human: Given a hyperedge-centered hypergraph: <hypergraph>, where the center hyperedge is induced by one source paper and its member nodes are the cited papers.

Details of the hypergraph:
Center hyperedge (induced by source paper "piwd a plugin based framework for well designed sparql"):
  Abstract: In the real world datasets (e.g.,DBpedia query log), queries built on well-designed patterns containing only AND and OPT operators (for short, WDAO-patterns) account for a large proportion among all SPARQL queries. In this paper, we present a plugin-based framework for all SELECT queries built on WDAO-patterns, named PIWD. The framework is based on a parse tree called \emph{well-designed AND-OPT tree} (for short, WDAO-tree) whose leaves are basic graph patterns (BGP) and inner nodes are the OPT operators. We prove that for any WDAO-pattern, its parse tree can be equivalently transformed into a WDAO-tree. Based on the proposed framework, we can employ any query engine to evaluate BGP for evaluating queries built on WDAO-patterns in a convenient way. Theoretically, we can reduce the query evaluation of WDAO-patterns to subgraph homomorphism as well as BGP since the query evaluation of BGP is equivalent to subgraph homomorphism. Finally, our preliminary experiments on gStore and RDF-3X show that PIWD can answer all queries built on WDAO-patterns effectively and efficiently.

Includes members:
  Member "on the statistical analysis of practical sparql queries":
    also connected through other hyperedges:
      - Hyperedge HE-1 (induced by source paper "algorithms and analysis for the sparql constructs")
  Member "efficient approximation of well designed sparql queries":
    also connected through other hyperedges:
      - Hyperedge HE-2 (induced by source paper "on the statistical analysis of practical sparql queries")
  Member "left bit right for sparql join queries with optional patterns left outer joins":
    also connected through other hyperedges:
      - Hyperedge HE-3 (induced by source paper "efficient handling of sparql optional for obda extended version")
  Member "context free path queries on rdf graphs":
    also connected through other hyperedges:
      - Hyperedge HE-4 (induced by source paper "understanding data science lifecycle provenance via graph segmentation and summarization")
  Member "processing sparql queries over distributed rdf graphs":
    also connected through other hyperedges:
      - Hyperedge HE-5 (induced by source paper "adaptive low level storage of very large knowledge graphs")
  Member "on the satisfiability problem for sparql patterns":
    also connected through other hyperedges:
      - Hyperedge HE-6 (induced by source paper "path discovery by querying the federation of relational database and rdf graph")
  Member "efficient subgraph matching on billion node graphs":
    also connected through other hyperedges:
      - Hyperedge HE-7 (induced by source paper "fast detection of maximum common subgraph via deep q learning")
  Member "foundations of sparql query optimization":
    also connected through other hyperedges:
      - Hyperedge HE-8 (induced by source paper "towards an integrated graph algebra for graph pattern matching with gremlin extended version")

Question: Please tell me which class the source paper 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)