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: "discovering the skyline of web databases"
  Abstract: Many web databases are "hidden" behind proprietary search interfaces that enforce the top-$k$ output constraint, i.e., each query returns at most $k$ of all matching tuples, preferentially selected and returned according to a proprietary ranking function. In this paper, we initiate research into the novel problem of skyline discovery over top-$k$ hidden web databases. Since skyline tuples provide critical insights into the database and include the top-ranked tuple for every possible ranking function following the monotonic order of attribute values, skyline discovery from a hidden web database can enable a wide variety of innovative third-party applications over one or multiple web databases. Our research in the paper shows that the critical factor affecting the cost of skyline discovery is the type of search interface controls provided by the website. As such, we develop efficient algorithms for three most popular types, i.e., one-ended range, free range and point predicates, and then combine them to support web databases that feature a mixture of these types. Rigorous theoretical analysis and extensive real-world online and offline experiments demonstrate the effectiveness of our proposed techniques and their superiority over baseline solutions.

Connected through hyperedge HE-1 (induced by source paper "on obtaining stable rankings"):
  with members:
    - "a nutritional label for rankings"
    - "qr2 a third party query reranking service over web databases"
    - "rrr rank regret representative"
    - "ranking with fairness constraints"
    - "query reranking as a service"
    - "crowdsourcing pareto optimal object finding by pairwise comparisons"
    - "optimal aggregation algorithms for middleware"

Connected through hyperedge HE-2 (induced by source paper "rrr rank regret representative"):
  with members:
    - "qr2 a third party query reranking service over web databases"
    - "efficient algorithms for k regret minimizing sets"
    - "query reranking as a service"
    - "crowdsourcing pareto optimal object finding by pairwise comparisons"
    - "on the expected complexity of random convex hulls"
    - "optimal aggregation algorithms for middleware"

Connected through hyperedge HE-3 (induced by source paper "qr2 a third party query reranking service over web databases"):
  with members:
    - "query reranking as a service"
    - "optimal algorithms for crawling a hidden database in the web"
    - "optimal aggregation algorithms for middleware"

Connected through hyperedge HE-4 (induced by source paper "designing fair ranking schemes"):
  with members:
    - "ranking with fairness constraints"
    - "runaway feedback loops in predictive policing"
    - "query reranking as a service"
    - "measuring fairness in ranked outputs"
    - "on the im possibility of fairness"
    - "fairness through awareness"

Connected through hyperedge HE-5 (induced by source paper "query reranking as a service"):
  with members:
    - "aggregate estimation over dynamic hidden web databases"
    - "optimal algorithms for crawling a hidden database in the web"
    - "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.DB(Databases)