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: "left bit right for sparql join queries with optional patterns left outer joins"
  Abstract: SPARQL basic graph pattern (BGP) (a.k.a. SQL inner-join) query optimization is a well researched area. However, optimization of OPTIONAL pattern queries (a.k.a. SQL left-outer-joins) poses additional challenges, due to the restrictions on the reordering of left-outer-joins. The occurrence of such queries tends to be as high as 50% of the total queries (e.g., DBPedia query logs).   In this paper, we present Left Bit Right (LBR), a technique for well-designed nested BGP and OPTIONAL pattern queries. Through LBR, we propose a novel method to represent such queries using a graph of supernodes, which is used to aggressively prune the RDF triples, with the help of compressed indexes. We also propose novel optimization strategies -- first of a kind, to the best of our knowledge -- that combine together the characteristics of acyclicity of queries, minimality, and nullification, best-match operators. In this paper, we focus on OPTIONAL patterns without UNIONs or FILTERs, but we also show how UNIONs and FILTERs can be handled with our technique using a query rewrite. Our evaluation on RDF graphs of up to and over one billion triples, on a commodity laptop with 8 GB memory, shows that LBR can process well-designed low-selectivity complex queries up to 11 times faster compared to the state-of-the-art RDF column-stores as Virtuoso and MonetDB, and for highly selective queries, LBR is at par with them.

Connected through hyperedge HE-1 (induced by source paper "efficient handling of sparql optional for obda extended version"):
  with members:
    - "semantics and complexity of sparql"

Connected through hyperedge HE-2 (induced by source paper "piwd a plugin based framework for well designed sparql"):
  with members:
    - "on the statistical analysis of practical sparql queries"
    - "efficient approximation of well designed sparql queries"
    - "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-3 (induced by source paper "on joining graphs"):
  with members:
    - "the gremlin graph traversal machine and language invited talk"
    - "ldql a query language for the web of linked data extended version"
    - "community structure in large networks natural cluster sizes and the absence of large well defined clusters"
    - "semantics and complexity of sparql"

Connected through hyperedge HE-4 (induced by source paper "processing sparql queries over distributed rdf graphs"):
  with members:
    - "partout a distributed engine for efficient rdf processing"
    - "performance guarantees for distributed reachability queries"
    - "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)