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: "on the statistical analysis of practical sparql queries"
  Abstract: In this paper, we analyze some basic features of SPARQL queries coming from our practical world in a statistical way. These features include three statistic features such as the occurrence frequency of triple patterns, fragments, well-designed patterns and four semantic features such as monotonicity, non-monotonicity, weak monotonicity (old solutions are still served as parts of new solutions when some new triples are added) and satisfiability. All these features contribute to characterize SPARQL queries in different dimensions. We hope that this statistical analysis would provide some useful observation for researchers and engineers who are interested in what practical SPARQL queries look like, so that they could develop some practical heuristics for processing SPARQL queries and build SPARQL query processing engines and benchmarks. Besides, they can narrow the scope of their problems by avoiding those cases that do possibly not happen in our practical world.

Connected through hyperedge HE-1 (induced by source paper "algorithms and analysis for the sparql constructs"):
  with members:
    - "foundations of sparql query optimization"
    - "semantics and complexity of sparql"

Connected through hyperedge HE-2 (induced by source paper "an analytical study of large sparql query logs"):
  with members:
    - "gmark schema driven generation of graphs and queries"
    - "enumeration problems for regular path queries"
    - "old techniques for new join algorithms a case study in rdf processing"
    - "flexible caching in trie joins"
    - "a trichotomy for regular simple path queries on graphs"
    - "an empirical study of real world sparql queries"
    - "semantics and complexity of sparql"
    - "hypertree decompositions and tractable queries"

Connected through hyperedge HE-3 (induced by source paper "piwd a plugin based framework for well designed sparql"):
  with members:
    - "efficient approximation of well designed sparql queries"
    - "left bit right for sparql join queries with optional patterns left outer joins"
    - "context free path queries on rdf graphs"
    - "processing sparql queries over distributed rdf graphs"
    - "on the satisfiability problem for sparql patterns"
    - "efficient subgraph matching on billion node graphs"
    - "foundations of sparql query optimization"
    - "semantics and complexity of sparql"

Connected through hyperedge HE-4 (induced by source paper "efficient approximation of well designed sparql queries"):
  with members:
    - "relative expressive power of navigational querying on graphs"
    - "on the satisfiability problem for sparql patterns"
    - "foundations of sparql query optimization"
    - "semantics and complexity of sparql"

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)