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: "the adore federation architecture"
  Abstract: This paper describes the aDORe repository federation architecture, an outcome of the aDORe research and development effort by the Digital Library Research & Prototyping Team of the Los Alamos National Laboratory (LANL). The goal of the aDORe federation architecture is to facilitate a uniform manner for client applications to discover and access content objects available in a group of distributed repositories.  This is achieved by means of a 3-Tier architecture. Tier-3 provides client applications with a single point of access to all content available in the federation, irrespective of the actual location of that content in federated repositories.  In order to realize this, the architecture requires all federated repositories to implement the same, minimal set of machine interfaces to make their content accessible. These repository interfaces constitute Tier-1 of the architecture.  Moreover, the architecture requires the introduction of a middle Tier, Tier-2, consisting of two shared infrastructure components that keep the books on content objects, repositories, and repository interfaces in the federation.  These shared infrastructure components minimally expose one machine interface each. In order to respond to client requests, the federation’s single point of access interacts with these interfaces as well as with the interfaces exposed by the content repositories.

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.DL(Digital Libraries)