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: "constraint propagation in presence of arrays"
  Abstract: We describe the use of array expressions as constraints, which represents a consequent generalisation of the "element" constraint. Constraint propagation for array constraints is studied theoretically, and for a set of domain reduction rules the local consistency they enforce, arc-consistency, is proved. An efficient algorithm is described that encapsulates the rule set and so inherits the capability to enforce arc-consistency from the rules.

Connected through hyperedge HE-1 (induced by source paper "a combined approach for constraints over finite domains and arrays"):
  with members:
    - "efficient constraint propagation engines"

Connected through hyperedge HE-2 (induced by source paper "infinite qualitative simulations by means of constraint programming"):
  with members:
    - "relation variables in qualitative spatial reasoning"
    - "constraint based qualitative simulation"
    - "efficient methods for qualitative spatial reasoning"

Connected through hyperedge HE-3 (induced by source paper "relation variables in qualitative spatial reasoning"):
  with members:
    - "combining cardinal direction relations and relative orientation relations in qualitative spatial reasoning"
    - "the complexity of reasoning about spatial congruence"

Connected through hyperedge HE-4 (induced by source paper "constraint based qualitative simulation"):
  with members:
    - "relation variables in qualitative spatial reasoning"
    - "efficient methods for qualitative spatial reasoning"

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)