human: Given a hyperedge-centered hypergraph: <hypergraph>, where the center hyperedge groups authors who co-authored the same paper.

Details of the hypergraph:
Center hyperedge (induced by source paper "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.

Includes members:
  Member "Security analysis of cryptographically controlled access to XML documents":
    also connected through other hyperedges:
      - Hyperedge HE-1 (induced by source paper "Deductive databases for computing certain and consistent answers from mediated data integration systems")
  Member "Extending Acyclicity Notions for Existential Rules (\emph{long version})":
    also connected through other hyperedges:
      (none)

Question: Please tell me which research area the co-authored paper (i.e., the source paper of the center hyperedge) belongs to. The 4 classes are: Computer science, Mathematics, Engineering, Economics, Psychology, Business. Directly output the class name.

gpt: Mathematics