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: "saturation algorithms for model checking pushdown systems"
  Abstract: Pushdown systems have, over the past 15 years, been popular with the software verification community. Their stack can be used to model the call stack of a first-order recursive program, with the control state holding valuations of the program’s global variables, and stack characters encoding the local variable valuations. As such the control flow of first-order recursive programs (such as C and Java programs) can be accurately modelled [29]. Pushdown systems have played a key role in the automata-theoretic approach to software model checking and considerable progress has been made in the implementation of scalable model checkers of pushdown systems. These tools (e.g. Bebop [3] and Moped [21, 39, 52, 50]) are an essential back-end components of high-profile model checkers such as SLAM [2]. A fundamental result for the model-checking of pushdown systems was established by Buchi in [12]. He showed that the set of stack contents reachable from the initial configuration of a pushdown system form a regular language and hence can be represented by a finite state automaton. The procedure provided by Buchi to compute this automaton from the pushdown system is exponential. In [15], Caucal gave the first polynomial time algorithm to solve this problem. This efficient computation is obtained by a saturation process where transitions are incrementally added to the finite automaton. This technique, which is the topic of this survey, was simplified and adapted to the model-checking setting by Bouajjani et al. in [7] and independently by Finkel et al. in [22]. The saturation technique allows global model checking of pushdown systems. For example, one may construct a regular representation of all configurations reachable from a given set of initial configurations, or, dually, the set of all configurations that may reach a given set of target configurations. As well as providing direct solutions to simple reachability properties (e.g. can an error state be reached from a designated initial configuration), the representations constructed by global analyses may be reused in a variety of settings. For example, once may perform multiple (and dynamic) queries on the set of reachable states without having to re-run the model checking routine. Additionally, these representations may be combined as part of a larger algorithm or proof. For example, Bouajjani et al. provided solutions to the model checking problem for the alternation free μ-calculus by combining the results obtained through multiple global reachability analyses [7]. In this survey, we present the saturation method under its different forms for reachability problems in Section 3. The saturation technique also generalises to the analysis of two-players games played over the configuration graph of a pushdown systems. This extension based on the work of Cachat [13] and Hague and Ong [28] is presented in Section 4. In Section 5, we review the various model-checking tools that

Connected through hyperedge HE-1 (induced by source paper "good for games omega pushdown automata"):
  with members:
    - "good for games automata from nondeterminism to alternation"

Connected through hyperedge HE-2 (induced by source paper "antichains for inclusion games"):
  with members:
    - "lazy automata techniques for ws1s"
    - "advanced automata minimization"

Connected through hyperedge HE-3 (induced by source paper "reachability analysis of first order definable pushdown systems"):
  with members:
    - "timed pushdown automata revisited"
    - "automata theory in nominal sets"
    - "reachability problem for weak multi pushdown automata"
    - "model checking of ordered multi pushdown automata"
    - "ltl with the freeze quantifier and register automata"
    - "alternating timed automata"

Connected through hyperedge HE-4 (induced by source paper "ordered tree pushdown systems"):
  with members:
    - "saturation of concurrent collapsible pushdown systems"
    - "model checking of ordered multi pushdown automata"
    - "strictness of the collapsible pushdown hierarchy"
    - "the safe lambda calculus"
    - "a finite semantics of simply typed lambda terms for infinite runs of automata"

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.FL(Formal Languages and Automata Theory)