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: "class invariants concepts problems solutions"
  Abstract: Class invariants are both a core concept of object-oriented programming and the source of the two key open OO verification problems: furtive access (from callbacks) and reference leak. Existing approaches force on programmers an unacceptable annotation burden. This article explains invariants and solves both problems modularly through the O-rule, defining fundamental OO semantics, and the inhibition rule, using information hiding to remove harmful reference leaks. It also introduces the concept of "object tribe" as a basis for other possible approaches. #R##N#For all readers: this article is long because it includes a tutorial, covers many examples and dispels misconceptions. To understand the key ideas and results, however, the first two pages suffice. #R##N#For non-experts in verification: all concepts are explained; anyone with a basic understanding of object-oriented programming can understand the discussion. #R##N#For experts: the main limitation of this work is that it is a paper proposal (no soundness proof, no implementation). It addresses, however, the known problems with class invariants, solving such examples as linked lists and Observer, through a simple theory and without any of the following: ownership; separation logic; universe types; object wrapping and unwrapping; semantic collaboration, observer specifications; history invariants; "inc" and "coop" constructs; friendship construct; non-modular reasoning. More generally, it involves no new language construct and no new programmer annotations.

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.SE(Software Engineering)