human: Given a node-centered hypergraph: <hypergraph>, where nodes represent papers and hyperedges represent sets of papers co-cited by a source paper.

Details of the hypergraph:
Center node: "semantic acyclicity under constraints"
  Abstract: A conjunctive query (CQ) is semantically acyclic if it is equivalent to an acyclic one. Semantic acyclicity has been studied in the constraint-free case, and deciding whether a query enjoys this property is NP-complete. However, in case the database is subject to constraints such as tuple-generating dependencies (tgds) that can express, e.g., inclusion dependencies, or equality-generating dependencies (egds) that capture, e.g., functional dependencies, a CQ may turn out to be semantically acyclic under the constraints while not semantically acyclic in general. This opens avenues to new query optimization techniques. In this paper we initiate and develop the theory of semantic acyclicity under constraints. More precisely, we study the following natural problem: Given a CQ and a set of constraints, is the query semantically acyclic under the constraints, or, in other words, is the query equivalent to an acyclic one over all those databases that satisfy the set of constraints? We show that, contrary to what one might expect, decidability of CQ containment is a necessary but not sufficient condition for the decidability of semantic acyclicity. In particular, we show that semantic acyclicity is undecidable in the presence of full tgds (i.e., Datalog rules). In view of this fact, we focus on the main classes of tgds for which CQ containment is decidable, and do not capture the class of full tgds, namely guarded, non-recursive and sticky tgds. For these classes we show that semantic acyclicity is decidable, and its complexity coincides with the complexity of CQ containment. In the case of egds, we show that for keys over unary and binary predicates semantic acyclicity is decidable (NP-complete). We finally consider the problem of evaluating a semantically acyclic query over a database that satisfies a set of constraints; for guarded tgds and functional dependencies this problem is tractable.

Connected through hyperedge HE-1 (induced by source paper "when is ontology mediated querying efficient"):
  with members:
    - "the complexity of ontology based data access with owl 2 ql and bounded treewidth queries"
    - "ontology mediated queries combined complexity and succinctness of rewritings via circuit complexity"
    - "ontology based data access a study through disjunctive datalog csp and mmsnp"
    - "on the complexity of existential positive queries"
    - "the dl lite family and relations"

Connected through hyperedge HE-2 (induced by source paper "the limits of efficiency for open and closed world query evaluation under guarded tgds"):
  with members:
    - "when is ontology mediated querying efficient"
    - "containment for rule based ontology mediated queries"
    - "querying the guarded fragment"
    - "ontology based data access a study through disjunctive datalog csp and mmsnp"
    - "guarded second order logic spanning trees and network flows"
    - "tractable hypergraph properties for constraint satisfaction and conjunctive queries"

Connected through hyperedge HE-3 (induced by source paper "a more general theory of static approximations for conjunctive queries"):
  with members:
    - "constraint solving via fractional edge covers"
    - "general and fractional hypertree decompositions hard and easy cases"
    - "decidability results for the boundedness problem"
    - "querying the guarded fragment"
    - "beyond hypertree width decomposition methods without decompositions"
    - "hypertree decompositions and tractable queries"

Connected through hyperedge HE-4 (induced by source paper "all instances restricted chase termination"):
  with members:
    - "a single approach to decide chase termination on linear existential rules"
    - "acyclicity notions for existential rules and their application to query answering in ontologies"
    - "anatomy of the chase"
    - "on chase termination beyond stratification"

Connected through hyperedge HE-5 (induced by source paper "definability and interpolation within decidable fixpoint logics"):
  with members:
    - "decidability results for the boundedness problem"
    - "querying the guarded fragment"

Question: Please tell me which class the center node belongs to. The 40 classes are: cs.NA(Numerical Analysis), cs.MM(Multimedia), cs.LO(Logic in Computer Science), cs.CY(Computers and Society), cs.CR(Cryptography and Security), cs.DC(Distributed, Parallel, and Cluster Computing), cs.HC(Human-Computer Interaction), cs.CE(Computational Engineering, Finance, and Science), cs.NI(Networking and Internet Architecture), cs.CC(Computational Complexity), cs.AI(Artificial Intelligence), cs.MA(Multiagent Systems), cs.GL(General Literature), cs.NE(Neural and Evolutionary Computing), cs.SC(Symbolic Computation), cs.AR(Hardware Architecture), cs.CV(Computer Vision and Pattern Recognition), cs.GR(Graphics), cs.ET(Emerging Technologies), cs.SY(Systems and Control), cs.CG(Computational Geometry), cs.OH(Other Computer Science), cs.PL(Programming Languages), cs.SE(Software Engineering), cs.LG(Machine Learning), cs.SD(Sound), cs.SI(Social and Information Networks), cs.RO(Robotics), cs.IT(Information Theory), cs.PF(Performance), cs.CL(Computation and Language), cs.IR(Information Retrieval), cs.MS(Mathematical Software), cs.FL(Formal Languages and Automata Theory), cs.DS(Data Structures and Algorithms), cs.OS(Operating Systems), cs.GT(Computer Science and Game Theory), cs.DB(Databases), cs.DL(Digital Libraries), cs.DM(Discrete Mathematics). Directly output the class name.

gpt: cs.DB(Databases)