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: "a process calculus for formally verifying blockchain consensus protocols"
  Abstract: Blockchains are becoming increasingly relevant in a variety of fields, such as finance, logistics, and real estate. The fundamental task of a blockchain system is to establish data consistency among distributed agents in an open network. Blockchain consensus protocols are central for performing this task. #R##N#Since consensus protocols play such a crucial role in blockchain technology, several projects are underway that apply formal methods to these protocols. One such project is carried out by a team of the Formal Methods Group at IOHK. This project, in which the author is involved, aims at a formally verified implementation of the Ouroboros family of consensus protocols, the backbone of the Cardano blockchain. The first outcome of our project is the $\natural$-calculus (pronounced "natural calculus"), a general-purpose process calculus that serves as our implementation language. The $\natural$-calculus is a domain-specific language embedded in a functional host language using higher-order abstract syntax. #R##N#This paper will be a ramble through the $\natural$-calculus. First we will look at its language and its operational semantics. The latter is unique in that it uses a stack of two labeled transition systems to treat phenomena like data transfer and the opening and closing of channel scope in a modular fashion. The presence of multiple transition systems calls for a generic treatment of derived concurrency concepts. We will see how such a treatment can be achieved by capturing notions like scope opening and silent transitions abstractly using axiomatically defined algebraic structures based on functors and monads.

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)