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: "guarded second order logic spanning trees and network flows"
  Abstract: According to a theorem of Courcelle monadic second-order logic and guarded#N#second-order logic (where one can also quantify over sets of edges) have the#N#same expressive power over the class of all countable $k$-sparse hypergraphs.#N#In the first part of the present paper we extend this result to hypergraphs of#N#arbitrary cardinality. In the second part, we present a generalisation dealing#N#with methods to encode sets of vertices by single vertices.

Connected through hyperedge HE-1 (induced by source paper "the limits of efficiency for open and closed world query evaluation under guarded tgds"):
  with members:
    - "when is ontology mediated querying efficient"
    - "containment for rule based ontology mediated queries"
    - "semantic acyclicity under constraints"
    - "querying the guarded fragment"
    - "ontology based data access a study through disjunctive datalog csp and mmsnp"
    - "tractable hypergraph properties for constraint satisfaction and conjunctive queries"

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)