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: "combinatorial batch codes a lower bound and optimal constructions"
  Abstract: Batch codes, introduced by Ishai, Kushilevitz, Ostrovsky and Sahai in [1], are methods for solving the following data storage problem: n data items are to be stored in m servers in such a way that any k of the n items can be retrieved by reading at most t items from each server, and that the total number of items stored in m servers is N . A Combinatorial batch code (CBC) is a batch code where each data item is stored without change, i.e., each stored data item is a copy of one of the n data items. One of the basic yet challenging problems is to find optimal CBCs, i.e., CBCs for which total storage (N) is minimal for given values of n, m, k, and t. In [2], Paterson, Stinson and Wei exclusively studied CBCs and gave constructions of some optimal CBCs. In this article, we give a lower bound on the total storage (N) for CBCs. We give explicit construction of optimal CBCs for a range of values of n. For a different range of values of n, we give explicit construction of optimal and almost optimal CBCs. Our results partly settle an open problem of [2].

Connected through hyperedge HE-1 (induced by source paper "constructions of batch codes via finite geometry"):
  with members:
    - "bounds on the length of functional pir and batch codes"
    - "nearly optimal constructions of pir and batch codes"
    - "on private information retrieval array codes"
    - "lower bound on the redundancy of pir codes"
    - "pir array codes with optimal pir rate"
    - "pir with low storage overhead coding instead of replication"
    - "achieving arbitrary locality and availability in binary codes"
    - "locality and availability in distributed storage"

Connected through hyperedge HE-2 (induced by source paper "batch and pir codes and their connections to locally repairable codes"):
  with members:
    - "on private information retrieval array codes"
    - "lower bound on the redundancy of pir codes"
    - "pir array codes with optimal pir rate"
    - "cooperative local repair in distributed storage"
    - "pir with low storage overhead coding instead of replication"
    - "private information retrieval for coded storage"
    - "bounds for batch codes with restricted query size"
    - "applications of polymatroid theory to distributed storage systems"

Connected through hyperedge HE-3 (induced by source paper "nearly optimal constructions of pir and batch codes"):
  with members:
    - "lengthening and extending binary private information retrieval codes"
    - "locality via partially lifted codes"
    - "lower bound on the redundancy of pir codes"
    - "pir with low storage overhead coding instead of replication"
    - "bounds for batch codes with restricted query size"
    - "locality and availability in distributed storage"
    - "linear batch codes"
    - "a family of optimal locally recoverable codes"

Connected through hyperedge HE-4 (induced by source paper "explicit constructions and bounds for batch codes with restricted size of reconstruction sets"):
  with members:
    - "batch and pir codes and their connections to locally repairable codes"
    - "pir with low storage overhead coding instead of replication"
    - "achieving arbitrary locality and availability in binary codes"
    - "bounds for batch codes with restricted query size"
    - "linear batch codes"
    - "batch codes through dense graphs without short cycles"

Connected through hyperedge HE-5 (induced by source paper "multiset combinatorial batch codes"):
  with members:
    - "bounds and constructions of codes with multiple localities"
    - "fractional repetition and erasure batch codes"
    - "locality and availability in distributed storage"
    - "optimal combinatorial batch codes based on block designs"
    - "on an extremal hypergraph problem related to combinatorial batch codes"

Connected through hyperedge HE-6 (induced by source paper "batch codes from hamming and reed m uller codes"):
  with members:
    - "batch and pir codes and their connections to locally repairable codes"
    - "explicit constructions and bounds for batch codes with restricted size of reconstruction sets"
    - "binary linear locally repairable codes"
    - "optimal combinatorial batch codes based on block designs"
    - "a survey on network codes for distributed storage"

Connected through hyperedge HE-7 (induced by source paper "bounds for batch codes with restricted query size"):
  with members:
    - "cooperative local repair in distributed storage"
    - "pir with low storage overhead coding instead of replication"
    - "repair locality with multiple erasure tolerance"
    - "locality and availability in distributed storage"
    - "linear batch codes"
    - "codes with locality for two erasures"
    - "bounds on locally recoverable codes with multiple recovering sets"
    - "batch codes through dense graphs without short cycles"

Connected through hyperedge HE-8 (induced by source paper "derandomized construction of combinatorial batch codes"):
  with members:
    - "optimal combinatorial batch codes based on block designs"
    - "on an extremal hypergraph problem related to combinatorial batch codes"

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.DM(Discrete Mathematics)