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: "characterization of search engine caches"
  Abstract: Search engines provide cached copies of indexed content so users will have something to "click on" if the remote resource is temporarily or permanently unavailable. Depending on their proprietary caching strategies, search engines will purge their indexes and caches of resources that exceed a threshold of unavailability. Although search engine caches are provided only as an aid to the interactive user, we are interested in building reliable preservation services from the aggregate of these limited caching services. But first, we must understand the contents of search engine caches. In this paper, we have examined the cached contents of Ask, Google, MSN and Yahoo to profile such things as overlap between index and cache, size, MIME type and "staleness" of the cached resources. We also examined the overlap of the various caches with the holdings of the Internet Archive.

Connected through hyperedge HE-1 (induced by source paper "evaluating sliding and sticky target policies by measuring temporal drift in acyclic walks through a web archive"):
  with members:
    - "access patterns for robots and humans in web archives"
    - "profiling web archive coverage for top level domain and content language"
    - "evaluating the sitestory transactional web archive with the apachebench tool"
    - "how much of the web is archived"
    - "an http based versioning mechanism for linked data"
    - "memento time travel for the web"

Connected through hyperedge HE-2 (induced by source paper "arclink optimization techniques to build and retrieve the temporal web graph"):
  with members:
    - "access patterns for robots and humans in web archives"
    - "how much of the web is archived"
    - "is this a good title"

Connected through hyperedge HE-3 (induced by source paper "how much of the web is archived"):
  with members:
    - "an http based versioning mechanism for linked data"
    - "memento time travel for the web"

Connected through hyperedge HE-4 (induced by source paper "investigating the change of web pages titles over time"):
  with members:
    - "evaluating personal archiving strategies for internet based information"

Connected through hyperedge HE-5 (induced by source paper "evaluating methods to rediscover missing web pages from the web infrastructure"):
  with members:
    - "evaluating personal archiving strategies for internet based information"

Connected through hyperedge HE-6 (induced by source paper "everyone is a curator human assisted preservation for ore aggregations"):
  with members:
    - "object re use exchange a resource centric approach"

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)