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: "as time goes by constraint handling rules a survey of chr research from 1998 to 2007"
  Abstract: Constraint Handling Rules (CHR) is a high-level programming language based on multi-headed multiset rewrite rules. Originally designed for writing user-defined constraint solvers, it is now recognized as an elegant general purpose language. CHR-related research has surged during the decade following the previous survey by Fruehwirth. Covering more than 180 publications, this new survey provides an overview of recent results in a wide range of research areas, from semantics and analysis to systems, extensions and applications.

Connected through hyperedge HE-1 (induced by source paper "on proving confluence modulo equivalence for constraint handling rules"):
  with members:
    - "diagrammatic confluence for constraint handling rules"
    - "a complete and terminating execution model for constraint handling rules"

Connected through hyperedge HE-2 (induced by source paper "constraint handling rules with binders patterns and generic quantification"):
  with members:
    - "complete and easy bidirectional typechecking for higher rank polymorphism"

Connected through hyperedge HE-3 (induced by source paper "on termination confluence and consistent chr based type inference"):
  with members:
    - "smchr satisfiability modulo constraint handling rules"
    - "diagrammatic confluence for constraint handling rules"
    - "co inductive semantics for constraint handling rules"

Connected through hyperedge HE-4 (induced by source paper "a complete and terminating execution model for constraint handling rules"):
  with members:
    - "logical algorithms meets chr a meta complexity result for constraint handling rules with rule priorities"

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.PL(Programming Languages)