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 structure of collaborative tagging systems"
  Abstract: Collaborative tagging describes the process by which many users add metadata in the form of keywords to shared content. Recently, collaborative tagging has grown in popularity on the web, on sites that allow users to tag bookmarks, photographs and other content. In this paper we analyze the structure of collaborative tagging systems as well as their dynamical aspects. Specifically, we discovered regularities in user activity, tag frequencies, kinds of tags used, bursts of popularity in bookmarking and a remarkable stability in the relative proportions of tags within a given url. We also present a dynamical model of collaborative tagging that predicts these stable patterns and relates them to imitation and shared knowledge.

Connected through hyperedge HE-1 (induced by source paper "top k product design based on collaborative tagging data"):
  with members:
    - "optimal aggregation algorithms for middleware"

Connected through hyperedge HE-2 (induced by source paper "a methodology for internal web ethics"):
  with members:
    - "the web economy goods users models and policies"
    - "being space and time in the web"
    - "semantic similarity in a taxonomy an information based measure and its application to problems of ambiguity in natural language"

Connected through hyperedge HE-3 (induced by source paper "analyzing tag distributions in folksonomies for resource classification"):
  with members:
    - "empirical analysis of predictive algorithms for collaborative filtering"

Connected through hyperedge HE-4 (induced by source paper "cluster analysis for a scale free folksodriven structure network"):
  with members:
    - "folksodriven structure network"
    - "folks in folksonomies social link prediction from shared metadata"
    - "ontology temporal evolution for multi entity bayesian networks under exogenous and endogenous semantic updating"
    - "folksonomy as a complex network"

Connected through hyperedge HE-5 (induced by source paper "folks in folksonomies social link prediction from shared metadata"):
  with members:
    - "the stength of weak cooperation a case study on flickr"
    - "social browsing on flickr"

Connected through hyperedge HE-6 (induced by source paper "treelicious a system for semantically navigating tagged web pages"):
  with members:
    - "collaborative thesaurus tagging the wikipedia way"

Connected through hyperedge HE-7 (induced by source paper "collective dynamics of social annotation"):
  with members:
    - "semantic analysis of tag similarity measures in collaborative tagging systems"
    - "vocabulary growth in collaborative tagging systems"
    - "systematic topology analysis and generation using degree correlations"
    - "collaborative tagging and semiotic dynamics"

Connected through hyperedge HE-8 (induced by source paper "socialscope enabling information discovery on social content sites"):
  with members:
    - "optimal aggregation algorithms for middleware"

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)