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: "introspective pushdown analysis of higher order programs"
  Abstract: In the static analysis of functional programs, pushdown flow analysis and abstract garbage collection skirt just inside the boundaries of soundness and decidability. Alone, each method reduces analysis times and boosts precision by orders of magnitude. This work illuminates and conquers the theoretical challenges that stand in the way of combining the power of these techniques. The challenge in marrying these techniques is not subtle: computing the reachable control states of a pushdown system relies on limiting access during transition to the top of the stack; abstract garbage collection, on the other hand, needs full access to the entire stack to compute a root set, just as concrete collection does. \emph{Introspective} pushdown systems resolve this conflict. Introspective pushdown systems provide enough access to the stack to allow abstract garbage collection, but they remain restricted enough to compute control-state reachability, thereby enabling the sound and precise product of pushdown analysis and abstract garbage collection. Experiments reveal synergistic interplay between the techniques, and the fusion demonstrates "better-than-both-worlds" precision.

Connected through hyperedge HE-1 (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"
    - "systematic abstraction of abstract machines"
    - "cfa2 a context free approach to control flow analysis"

Connected through hyperedge HE-2 (induced by source paper "pushdown control flow analysis for free"):
  with members:
    - "optimizing abstract abstract machines"
    - "abstracting abstract control extended"
    - "cfa2 a context free approach to control flow analysis"
    - "pushdown control flow analysis of higher order programs"
    - "abstracting abstract machines"

Connected through hyperedge HE-3 (induced by source paper "pushdown flow analysis with abstract garbage collection"):
  with members:
    - "deciding k cfa is complete for exptime"
    - "concrete semantics for pushdown analysis the essence of summarization"
    - "systematic abstraction of abstract machines"
    - "cfa2 a context free approach to control flow analysis"
    - "pushdown control flow analysis of higher order programs"

Connected through hyperedge HE-4 (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"
    - "pushdown control flow analysis of higher order programs"
    - "abstracting abstract machines"

Connected through hyperedge HE-5 (induced by source paper "abstracting abstract control extended"):
  with members:
    - "simulation of two way pushdown automata revisited"
    - "optimizing abstract abstract machines"
    - "systematic abstraction of abstract machines"
    - "cfa2 a context free approach to control flow analysis"
    - "pushdown control flow analysis of higher order programs"
    - "abstracting abstract machines"
    - "first order and temporal logics for nested words"

Connected through hyperedge HE-6 (induced by source paper "optimizing abstract abstract machines"):
  with members:
    - "automatic verification of erlang style concurrency"
    - "abstracting abstract machines a systematic approach to higher order program analysis"
    - "systematic abstraction of abstract machines"
    - "cfa2 a context free approach to control flow analysis"
    - "higher order symbolic execution via contracts"

Connected through hyperedge HE-7 (induced by source paper "concrete semantics for pushdown analysis the essence of summarization"):
  with members:
    - "optimizing abstract abstract machines"
    - "cfa2 a context free approach to control flow analysis"
    - "pushdown control flow analysis of higher order programs"
    - "abstracting abstract machines"
    - "first order and temporal logics for nested words"

Connected through hyperedge HE-8 (induced by source paper "sound and precise malware analysis for android via pushdown reachability and entry point saturation"):
  with members:
    - "quire lightweight provenance for smart phone operating systems"
    - "abstracting abstract machines"

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)