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: "virtualizing system and ordinary services in windows based os level virtual machines"
  Abstract: OS-level virtualization incurs smaller start-up and run-time overhead than HAL-based virtualization and thus forms an important building block for developing fault-tolerant and intrusion-tolerant applications. A complete implementation of OS-level virtualization on the Windows platform requires virtualization of Windows services, such as system services like the Remote Procedure Call Server Service (RPCSS), because they are essentially extensions of the kernel. As Windows system services work very differently from their counterparts on UNIX-style OS, i.e., daemons, and many of their implementation details are proprietary, virtualizing Windows system services turned out to be the most challenging technical barrier for OS-level virtualization for the Windows platform. In this paper, we describe a general technique to virtualize Windows services, and demonstrate its effectiveness by applying it to successfully virtualize a set of important Windows system services and ordinary services on different versions of Windows OS, including RPCSS, DcomLaunch, IIS service group, Tlntsvr, MySQL, Apache2.2, CiSvc, ImapiService, etc.

Connected through hyperedge HE-1 (induced by source paper "duplication of windows services"):
  with members:
    - "design and implementation of a network security management system"
    - "a study on altering postgresql from multi processes structure to multi threads structure"
    - "implementing rbac model in an operating system kernel"
    - "suspicious taint based access control for protecting os from network attacks"
    - "compatible and usable mandatory access control for good enough os security"

Connected through hyperedge HE-2 (induced by source paper "design and implementation of a network security management system"):
  with members:
    - "a study on altering postgresql from multi processes structure to multi threads structure"
    - "implementing rbac model in an operating system kernel"
    - "suspicious taint based access control for protecting os from network attacks"
    - "compatible and usable mandatory access control for good enough os security"

Connected through hyperedge HE-3 (induced by source paper "confining windows inter process communications for os level virtual machine"):
  with members:
    - "design and implementation of a network security management system"
    - "a study on altering postgresql from multi processes structure to multi threads structure"
    - "implementing rbac model in an operating system kernel"
    - "suspicious taint based access control for protecting os from network attacks"

Connected through hyperedge HE-4 (induced by source paper "suspicious taint based access control for protecting os from network attacks"):
  with members:
    - "design and implementation of a network security management system"
    - "a study on altering postgresql from multi processes structure to multi threads structure"
    - "implementing rbac model in an operating system kernel"
    - "compatible and usable mandatory access control for good enough os security"

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.OS(Operating Systems)