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: "abstracting abstract machines"
  Abstract: We describe a derivational approach to abstract interpretation that yields novel and transparently sound static analyses when applied to well-established abstract machines. To demonstrate the technique and support our claim, we transform the CEK machine of Felleisen and Friedman, a lazy variant of Krivine's machine, and the stack-inspecting CM machine of Clements and Felleisen into abstract interpretations of themselves. The resulting analyses bound temporal ordering of program events; predict return-flow and stack-inspection behavior; and approximate the flow and evaluation of by-need parameters. For all of these machines, we find that a series of well-known concrete machine refactorings, plus a technique we call store-allocated continuations, leads to machines that abstract into static analyses simply by bounding their stores. We demonstrate that the technique scales up uniformly to allow static analysis of realistic language features, including tail calls, conditionals, side effects, exceptions, first-class continuations, and even garbage collection.

Connected through hyperedge HE-1 (induced by source paper "skeletal semantics and their interpretations"):
  with members:
    - "coinductive big step semantics for concurrency"
    - "abstracting abstract machines a systematic approach to higher order program analysis"
    - "mechanized semantics for the clight subset of the c language"

Connected through hyperedge HE-2 (induced by source paper "size change termination as a contract"):
  with members:
    - "soft contract verification for higher order stateful programs"
    - "abstracting definitional interpreters functional pearl"
    - "soft contract verification"
    - "from safety to termination and back smt based verification for lazy languages"
    - "abstracting abstract machines a systematic approach to higher order program analysis"
    - "higher order symbolic execution via contracts"
    - "a dynamic approach to characterizing termination of general logic programs"

Connected through hyperedge HE-3 (induced by source paper "abstracting definitional interpreters functional pearl"):
  with members:
    - "pushdown control flow analysis for free"
    - "galois transformers and modular abstract interpreters reusable metatheory for program analysis"
    - "soft contract verification"
    - "pushdown flow analysis with abstract garbage collection"
    - "simulation of two way pushdown automata revisited"
    - "abstracting abstract control extended"
    - "introspective pushdown analysis of higher order programs"
    - "systematic abstraction of abstract machines"

Connected through hyperedge HE-4 (induced by source paper "soft contract verification for higher order stateful programs"):
  with members:
    - "pushdown control flow analysis for free"
    - "soft contract verification"
    - "dependent types for javascript"
    - "higher order symbolic execution via contracts"

Connected through hyperedge HE-5 (induced by source paper "pushdown control flow analysis for free"):
  with members:
    - "optimizing abstract abstract machines"
    - "abstracting abstract control extended"
    - "introspective pushdown analysis of higher order programs"
    - "cfa2 a context free approach to control flow analysis"
    - "pushdown control flow analysis of higher order programs"

Connected through hyperedge HE-6 (induced by source paper "automating abstract interpretation of abstract machines"):
  with members:
    - "higher order symbolic execution via contracts"

Connected through hyperedge HE-7 (induced by source paper "soft contract verification"):
  with members:
    - "abstracting abstract control extended"
    - "concrete semantics for pushdown analysis the essence of summarization"
    - "dependent types for javascript"
    - "systematic abstraction of abstract machines"
    - "higher order symbolic execution via contracts"

Connected through hyperedge HE-8 (induced by source paper "pruning pushdown exception flow analysis"):
  with members:
    - "sound and precise malware analysis for android via pushdown reachability and entry point saturation"
    - "anadroid malware analysis of android with user supplied predicates"
    - "introspective pushdown analysis of higher order programs"
    - "pushdown control flow analysis of higher order programs"

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)