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: "ultimate approximations in nonmonotonic knowledge representation systems"
  Abstract: We study fixpoints of operators on lattices. To this end we introduce the notion of an approximation of an operator. We order approximations by means of a precision ordering. We show that each lattice operator O has a unique most precise or ultimate approximation. We demonstrate that fixpoints of this ultimate approximation provide useful insights into fixpoints of the operator O. #R##N#We apply our theory to logic programming and introduce the ultimate Kripke-Kleene, well-founded and stable semantics. We show that the ultimate Kripke-Kleene and well-founded semantics are more precise then their standard counterparts We argue that ultimate semantics for logic programming have attractive epistemological properties and that, while in general they are computationally more complex than the standard semantics, for many classes of theories, their complexity is no worse.

Connected through hyperedge HE-1 (induced by source paper "from fuzzy to annotated semantic web languages"):
  with members:
    - "description logics with fuzzy concrete domains"
    - "on the undecidability of fuzzy description logics with gcis with lukasiewicz t norm"
    - "a general framework for representing reasoning and querying with annotated semantic web data"
    - "on the failure of the finite model property in some fuzzy description logics"
    - "fuzzy ontology representation using owl 2"
    - "reasoning with very expressive fuzzy description logics"
    - "epistemic foundation of stable model semantics"
    - "reasoning within fuzzy description logics"

Connected through hyperedge HE-2 (induced by source paper "logic programs with propositional connectives and aggregates"):
  with members:
    - "propositional theories are strongly equivalent to logic programs"
    - "answer sets for logic programs with arbitrary abstract constraint atoms"
    - "well founded and stable semantics of logic programs with aggregates"
    - "weight constraints as nested expressions"
    - "strong equivalence made easy nested expressions and weight constraints"
    - "des a challenge problem for nonmonotonic reasoning systems"
    - "stable models and an alternative logic programming paradigm"

Connected through hyperedge HE-3 (induced by source paper "epistemic foundation of stable model semantics"):
  with members:
    - "uniform semantic treatment of default and autoepistemic logics"

Connected through hyperedge HE-4 (induced by source paper "logic programs with monotone cardinality atoms"):
  with members:
    - "tight logic programs"
    - "local search techniques for propositional logic extended with cardinality constraints"
    - "propositional satisfiability in answer set programming"

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)