human: Given a node-centered hypergraph: <hypergraph>, where nodes represent authors and hyperedges represent groups of authors who co-authored the same paper.

Details of the hypergraph:
Center node: "Extending decidable existential rules by joining acyclicity and guardedness"
  Abstract: Existential rules, i.e. Datalog extended with existential quantifiers in rule heads, are currently studied under a variety of names such as Datalog+/-, ∀∃-rules, and tuple-generating dependencies. The renewed interest in this formalism is fuelled by a wealth of recently discovered language fragments for which query answering is decidable. This paper extends and consolidates two of the main approaches in this field - acyclicity and guardedness - by providing (1) complexity-preserving generalisations of weakly acyclic and weakly (frontier-) guarded rules, and (2) a novel formalism of glut-(frontier-) guarded rules that subsumes both. This builds on an insight that acyclicity can be used to extend any existential rule language while retaining decidability. Besides decidability, combined query complexities are established in all cases.

Connected through hyperedge HE-1 (induced by source paper "Security analysis of cryptographically controlled access to XML documents"):
  with members:
    - "Reconciling Two Views of Cryptography (The Computational Soundness of Formal Encryption)"
    - "Entropy based nearest neighbor search in high dimensions"
    - "Deductive databases for computing certain and consistent answers from mediated data integration systems"

Connected through hyperedge HE-2 (induced by source paper "Extending Acyclicity Notions for Existential Rules (\emph{long version})"):
  with members:
    (none)

Question: Please tell me which research area the center author belongs to. The 4 classes are: Computer science, Mathematics, Engineering, Economics, Psychology, Business. Directly output the class name.

gpt: Mathematics