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: "lean and full congruence formats for recursion"
  Abstract: In this paper I distinguish two (pre)congruence requirements for semantic equivalences and preorders on processes given as closed terms in a system description language with a recursion construct. A lean congruence preserves equivalence when replacing closed subexpressions of a process by equivalent alternatives. A full congruence moreover allows replacement within a recursive specification of subexpressions that may contain recursion variables bound outside of these subexpressions. #R##N#I establish that bisimilarity is a lean (pre)congruence for recursion for all languages with a structural operational semantics in the ntyft/ntyxt format. Additionally, it is a full congruence for the tyft/tyxt format.

Connected through hyperedge HE-1 (induced by source paper "failure trace semantics for a process algebra with time outs preliminary report"):
  with members:
    - "ensuring liveness properties of distributed systems open problems"
    - "a theory of encodings and expressiveness"
    - "the coarsest precongruences respecting safety and liveness properties"

Connected through hyperedge HE-2 (induced by source paper "ensuring liveness properties of distributed systems open problems"):
  with members:
    - "progress justness and fairness"
    - "reward testing equivalences for processes"
    - "justness a completeness criterion for capturing liveness properties"
    - "analysing mutual exclusion using process algebra with signals"
    - "structure preserving bisimilarity supporting an operational petri net semantics of ccsp"
    - "ccs it s not fair fair schedulers cannot be implemented in ccs like languages even under progress and certain fairness assumptions"
    - "progress fairness and justness in process algebra"
    - "a process algebra for wireless mesh networks"

Connected through hyperedge HE-3 (induced by source paper "reward testing equivalences for processes"):
  with members:
    - "ensuring liveness properties of distributed systems a research agenda"
    - "progress fairness and justness in process algebra"
    - "on the axiomatizability of impossible futures"
    - "the coarsest precongruences respecting safety and liveness properties"
    - "characterising testing preorders for finite probabilistic processes"

Connected through hyperedge HE-4 (induced by source paper "on the meaning of transition system specifications"):
  with members:
    - "a theory of encodings and expressiveness"

Connected through hyperedge HE-5 (induced by source paper "a theory of encodings and expressiveness"):
  with members:
    - "priorities without priorities representing preemption in psi calculi"
    - "on the expressiveness of intensional communication"
    - "expressiveness via intensionality and concurrency"
    - "branching bisimilarity with explicit divergence"

Connected through hyperedge HE-6 (induced by source paper "rooted divergence preserving branching bisimilarity is a congruence"):
  with members:
    - "sequential composition in the presence of intermediate termination extended abstract"
    - "on the executability of interactive computation"
    - "computation tree logic with deadlock detection"
    - "branching bisimilarity with explicit divergence"

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.LO(Logic in Computer Science)