human: Given a hyperedge-centered hypergraph: <hypergraph>, where the center hyperedge is induced by one source paper and its member nodes are the cited papers.

Details of the hypergraph:
Center hyperedge (induced by source paper "a study on altering postgresql from multi processes structure to multi threads structure"):
  Abstract: How to altering PostgreSQL database from multi-processes structure to multi-threads structure is a difficult problem. In the paper, we bring forward a comprehensive alteration scheme. Especially, put rational methods to account for three difficult points: semaphores, signal processing and global variables. At last, applied the scheme successfully to modify a famous open source DBMS.

Includes members:
  Member "design and implementation of a network security management system":
    also connected through other hyperedges:
      - Hyperedge HE-1 (induced by source paper "duplication of windows services")
  Member "implementing rbac model in an operating system kernel":
    also connected through other hyperedges:
      - Hyperedge HE-2 (induced by source paper "duplication of windows services")
  Member "suspicious taint based access control for protecting os from network attacks":
    also connected through other hyperedges:
      - Hyperedge HE-3 (induced by source paper "an instrumenting compiler for enforcing confidentiality in low level code")
  Member "compatible and usable mandatory access control for good enough os security":
    also connected through other hyperedges:
      - Hyperedge HE-4 (induced by source paper "duplication of windows services")

Question: Please tell me which class the source paper 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)