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: "data structure lower bounds for document indexing problems"
  Abstract: We study data structure problems related to document indexing and pattern matching queries and our main contribution is to show that the pointer machine model of computation can be extremely useful in proving high and unconditional lower bounds that cannot be obtained in any other known model of computation with the current techniques. Often our lower bounds match the known space-query time trade-off curve and in fact for all the problems considered, there is a very good and reasonable match between the our lower bounds and the known upper bounds, at least for some choice of input parameters. The problems that we consider are set intersection queries (both the reporting variant and the semi-group counting variant), indexing a set of documents for two-pattern queries, or forbiddenpattern queries, or queries with wild-cards, and indexing an input set of gapped-patterns (or two-patterns) to find those matching a document given at the query time. 1998 ACM Subject Classification F.2.2 Nonnumerical Algorithms and Problems

Connected through hyperedge HE-1 (induced by source paper "fast join project query evaluation using matrix multiplication"):
  with members:
    - "memory efficient group by aggregates over multi way joins"
    - "trade offs in static and dynamic evaluation of hierarchical queries"
    - "size bounds and query plans for relational joins"
    - "extracting and analyzing hidden graphs from relational databases"
    - "compressed representations of conjunctive query results"
    - "improved rectangular matrix multiplication using powers of the coppersmith winograd tensor"
    - "set containment join revisited"
    - "skew strikes back new developments in the theory of join algorithms"

Connected through hyperedge HE-2 (induced by source paper "on the hardness of set disjointness and set intersection with bounded universe"):
  with members:
    - "how hard is it to find honest witnesses"
    - "conditional lower bounds for space time tradeoffs"
    - "dynamic set intersection"
    - "popular conjectures imply strong lower bounds for dynamic problems"
    - "on hardness of jumbled indexing"
    - "higher lower bounds from the 3sum conjecture"
    - "approximate distance oracle with constant query time"
    - "exact weight subgraphs and the k sum conjecture"

Connected through hyperedge HE-3 (induced by source paper "lower bounds for text indexing with mismatches and differences"):
  with members:
    - "approximate nearest neighbor search in high dimensions"
    - "hardness of approximate nearest neighbor search"
    - "probabilistic polynomials and hamming nearest neighbors"

Connected through hyperedge HE-4 (induced by source paper "compressed representations of conjunctive query results"):
  with members:
    - "size bounds and query plans for relational joins"
    - "conditional lower bounds for space time tradeoffs"
    - "answering conjunctive queries under updates"
    - "extracting and analyzing hidden graphs from relational databases"
    - "aggregation and ordering in factorised databases"
    - "structural tractability of counting of solutions to conjunctive queries"
    - "skew strikes back new developments in the theory of join algorithms"
    - "fdb a query engine for factorised relational databases"

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.DS(Data Structures and Algorithms)