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: "maximal sharing in the lambda calculus with letrec"
  Abstract: Increasing sharing in programs is desirable to compactify the code, and to avoid duplication of reduction work at run-time, thereby speeding up execution. We show how a maximal degree of sharing can be obtained for programs expressed as terms in the lambda calculus with letrec. We introduce a notion of 'maximal compactness' for λletrec-terms among all terms with the same infinite unfolding. Instead of defined purely syntactically, this notion is based on a graph semantics. λletrec-terms are interpreted as first-order term graphs so that unfolding equivalence between terms is preserved and reflected through bisimilarity of the term graph interpretations. Compactness of the term graphs can then be compared via functional bisimulation.   We describe practical and efficient methods for the following two problems: transforming a λletrec-term into a maximally compact form; and deciding whether two λletrec-terms are unfolding-equivalent. The transformation of a λletrec-terms L into maximally compact form L0 proceeds in three steps: (i) translate L into its term graph G = [[L]] ; (ii) compute the maximally shared form of G as its bisimulation collapse G0 ; (iii) read back a λletrec-term L0 from the term graph G0 with the property [[L0]] = G0. Then L0 represents a maximally shared term graph, and it has the same unfolding as L.   The procedure for deciding whether two given λletrec-terms L1 and L2 are unfolding-equivalent computes their term graph interpretations [[L1]] and [[L2]], and checks whether these are bisimilar.   For illustration, we also provide a readily usable implementation.

Connected through hyperedge HE-1 (induced by source paper "modeling terms by graphs with structure constraints two illustrations"):
  with members:
    - "unfolding semantics of the untyped λ calculus with letrec"
    - "proceedings 7th international workshop on computing with terms and graphs"
    - "term graph representations for cyclic lambda terms"

Connected through hyperedge HE-2 (induced by source paper "sharing equality is linear"):
  with members:
    - "proof nets and the linear substitution calculus"
    - "on the relative usefulness of fireballs"

Connected through hyperedge HE-3 (induced by source paper "leftmost outermost beta reduction is invariant indeed"):
  with members:
    - "on constructor rewrite systems and the lambda calculus"
    - "execution time of lambda terms via denotational semantics and intersection types"

Connected through hyperedge HE-4 (induced by source paper "on the relative usefulness of fireballs"):
  with members:
    - "on constructor rewrite systems and the lambda calculus"

Connected through hyperedge HE-5 (induced by source paper "nested term graphs work in progress"):
  with members:
    - "term graph representations for cyclic lambda terms"

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)