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: "attribute value reordering for efficient hybrid olap"
  Abstract: The normalization of a data cube is the process of choosing an ordering for the attribute values, and the chosen ordering.Our optimized hybrid OLAP storage mechanism was observed to be 44% more storage efficient than ROLAP and the gains due to normalization alone accounted for 45% of this increase in efficiency.

Connected through hyperedge HE-1 (induced by source paper "better bitmap performance with roaring bitmaps"):
  with members:
    - "simd compression and the intersection of sorted integers"
    - "compressed bitmap indexes beyond unions and intersections"
    - "decoding billions of integers per second through vectorization"
    - "reordering rows for better compression beyond the lexicographic order"
    - "sorting improves word aligned bitmap indexes"
    - "concise compressed n composable integer set"

Connected through hyperedge HE-2 (induced by source paper "reordering columns for smaller indexes"):
  with members:
    - "sorting improves word aligned bitmap indexes"
    - "teaching an old elephant new tricks"
    - "pruning attribute values from data cubes with diamond dicing"
    - "locality and bounding box quality of two dimensional space filling curves"
    - "a comparison of five probabilistic view size estimation techniques in olap"

Connected through hyperedge HE-3 (induced by source paper "difference huffman coding of multidimensional databases"):
  with members:
    - "difference sequence compression of multidimensional databases"
    - "on the scalability of multidimensional databases"
    - "multidimensional or relational how to organize an on line analytical processing database"

Connected through hyperedge HE-4 (induced by source paper "caching in multidimensional databases"):
  with members:
    - "difference sequence compression of multidimensional databases"
    - "on the scalability of multidimensional databases"

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)