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: "indexing the sphere with the hierarchical triangular mesh"
  Abstract: We describe a method to subdivide the surface of a sphere into spherical triangles of similar, but not identical, shapes and sizes. The Hierarchical Triangular Mesh (HTM) is a quad-tree that is particularly good at supporting searches at different resolutions, from arc seconds to hemispheres. The subdivision scheme is universal, providing the basis for addressing and for fast lookups. The HTM provides the basis for an efficient geospatial indexing scheme in relational databases where the data have an inherent location on either the celestial sphere or the Earth. The HTM index is superior to cartographical methods using coordinates with singularities at the poles. We also describe a way to specify surface regions that efficiently represent spherical query areas. This article presents the algorithms used to identify the HTM triangles covering such regions.

Connected through hyperedge HE-1 (induced by source paper "efficient classification of billions of points into complex geographic regions using hierarchical triangular mesh"):
  with members:
    - "a multi terabyte relational database for geo tagged social network data"

Connected through hyperedge HE-2 (induced by source paper "a multi terabyte relational database for geo tagged social network data"):
  with members:
    - "spatial indexing of large multidimensional databases"
    - "skyquery an implementation of a parallel probabilistic join engine for cross identification of multiple astronomical databases"
    - "array requirements for scientific applications and an implementation for microsoft sql server"
    - "batch is back casjobs serving multi tb data on the web"

Connected through hyperedge HE-3 (induced by source paper "the zones algorithm for finding points near a point or cross matching spatial datasets"):
  with members:
    - "when database systems meet the grid"
    - "there goes the neighborhood relational algebra for spatial data search"

Connected through hyperedge HE-4 (induced by source paper "using table valued functions in sql server 2005 to implement a spatial data library"):
  with members:
    - "there goes the neighborhood relational algebra for spatial data search"

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)