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: "expressive path queries on graph with data"
  Abstract: Graph data models have recently become popular owing to their applications,#N#e.g., in social networks and the semantic web. Typical navigational query#N#languages over graph databases - such as Conjunctive Regular Path Queries#N#(CRPQs) - cannot express relevant properties of the interaction between the#N#underlying data and the topology. Two languages have been recently proposed to#N#overcome this problem: walk logic (WL) and regular expressions with memory#N#(REM). In this paper, we begin by investigating fundamental properties of WL#N#and REM, i.e., complexity of evaluation problems and expressive power. We first#N#show that the data complexity of WL is nonelementary, which rules out its#N#practicality. On the other hand, while REM has low data complexity, we point#N#out that many natural data/topology properties of graphs expressible in WL#N#cannot be expressed in REM. To this end, we propose register logic, an#N#extension of REM, which we show to be able to express many natural graph#N#properties expressible in WL, while at the same time preserving the#N#elementariness of data complexity of REMs. It is also incomparable to WL in#N#terms of expressive power.

Connected through hyperedge HE-1 (induced by source paper "modular path queries with arithmetic"):
  with members:
    - "querying best paths in graph databases"
    - "g core a core for future graph query languages"
    - "reachability in two dimensional vector addition systems with states is pspace complete"
    - "on the freeze quantifier in constraint ltl decidability and complexity"

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)