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: "structural tractability of enumerating csp solutions"
  Abstract: The problem of deciding whether CSP instances admit solutions has been deeply studied in the literature, and several structural tractability results have been derived so far. However, constraint satisfaction comes in practice as a computation problem where the focus is either on finding one solution, or on enumerating all solutions, possibly projected to some given set of output variables. The paper investigates the structural tractability of the problem of enumerating (possibly projected) solutions, where tractability means here computable with polynomial delay (WPD), since in general exponentially many solutions may be computed. A framework based on the notion of tree projection of hypergraphs is considered, which generalizes all structural decomposition methods that are based on decomposing a given instance into suitable tree-like groups of polynomial-time computable subproblems. Tractability results have been obtained both for classes of structures where output variables are part of their specification, and for classes of structures where computability WPD must be ensured for any possible set of output variables. By exhibiting dichotomies, these results are shown to be tight for classes of structures having bounded arity.

Connected through hyperedge HE-1 (induced by source paper "tree projections and constraint optimization problems fixed parameter tractability and parallel algorithms"):
  with members:
    - "constraint solving via fractional edge covers"
    - "greedy strategies and larger islands of tractability for conjunctive queries and constraint satisfaction problems"
    - "general and fractional hypertree decompositions hard and easy cases"
    - "aggregations over generalized hypertree decompositions"
    - "faq questions asked frequently"
    - "a quasi polynomial time partition oracle for graphs with an excluded minor"
    - "possibilistic constraint satisfaction problems or how to handle soft constraints"
    - "tree projections and structural decomposition methods minimality and game theoretic characterization"

Connected through hyperedge HE-2 (induced by source paper "answering conjunctive queries under updates"):
  with members:
    - "answering fo mod queries under updates on bounded degree databases"
    - "size bounds and query plans for relational joins"
    - "dynamic conjunctive queries"
    - "faster online matrix vector multiplication"
    - "unifying and strengthening hardness for dynamic problems via the online matrix vector multiplication conjecture"
    - "joins via geometric resolutions worst case and beyond"
    - "a trichotomy in the complexity of counting answers to conjunctive queries"
    - "structural tractability of counting of solutions to conjunctive queries"

Connected through hyperedge HE-3 (induced by source paper "structural tractability of counting of solutions to conjunctive queries"):
  with members:
    - "constraint solving via fractional edge covers"
    - "on the complexity of existential positive queries"
    - "the complexity of weighted counting for acyclic conjunctive queries"
    - "beyond hypertree width decomposition methods without decompositions"
    - "hypertree decompositions and tractable queries"

Connected through hyperedge HE-4 (induced by source paper "d flat declarative problem solving using tree decompositions and answer set programming"):
  with members:
    - "tractable optimization problems through hypergraph based structural restrictions"
    - "the language features and architecture of b prolog"
    - "the dlv system for knowledge representation and reasoning"
    - "hypertree decompositions and tractable queries"
    - "stable models and an alternative logic programming paradigm"

Connected through hyperedge HE-5 (induced by source paper "tree projections and structural decomposition methods the power of local consistency and larger islands of tractability"):
  with members:
    - "constraint solving via fractional edge covers"
    - "tractable hypergraph properties for constraint satisfaction and conjunctive queries"
    - "beyond hypertree width decomposition methods without decompositions"
    - "hypertree decompositions and tractable queries"

Connected through hyperedge HE-6 (induced by source paper "tree projections and structural decomposition methods minimality and game theoretic characterization"):
  with members:
    - "constraint solving via fractional edge covers"
    - "tractable hypergraph properties for constraint satisfaction and conjunctive queries"
    - "hypertree decompositions and tractable queries"

Connected through hyperedge HE-7 (induced by source paper "symmetry breaking with polynomial delay"):
  with members:
    - "practical graph isomorphism ii"

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.AI(Artificial Intelligence)