1089, 1090] HyperHypergraph [17, 1081, 1086] DiHypergraph [1087, 1088] Hyperfunction [115] SuperHyper𝑛-SuperHyperGraph [2] DiSuperHyperGraph [801] SuperHyperfunction [115, 1091] Algebra [1092, 1093] Hyperalgebra [1094, 1095] SuperHyperalgebra [1096–1098] Topology [1099, 1100] Hypertopology [1101] SuperHypertopology [1102, 1103] Group [1104, 1105] Hypergroup [1106, 1107] SuperHypergroup [1108] Game [1109, 1110] Hypergame [1111] SuperHypergame [1111] Probability [1112, 1113] Hyperprobability [1114] SuperHyperprobability [1114] Entropy [1115, 1116] Hyperentropy [1117] SuperHyperentropy [1117] Chemical structure Chemical hyperstruc- Chemical superhyperstructure [1118, 1119] ture [1120–1122] [1123] Automaton [1124, 1125] Hyperautomaton [1126, 1127] Superhyperautomaton [1126, 1127] by the setwise product 𝐴 ◦ 𝐵 := { 𝑎 ∗ 𝑏 : 𝑎 ∈ 𝐴, 𝑏 ∈ 𝐵 } ⊆ 𝐺 ( 𝐴, 𝐵 ⊆ 𝐺). Then H = P (𝐺), ◦ is a hyperstructure in the sense of Definition (Hyperstructure). Indeed, the carrier is the powerset P (𝐺), and the operation ◦ takes two collections of group elements and returns the collection of all possible products formed by choosing one element from each input set. For instance, if 𝐴 = {𝑔1 , 𝑔2 } and 𝐵 = {ℎ1 }, then 𝐴 ◦ 𝐵 = {𝑔1 ∗ ℎ1 , 𝑔2 ∗ ℎ1 }. Thus the operation encodes a multi-valued interaction: a single pair of sets ( 𝐴, 𝐵) produces (in general) many outcomes in 𝐺. Example 8.1.5 (Reachability hyperstructure on a directed graph). Let 𝐷 = (𝑉, 𝐸) be a directed graph with vertex set 𝑉 ≠ ∅ and edge set 𝐸 ⊆ 𝑉 × 𝑉. For 𝑢 ∈ 𝑉, write 𝑁 + (𝑢) := { 𝑣 ∈ 𝑉 : (𝑢, 𝑣) ∈ 𝐸 } for the (out-)neighborhood of 𝑢. Define a hyperoperation ◦ : P (𝑉) × P (𝑉) −→ P (𝑉) by 𝐴 ◦ 𝐵 := { 𝑣 ∈ 𝑉 : ∃ 𝑢 ∈ 𝐴 with 𝑣 ∈ 𝑁 + (𝑢) } ∪ 𝐵 ( 𝐴, 𝐵 ⊆ 𝑉). Equivalently, 𝐴 ◦ 𝐵 consists of all vertices reachable from 𝐴 by one directed edge, together with all vertices already listed in 𝐵. Then H = P (𝑉), ◦ is a hyperstructure: the carrier is P (𝑉), and ◦ maps a pair of vertex-collections to a new vertex-collection. Concretely, if 𝐴 = {𝑢 1 , 𝑢 2 } and 𝐵 = {𝑤}, then 𝐴 ◦ 𝐵 = 𝑁 + (𝑢 1 ) ∪ 𝑁 + (𝑢 2 ) ∪ {𝑤}, which aggregates multiple possible next-step vertices at once. Hence ◦ captures multi-valued dynamics (many possible next states) in a single set-valued operation. 255

257.

[beta]

Chapter 8. SuperHyperStructure
Table 8.3: Keyword-style comparison across additional domains (Part 2).
Domain
Language

Classical
HyperSuperHyperLanguage
structure Hyperlanguage
struc- SuperHyperlanguage structure
[1128, 1129]
ture [1130, 1131]
[1130, 1131]
Geometry [1132, Geometric structure
Hypergeometric
struc- SuperHypergeometric struc1133]
ture [1134]
ture [1135, 1136]
Meta
Meta-structure [1137]
Meta-hyperstructure [1137]
Meta-superhyperstructure
[1137]
Medicine [1138] Medical structure
Medical hyperstructure [39]
Medical Superhyperstructure
[39]
Randomness
Random structure
Hyperrandom structure [1140] SuperHyperrandom structure
[1139]
[1140]
Decision-making Decision structure [1143]
Hyperdecision structure [1144] SuperHyperdecision structure
[1141, 1142]
[1144]
Category
the- Category [1146, 1147]
Hypercategory [1148]
SuperHypercategory [1148]
ory [1145]
Variables
Variable
Hypervariable [1140]
SuperHypervariable [1140]
Integral
Integral structure [1149, 1150] Hyperintegral structure [1151] SuperHyperintegral structure
[1151]
Space
Space
Hyperspace [1151]
SuperHyperspace [1151]

8.2

SuperHyperStructure

A SuperHyperStructure strengthens the above idea by iterating the powerset construction a prescribed number
of times. One then works with nested families of subsets, and operations act across these nested tiers, which
naturally models hierarchical and multi-layer interactions [114, 1228, 1229]. This viewpoint supports notions
such as SuperHyperAlgebra [1230, 1231], SuperHyperGraph [16, 107, 1232], and other super-level algebraic
and combinatorial systems.
Definition 8.2.1 (SuperHyperOperations). (cf. [1198]) Let 𝐻 ≠ ∅, and let P 𝑘 (𝐻) denote the 𝑘-fold iterated
powerset of 𝐻 (as defined in the preliminaries). An (𝑚, 𝑛)-SuperHyperOperation is an 𝑚-ary mapping
◦ (𝑚,𝑛) : 𝐻 𝑚 −→ P∗𝑛 (𝐻),
where P∗𝑛 (𝐻) denotes either the full 𝑛-th iterated powerset P 𝑛 (𝐻) or the corresponding nonempty subfamily
P 𝑛 (𝐻)\{∅}. If ∅ is excluded we call the operation classical-type, whereas allowing ∅ yields a neutrosophic-type
SuperHyperOperation.
Definition 8.2.2 (𝑛-Superhyperstructure). (cf. [114, 1198, 1233, 1234]) Let 𝑆 ≠ ∅ and fix 𝑛 ∈ N. An 𝑛Superhyperstructure on 𝑆 is a hyperstructure whose carrier is the 𝑛-fold iterated powerset:

SH 𝑛 = P 𝑛 (𝑆), ◦ ,
where ◦ is an operation (possibly multi-valued) acting on P 𝑛 (𝑆). Equivalently, SH 𝑛 records interactions
among nested collections of subsets up to depth 𝑛.
Definition 8.2.3 (SuperHyperStructure of order (𝑚, 𝑛)). (cf. [115, 1229]) Let 𝑆 ≠ ∅ and let 𝑚, 𝑛 ≥ 0. A
(𝑚, 𝑛)-SuperHyperStructure (of arity 𝑠) is specified by a map
⊙ (𝑚,𝑛) : P 𝑚 (𝑆)

𝑠

−→ P 𝑛 (𝑆).

This unifies several standard situations:
• 𝑚 = 𝑛 = 0 recovers ordinary 𝑠-ary operations on 𝑆;
• 𝑚 = 0 and 𝑛 = 1 yields (set-valued) hyperoperations on 𝑆;
• 𝑠 = 1 gives a (super)operation acting on a single input from P 𝑚 (𝑆).
256

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Chapter 8. SuperHyperStructure
Table 8.4: Keyword-style comparison across uncertainty/set- and algebra-oriented domains (Part 3).
Domain
Fuzzy set
Weighted set
Vague set
Neutrosophic set
Plithogenic set
Uncertain set
Rough sets
Soft sets
Z-number
Partition
Matrix
Cognitive map
Floorplan
Code
Ring
Field
Lattice

Classical
Fuzzy set [746, 1152]

HyperHyperfuzzy set [1153–1155]

SuperHyperSuperHyperfuzzy set [1156–
1158]
Weighted set
Hyperweighted set [372, 1159] SuperHyperweighted set [372,
1159]
Vague set [1160, 1161]
Hypervague set [1162]
SuperHypervague set [1162]
Neutrosophic set [800, 831, Hyperneutrosophic set [1164, SuperHyperneutrosophic
1163]
1165]
set [1158, 1166]
Plithogenic set [809, 1167]
Hyperplithogenic set [1168– SuperHyperplithogenic
1170]
set [1158, 1166]
Uncertain set [814]
Hyperuncertain set [814,1158] SuperHyperuncertain set [814,
1158]
Rough set [906, 1171]
Hyperrough set [1166, 1172, SuperHyperrough set [1166,
1173]
1174]
Soft set [890, 891]
Hypersoft set [1166, 1175]
SuperHypersoft
set
[1166, 1176–1178]
Z-number [1179–1181]
Hyper Z-number [1182]
SuperHyper Z-number [1182]
Partition
Hyperpartition [1151]
SuperHyperpartition [1151]
Matrix [1183–1185]
Hypermatrix [1140, 1186]
SuperHypermatrix
[1140, 1187]
Cognitive map [1188–1190]
Cognitive Hypermap [1140]
Cognitive
SuperHypermap [1140]
Floorplan [1191, 1192]
Hyperfloorplan [1193]
SuperHyperfloorplan [1193]
Code
Hypercode [1193]
SuperHypercode [1193]
Ring [1194, 1195]
Hyperring [1196, 1197]
SuperHyperring [1198]
Field [1199]
HyperField [1197, 1200, 1201] SuperHyperField [1140]
Lattice [546, 547, 1202]
Hyperlattice [1140,1203,1204] SuperHyperlattice [1140]

Hence (𝑚, 𝑛)-SuperHyperStructures provide a common language for classical, hyper-, and multi-level superhyper constructions.
Example 8.2.4 (A (0, 2)-SuperHyperStructure: “two-level recommendation bundle”). Let 𝑆 be a nonempty
set of items (e.g., products in an online catalog). We define a (0, 2)-SuperHyperStructure of arity 𝑠 = 2 by the
mapping

⊙ (0,2) : 𝑆 2 −→ P 2 (𝑆),
(𝑥, 𝑦) ↦−→ {𝑥}, {𝑦}, {𝑥, 𝑦} .
Here P 2 (𝑆) = P (P (𝑆)) is the set of families of subsets of 𝑆. For an ordered pair (𝑥, 𝑦), the output

⊙ (0,2) (𝑥, 𝑦) = {𝑥}, {𝑦}, {𝑥, 𝑦} ∈ P (P (𝑆))
is a two-level object: it is a set whose elements are subsets of 𝑆. In words, the operation returns a nested bundle
consisting of the singleton recommendations {𝑥} and {𝑦} and the joint bundle {𝑥, 𝑦}. Therefore ⊙ (0,2) is a
concrete example of a SuperHyperStructure map of order (𝑚, 𝑛) = (0, 2).
(If one wishes to exclude the empty set at every level, one may instead regard the codomain as P 2 (𝑆) \ {∅};
the above output is already nonempty.)
Example 8.2.5 (A (1, 1)-SuperHyperStructure: “closure under pairwise fusion”). Let 𝑆 be a nonempty set,
and consider the arity 𝑠 = 2 mapping
⊙ (1,1) : P (𝑆)

2

−→ P (𝑆),

( 𝐴, 𝐵) ↦−→ 𝐴 ∪ 𝐵 ∪ ( 𝐴 ∗ 𝐵),

where ∗ is an auxiliary operation on subsets defined by
𝐴 ∗ 𝐵 := { 𝑎 ∗𝑆 𝑏 : 𝑎 ∈ 𝐴, 𝑏 ∈ 𝐵 } ⊆ 𝑆,
and ∗𝑆 : 𝑆 × 𝑆 → 𝑆 is any fixed binary operation on 𝑆 (for instance, addition on a group, multiplication on a
ring, or concatenation on a free monoid).
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Chapter 8. SuperHyperStructure Then, for any 𝐴, 𝐵 ⊆ 𝑆, the value ⊙ (1,1) ( 𝐴, 𝐵) is a subset of 𝑆, hence an element of P (𝑆). The three components have the following meanings: 𝐴 (keep the first input), 𝐵 (keep the second input), 𝐴∗𝐵 (all pairwise fusions under ∗𝑆 ). Thus ⊙ (1,1) takes two first-level collections (elements of P (𝑆)) and returns a first-level collection (again in P (𝑆)) obtained by closing under pairwise fusion and union. This is a concrete SuperHyperStructure of order (𝑚, 𝑛) = (1, 1), and it illustrates that (𝑚, 𝑛)-SuperHyperStructures can model operations acting directly on sets of objects, not only on individual objects. 258

260.

Chapter 9 Conclusion In this book, we extended the framework by introducing Fuzzy (𝑚, 𝑛)-SuperHyperGraphs, where fuzzy memberships are incorporated into both vertices and hyperedges. For future work, we aim to explore further generalizations using other fuzzy and uncertainty-based graph models, such as Intuitionistic Fuzzy Graphs [1235, 1236], Hesitant Fuzzy Graphs [754, 1237], Bipolar Fuzzy Graphs [758, 1238], Neutrosophic Graphs [64, 65, 1239], and Plithogenic Graphs [69, 1240]. These directions hold promise for developing richer models capable of handling diverse forms of uncertainty and contradiction in real-world applications. 259

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Chapter 9. Conclusion 260

262.

Disclaimer Funding This study did not receive any financial or external support from organizations or individuals. Acknowledgments We extend our sincere gratitude to everyone who provided insights, inspiration, and assistance throughout this research. We particularly thank our readers for their interest and acknowledge the authors of the cited works for laying the foundation that made our study possible. We also appreciate the support from individuals and institutions that provided the resources and infrastructure needed to produce and share this book. Finally, we are grateful to all those who supported us in various ways during this project. Data Availability This research is purely theoretical, involving no data collection or analysis. We encourage future researchers to pursue empirical investigations to further develop and validate the concepts introduced here. Ethical Approval As this research is entirely theoretical in nature and does not involve human participants or animal subjects, no ethical approval is required. Use of Generative AI and AI-Assisted Tools I use generative AI and AI-assisted tools for tasks such as English grammar checking, and I do not employ them in any way that violates ethical standards. Conflicts of Interest The authors confirm that there are no conflicts of interest related to the research or its publication. Disclaimer This work presents theoretical concepts that have not yet undergone practical testing or validation. Future researchers are encouraged to apply and assess these ideas in empirical contexts. While every effort has been made to ensure accuracy and appropriate referencing, unintentional errors or omissions may still exist. Readers are advised to verify referenced materials on their own. The views and conclusions expressed here are the authors’ own and do not necessarily reflect those of their affiliated organizations. 261

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Chapter 9. Conclusion 262

264.

Appendix A Appendix: Multi-Intersection Graph A multi-intersection graph is the intersection graph of a multiset of sets, allowing repeated identical sets as distinct vertices [1241]. Definition A.0.1 (Intersection graph of a finite family). Let 𝑆 be a set and let F be a finite family of subsets of 𝑆. The intersection graph of F , denoted by (F ), is the (simple) graph with vertex set 𝑉 (F ) = F , and with an edge 𝐴𝐵 between two distinct vertices 𝐴, 𝐵 ∈ F if and only if 𝐴 ∩ 𝐵 ≠ ∅. Definition A.0.2 (Intersection graph of a finite multiset). Let 𝑆 be a set and let 𝐹 be a finite multiset [1242] of subsets of 𝑆. Formally, write 𝐹 as a finite list 𝐹 = {𝐴1 , . . . , 𝐴 𝑁 } ( 𝐴𝑖 ⊆ 𝑆), allowing repetitions. The intersection graph (𝐹) is the simple graph with vertex set 𝑉 (𝐹) = {1, . . . , 𝑁 }, and an edge 𝑖 𝑗 for 𝑖 ≠ 𝑗 if and only if 𝐴𝑖 ∩ 𝐴 𝑗 ≠ ∅. (Thus, if 𝐴𝑖 = 𝐴 𝑗 ≠ ∅ with 𝑖 ≠ 𝑗, then 𝑖 𝑗 is an edge.) Definition A.0.3 (Reduction of a multiset). Let 𝐹 be a finite multiset of subsets of a set 𝑆. The reduction of 𝐹, denoted by [𝐹], is the set obtained from 𝐹 by keeping exactly one representative of each distinct subset occurring in 𝐹. Equivalently, [𝐹] is the set of distinct elements appearing in the multiset 𝐹. Definition A.0.4 (Multi-intersection graph classes 𝑃𝑚 and 𝑃∗ ). [1241] Fix a hereditary class 𝑃 = 𝑃1 of intersection graphs, described by a hereditary predicate on finite set families (equivalently: 𝑃 is closed under induced subgraphs). Let 𝐹 be a finite multiset of subsets of some ground set. 1. 𝑃∗ is the class of all graphs (𝐹) such that [𝐹] belongs to the underlying family domain and the reduced family satisfies the predicate of 𝑃, i.e. 𝑃( [𝐹]) = 1. 2. For an integer 𝑚 ≥ 1, 𝑃𝑚 is the class of all graphs (𝐹) such that every subset appears in 𝐹 with multiplicity at most 𝑚, and 𝑃( [𝐹]) = 1. Graphs in 𝑃∗ (resp. 𝑃𝑚 ) are called multi-intersection graphs (resp. 𝑚-multi-intersection graphs) with respect to the base class 𝑃. Remark A.0.5 (Equivalent “vertex duplication” view). Let 𝑃 be a hereditary class of graphs. A graph lies in 𝑃𝑚 exactly when it can be obtained from some 𝐺 ∈ 𝑃 by replacing each vertex 𝑣 ∈ 𝑉 (𝐺) by a clique of size 𝑚(𝑣) with 1 ≤ 𝑚(𝑣) ≤ 𝑚, and keeping adjacency between cliques according to adjacency of the original vertices. For 𝑃∗ one allows arbitrary finite clique sizes. As one example, we extend string graphs and interval graphs to multi-string graphs and multi-interval graphs. A string graph is the intersection graph of a family of curves in the plane: each vertex represents one curve, and two vertices are adjacent exactly when the corresponding curves intersect [509, 1243–1245]. As superclasses of string graphs, families such as VPG [1246] and 𝑘-SEG graphs [1247] are known. As subclasses of string graphs, planar graphs and circular permutation graphs [1248] are known. An interval graph is the intersection graph of a family of intervals on the real line: each vertex represents one interval, and two vertices are adjacent exactly when the corresponding intervals overlap (have nonempty intersection). 263

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[beta]

Appendix A. Appendix: Multi-Intersection Graph
Definition A.0.6 (String and string graph). [509, 1243–1245] A string is a continuous map 𝛾 : [0, 1] → R2 ;
we identify it with its image 𝛾([0, 1]) ⊆ R2 . A simple graph 𝐺 = (𝑉, 𝐸) is a string graph if there exists a
family of strings {𝛾𝑣 } 𝑣 ∈𝑉 in the plane such that for all distinct 𝑢, 𝑣 ∈ 𝑉,
𝑢𝑣 ∈ 𝐸

⇐⇒

𝛾𝑢 ( [0, 1]) ∩ 𝛾𝑣 ( [0, 1]) ≠ ∅.

Definition A.0.7 (MultiString graph). A simple graph 𝐺 is a multi-string graph if there exists a finite multiset
𝐹 of strings in the plane such that 𝐺  (𝐹). Equivalently, 𝐺 is the intersection graph of a multiset of planar
strings, where multiple vertices are allowed to correspond to identical strings.
Definition A.0.8 (Interval graph). A simple graph 𝐺 = (𝑉, 𝐸) is an interval graph if there exists an assignment
𝑣 ↦→ 𝐼 𝑣 of a nonempty real interval 𝐼 𝑣 ⊆ R to each vertex 𝑣 ∈ 𝑉 such that for all distinct 𝑢, 𝑣 ∈ 𝑉,
𝑢𝑣 ∈ 𝐸

⇐⇒

𝐼𝑢 ∩ 𝐼 𝑣 ≠ ∅.

Definition A.0.9 (MultiInterval graph). A simple graph 𝐺 is a multi-interval graph if there exists a finite
multiset 𝐹 of nonempty real intervals such that 𝐺  (𝐹). Equivalently, 𝐺 is the intersection graph of a multiset
of intervals, allowing repeated use of the same interval.
We state the theorem below.
Theorem A.0.10 (MultiInterval graphs are multi-intersection graphs). Let 𝑃 be the hereditary class of all
interval graphs. Then every multi-interval graph belongs to the multi-intersection class 𝑃∗ . More precisely, if
𝐺 is the intersection graph of a multiset of intervals, then 𝐺 ∈ 𝑃∗ with respect to 𝑃.
Proof. Let 𝐺  (𝐹) where 𝐹 = {𝐼1 , . . . , 𝐼 𝑁 } is a finite multiset of nonempty real intervals. Let [𝐹] =
{𝐽1 , . . . , 𝐽𝑡 } be the set of distinct intervals appearing in 𝐹.
Consider the intersection graph 𝐻 := ( [𝐹]) of the set [𝐹]. By definition of interval graphs, 𝐻 is an interval
graph: it is realized by the interval family {𝐽1 , . . . , 𝐽𝑡 }, so 𝐻 ∈ 𝑃.
Now compare (𝐹) and ( [𝐹]): for each distinct interval 𝐽ℓ occurring in 𝐹, let 𝑚 ℓ ≥ 1 be its multiplicity. In
(𝐹), the vertices corresponding to the 𝑚 ℓ copies of 𝐽ℓ form a clique (because 𝐽ℓ ∩ 𝐽ℓ = 𝐽ℓ ≠ ∅), and they
have identical adjacency to vertices coming from other intervals (because intersection depends only on the
underlying interval). Hence (𝐹) is obtained from 𝐻 = ( [𝐹]) by replacing each vertex 𝐽ℓ by a clique of size 𝑚 ℓ
and preserving adjacencies between cliques.
Therefore 𝐺  (𝐹) ∈ 𝑃∗ by the definition of 𝑃∗ (equivalently, by the vertex-duplication characterization of
multi-intersection classes).
□
Theorem A.0.11 (MultiString graphs are multi-intersection graphs). Let 𝑃 be the hereditary class of all string
graphs. Then every multi-string graph belongs to the multi-intersection class 𝑃∗ .
Proof. Let 𝐺  (𝐹) where 𝐹 = {𝛾1 , . . . , 𝛾 𝑁 } is a finite multiset of planar strings. Let [𝐹] = {𝜂1 , . . . , 𝜂𝑡 } be
the set of distinct strings appearing in 𝐹, and put 𝐻 := ( [𝐹]).
By definition of string graphs, 𝐻 is a string graph, since it is realized by the string family {𝜂1 , . . . , 𝜂𝑡 }; hence
𝐻 ∈ 𝑃.
As in the interval case, duplicates behave as vertex duplications: if a string 𝜂ℓ appears with multiplicity 𝑚 ℓ ≥ 1
in 𝐹, then the corresponding 𝑚 ℓ vertices form a clique in (𝐹) whenever 𝜂ℓ ( [0, 1]) ≠ ∅ (always true), and they
have identical neighborhoods outside the clique because intersections with any other string depend only on the
underlying set 𝜂ℓ ( [0, 1]). Thus (𝐹) is obtained from 𝐻 by replacing each vertex by a clique (of size equal to
its multiplicity) and preserving adjacencies between cliques.
Hence 𝐺 ∈ 𝑃∗ by the definition of multi-intersection classes.

264

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Appendix (List of Tables) 1.1 1.2 1.3 Key distinctions among graph, hypergraph, and superhypergraph . . . . . . . . . . . . . . . . Applied graph, hypergraph, and superhypergraph models . . . . . . . . . . . . . . . . . . . . Additional applied graph, hypergraph, and superhypergraph models (Part 2) . . . . . . . . . . 7 8 8 2.1 Conceptual relationships among Graphs, HyperGraphs, and SuperHyperGraphs . . . . . . . . 12 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 Comparison of graph, hypergraph, and SuperHyperGraph products . . . . . . . . . . . . . . . Comparison of Graph Entropy, HyperGraph Entropy, and SuperHyperGraph Entropy . . . . . Comparison of Similarity and Metric on HyperGraphs and on SuperHyperGraphs . . . . . . . Comparison of Hypergraph morphisms and SuperHyperGraph morphisms . . . . . . . . . . . Comparison of Graph, HyperGraph, and SuperHyperGraph Partitioning . . . . . . . . . . . . Comparison of Graph Coloring, HyperGraph Coloring, and SuperHyperGraph Coloring . . . Comparison of graph, hypergraph, and superhypergraph domination . . . . . . . . . . . . . . Comparison of Sombor index for graphs, hypergraphs, and superhypergraphs . . . . . . . . . 28 32 34 36 38 41 45 48 4.1 4.2 Comparison of directed graphs, directed hypergraphs, and directed 𝑛-SuperHyperGraphs . . . 59 Concise overview of bidirected graphs, bidirected hypergraphs, and bidirected SuperHyperGraphs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 4.3 Concise overview of undirected, directed, bidirected, and multidirected graphs. . . . . . . . . 62 4.4 Concise overview of multidirected graphs, multidirected hypergraphs, and multidirected 𝑛SuperHyperGraphs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 4.5 Overview of SemiGraphs, SemiHyperGraphs, and Semi 𝑛-SuperHyperGraphs . . . . . . . . . 69 4.6 Comparison of signed graphs, signed hypergraphs, and signed 𝑛-SuperHyperGraphs . . . . . . 75 4.7 Comparison of weighted graphs, weighted hypergraphs, and weighted SuperHyperGraphs . . . 77 4.8 Concise overview of tree, hypertree, and superhypertree decompositions. . . . . . . . . . . . . 82 4.9 Comparison of interval graphs, interval hypergraphs, and interval 𝑛-SuperHyperGraphs . . . . 97 4.10 Concise comparison of unimodular hypergraphs and unimodular 𝑛-SuperHyperGraphs. . . . . 100 4.11 Comparison of probabilistic graphs, probabilistic hypergraphs, and probabilistic 𝑛-SuperHyperGraphs105 4.12 Concise comparison of balanced hypergraphs and balanced 𝑛-SuperHyperGraphs. . . . . . . . 106 4.13 Concise comparison of planar graphs, planar hypergraphs, and planar 𝑛-SuperHyperGraphs. . 111 4.14 Concise overview of Meta-Graph, Meta-HyperGraph, and Meta-SuperHyperGraph. . . . . . . 123 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 Classical and uncertain Graph models with membership relations . . . . . . . . . . . . . . . . 161 Classical and uncertain Hypergraph models with membership relations . . . . . . . . . . . . . 162 Classical and uncertain 𝑛-SuperHyperGraph models with membership relations . . . . . . . . 163 Overview of some extensions of fuzzy graphs . . . . . . . . . . . . . . . . . . . . . . . . . . 164 Overview of some extensions of fuzzy hypergraphs . . . . . . . . . . . . . . . . . . . . . . . 165 Compact comparison: fuzzy graph vs. fuzzy hypergraph vs. fuzzy 𝑛-superhypergraph. . . . . . 166 Compact comparison: Fuzzy Graph vs. Single-Valued Neutrosophic Graph (SVNG). . . . . . 171 A catalogue of uncertainty-set families (U-Sets) by the dimension 𝑘 of the degree-domain Dom(𝑀) ⊆ [0, 1] 𝑘 [739]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 5.9 A catalogue of uncertainty-graph families (Uncertain Graphs) by the dimension 𝑘 of the degreedomain Dom(𝑀) ⊆ [0, 1] 𝑘 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 5.10 A catalogue of uncertainty-hypergraph families (Uncertain HyperGraphs) by the dimension 𝑘 of the degree-domain Dom(𝑀) ⊆ [0, 1] 𝑘 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 5.11 A catalogue of uncertainty-superhypergraph families (Uncertain 𝑛-SuperHyperGraphs) by the dimension 𝑘 of the degree-domain Dom(𝑀) ⊆ [0, 1] 𝑘 . . . . . . . . . . . . . . . . . . . . . . 183 5.12 A concise overview of Functorial Graphs, Functorial HyperGraphs, and Functorial SuperHyperGraphs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 265

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Appendix (List of Tables) 6.1 6.2 6.3 Concise overview of molecular graph, molecular hypergraph, and molecular 𝑛-SuperHyperGraph viewpoints. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202 Overview of competition graphs, competition hypergraphs, and competition 𝑛-SuperHyperGraphs.204 Concise overview of Quantum Graphs, Quantum HyperGraphs, and Quantum 𝑛-SuperHyperGraphs.211 7.1 7.2 7.3 Compact comparison: 𝑛-SuperHyperGraph vs. (𝑚, 𝑛)-SuperHyperGraph. . . . . . . . . . . . 246 Compact comparison: (𝑚, 𝑛)-SuperHyperGraph vs. (ℎ, 𝑘)-ary (𝑚, 𝑛)-SuperHyperGraph. . . . 247 Compact comparison: (𝑚, 𝑛)-SuperHyperGraph vs. Fuzzy (𝑚, 𝑛)-SuperHyperGraph. . . . . . 249 8.1 8.2 Concise overview of Structure, Hyperstructure, 𝑛-SuperHyperstructure, and (𝑚, 𝑛)-SuperHyperStructure.254 Keyword-style comparison of classical, hyper-, and superhyper- viewpoints across common domains (Part 1). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255 Keyword-style comparison across additional domains (Part 2). . . . . . . . . . . . . . . . . . 256 Keyword-style comparison across uncertainty/set- and algebra-oriented domains (Part 3). . . . 257 8.3 8.4 * 266

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HyperGraph and SuperHyperGraph Theory with Applications

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