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: "requirements for digital preservation systems a bottom up approach"
  Abstract: The field of digital preservation is being defined by a set of standards developed top-down, starting with an abstract reference model (OAIS) and gradually adding more specific detail. Systems claiming conformance to these standards are entering production use. Work is underway to certify that systems conform to requirements derived from OAIS. #R##N#We complement these requirements derived top-down by presenting an alternate, bottom-up view of the field. The fundamental goal of these systems is to ensure that the information they contain remains accessible for the long term. We develop a parallel set of requirements based on observations of how existing systems handle this task, and on an analysis of the threats to achieving the goal. On this basis we suggest disclosures that systems should provide as to how they satisfy their goals.

Connected through hyperedge HE-1 (induced by source paper "when should i make preservation copies of myself"):
  with members:
    - "resurrecting my revolution using social link neighborhood in bringing context to the disappearing web"
    - "the mellon fedora project digital library architecture meets xml and web services"
    - "http mailbox asynchronous restful communication"
    - "analysis of graphs for digital preservation suitability"
    - "from random graph to small world by wandering"
    - "object re use exchange a resource centric approach"
    - "adore a modular standards based digital object repository"

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)