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: "logical step indexed logical relations"
  Abstract: Appel and McAllester's "step-indexed" logical relations have proven to be a simple and effective technique for reasoning about programs in languages with semantically interesting types, such as general recursive types and general reference types. However, proofs using step-indexed models typically involve tedious, error-prone, and proof-obscuring step-index arithmetic, so it is important to develop clean, high-level, equational proof principles that avoid mention of step indices. In this paper, we show how to reason about binary step-indexed logical relations in an abstract and elegant way. Specifically, we define a logic LSLR, which is inspired by Plotkin and Abadi's logic for parametricity, but also supports recursively defined relations by means of the modal "later" operator from Appel, Melli\`es, Richards, and Vouillon's "very modal model" paper. We encode in LSLR a logical relation for reasoning relationally about programs in call-by-value System F extended with general recursive types. Using this logical relation, we derive a set of useful rules with which we can prove contextual equivalence and approximation results without counting steps.

Connected through hyperedge HE-1 (induced by source paper "compositional non interference for fine grained concurrent programs"):
  with members:
    - "a dependently typed library for static information flow control in idris"
    - "verifying that a compiler preserves concurrent value dependent information flow security"
    - "types for information flow control labeling granularity and semantic models"

Connected through hyperedge HE-2 (induced by source paper "polymorphism and the free bicartesian closed category"):
  with members:
    - "impredicative encodings of higher inductive types"
    - "proof nets coends and the yoneda isomorphism"

Connected through hyperedge HE-3 (induced by source paper "relational reasoning for markov chains in a probabilistic guarded lambda calculus"):
  with members:
    - "proving uniformity and independence by self composition and coupling"
    - "the guarded lambda calculus programming and reasoning with guarded recursion for coinductive types"
    - "coupling proofs are probabilistic product programs"
    - "a relational logic for higher order programs"
    - "guarded dependent type theory with coinductive types"
    - "differentially private bayesian programming"
    - "relational reasoning via probabilistic coupling"
    - "a lambda calculus foundation for universal probabilistic programming"

Connected through hyperedge HE-4 (induced by source paper "lewis meets brouwer constructive strict implication"):
  with members:
    - "a light modality for recursion"
    - "guard your daggers and traces properties of guarded co recursion"
    - "guarded dependent type theory with coinductive types"
    - "programming and reasoning with guarded recursion for coinductive types"
    - "sequent calculus in the topos of trees"
    - "constructive modalities with provability smack"
    - "epistemic updates on algebras"
    - "first steps in synthetic guarded domain theory step indexing in the topos of trees"

Connected through hyperedge HE-5 (induced by source paper "on completeness and parametricity in the realizability semantics of system f"):
  with members:
    - "on completeness of reducibility candidates as a semantics of strong normalization"

Connected through hyperedge HE-6 (induced by source paper "a monadic framework for relational verification applied to information security program equivalence and optimizations"):
  with members:
    - "proof relevant logical relations for name generation"
    - "hypercollecting semantics and its application to static analysis of information flow"
    - "lightdp towards automating differential privacy proofs"
    - "language integrated provenance"
    - "higher order approximate relational refinement types for mechanism design and differential privacy"
    - "the foundational cryptography framework"
    - "abstract effects and proof relevant logical relations"
    - "quantitative information flow as safety and liveness hyperproperties"

Connected through hyperedge HE-7 (induced by source paper "a relational logic for higher order programs"):
  with members:
    - "formal verification of higher order probabilistic programs reasoning about approximation convergence bayesian inference and optimization"
    - "coupling proofs are probabilistic product programs"
    - "deductive verification with relational properties"
    - "higher order approximate relational refinement types for mechanism design and differential privacy"
    - "classical predicative logic enriched type theories"

Connected through hyperedge HE-8 (induced by source paper "logical relations for coherence of effect subtyping"):
  with members:
    - "an operational foundation for delimited continuations in the cps hierarchy"

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)