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1.
We present a randomized self-stabilizing leader election protocol and a randomized self-stabilizing token circulation protocol under an arbitrary scheduler on anonymous and unidirectional rings of any size. These protocols are space optimal. We also give a formal and complete proof of these protocols. To this end, we develop a complete model for probabilistic self-stabilizing distributed systems which clearly separates the non deterministic behavior of the scheduler from the randomized behavior of the protocol. This framework includes all the necessary tools for proving the self- stabilization of a randomized distributed system: definition of a probabilistic space and definition of the self-stabilization of a randomized protocol. We also propose a new technique of scheduler management through a self-stabilizing protocol composition (cross-over composition). Roughly speaking, we force all computations to have a fairness property under any scheduler, even under an unfair one. This work was done while Maria Gradinariu was working at LRI, Univ. Paris-Sud, CNRS.  相似文献
2.
A flexible way of building modular communication stacks relies on the use of protocol composition. This paper describes a protocol composition framework that simplifies the task of deriving the worst-case response time of a protocol composition from the protocol implementation. In order to derive the worst-case response time of a protocol composition, one needs to capture its event-graph: the event-graph consists of the set of all events processed by each component and the relation between those events. The framework, called RT-Appia, takes a pragmatic approach: instead of requiring the use of domain specific code analysis tools, or dedicated compilers, it simply requires protocol programmers to make explicit which events are processed and produced by each layer, and how these events are related. An interesting aspect of the approach is that the same data structures that are used to simplify the task of computing the worst-case response time of the protocol composition are also used to optimize the performance and to debug the resulting implementation.
Luís RodriguesEmail:
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3.
Summary. The complexity of designing protocols has led to compositional techniques for designing and verifying protocols. We propose a technique based on the notion of parallel composition of protocols. We view a composite protocol as an interleaved execution of the component protocols subject to a set of constraints. Using the constraints as building blocks, we define several constraint-based structures with each structure combining the properties of the component protocols in a different way. For instance, the component protocols of a multifunction protocol can be structured so that the composite protocol performs all the individual functions concurrently or performs only one of them depending on the order of initiation of the component protocols. We provide inference rules to infer safety and liveness properties of the composite protocol. Some properties are derived from those of the component protocols while others are derived from the structuring mechanism (the set of constraints) used to combine the component protocols. Received: October 1996 / Accepted: August 1998  相似文献
4.
李扬  怀进鹏  郭慧鹏  杜宗霞 《软件学报》2007,18(12):2967-2979
随着Internet上Web服务数量的不断增长,这些服务能够互联形成一个应用层的逻辑网络--服务层叠网(service overlay network,简称SON).基于SON,通过服务的组合提供增值服务,是满足用户动态、多变的功能及非功能需求的一种有效的方法.但是,已有基于SON的QoS感知的服务组合研究主要是面向服务间具有简单交互行为的应用领域,难以支持电子商务等具有复杂业务协作特征的应用场景.为此,通过使用业务协议刻画服务间的组合关系,从而构建更具普适性的SON;建立主动服务层叠网(active service overlay network,简称ASON)以实现可编程的服务层叠网,支持按需的服务组合;提出了一个基于主动服务层叠网的分层服务组合框架(hierachical service composition framework based on service overlay networks,简称HOSS),通过将业务协议(而不是消息)作为需求描述的基本单元,提升软件开发效率,并将服务组合需求映射为SON的动态用户视图以实现按需的组合.  相似文献
5.
A methodology is presented for the construction of communication protocols which perform several distinct functions simultaneously. The construction of such a multi-function protocol consists of three steps: (1) the development of component protocols for the different functions, (2) the integration of component protocols into a merged protocol, and (3) the specification of operational relationship among the component protocols. The conditions required for the resulting merged protocol to retain the safety properties, such as freedom from unspecified receptions, freedom from deadlocks, and boundedness, of the component protocols are discussed. The methodology is simple and facilitates the reuse of existing protocols. Two examples are given to illustrate its usage: a full-duplex data transfer protocol and another data transfer protocol with pipelining and flow control. Huai-An Lin received the B.S.E.E. degree from National Taiwan University, Taiwan, in 1977, and the M.S. and Ph.D. degrees in computer and information science from the Ohio State University, Columbus, Ohio, in 1981 and 1983, respectively. From 1983 to 1985, he was with the Gould Research Center at Rolling Meadows, Illinois. Since 1985, he has been an Assistant Professor of Electrical Engineering at University of Washington, Seattle, Washington. His research interests include computer communication networks, distributed systems, and software engineering. Dr. Lin is a member of the Institute of Electrical and Electronics Engineers and the Association for Computing Machinery.This research was partially supported by the Graduate School Research Fund of University of Washington  相似文献
6.
Overlay networks create new networking services using nodes that communicate using pre-existing networks. They are often optimized for specific applications and targeted at niche vertical domains, but lack interoperability with which their functionalities can be shared. Mosaic is a declarative platform for constructing new overlay networks from multiple existing overlays, each possessing a subset of the desired new network’s characteristics.This paper focuses on the design and implementation of Mosaic: composition and deployment of control and/or data plane functions of different overlay networks, dynamic compositions of overlay networks to meet changing application needs and network conditions, and seamless support for legacy applications. Mosaic overlays are specified using Mozlog, a new declarative language for expressing overlay properties independently from their particular implementation or underlying network.Mosaic is validated experimentally using compositions specified in Mozlog in order to create new overlay networks with compositions of their functions: the i3 indirection overlay that supports mobility, the resilient overlay network (RON) overlay for robust routing, and the Chord distributed hash table for scalable lookups. Mosaic uses runtime composition to simultaneously deliver application-aware mobility, NAT traversal and reliability. We further demonstrate Mosaic’s dynamic composition capabilities by Chord switching its underlay from IP to RON at runtime.Mosaic’s benefits are obtained at a low performance cost, as demonstrated by measurements on both a local cluster environment and the PlanetLab global testbed.  相似文献
7.
Kaman协议是移动Ad Hoc网络安全认证机制,然而,协议设计者未对该协议的安全性作严格的形式化分析。协议复合逻辑PCL是验证协议安全属性的形式化方法,PCL逻辑能够简化协议安全分析过程。本文在协议复合逻辑PCL中描述Kaman协议并分析Kaman协议的安全属性,证明Kaman协议能够实现其安全目标。  相似文献
8.
How to compose existing web services automatically and to guarantee the correctness of the design (e.g. temporal constraints specified by temporal logic LTL, CTL or CTL*) is an important and challenging problem in web services. Most existing approaches use the process in conventional software development of design, verification, analysis and correction to guarantee the correctness of composite services, which makes the composition process both complex and time-consuming. In this paper, we focus on the synthesis problem of composite service; that is, for a given set of services and correctness constraint specified by CTL or CTL* formula, a composite service is automatically constructed which guarantees that the correctness is ensured. We prove that the synthesis problem for CTL and CTL* are complete for EXPTIME and 2EXPTIME, respectively. Moreover, for the case of synthesis failure, we discuss the problem of how to disable outputs of environment (i.e. users or services) reasonably to make synthesis successful, which are also proved complete for EXPTIME and 2EXPTIME for CTL and CTL*, respectively.  相似文献
9.
10.
针对基于Web的业务流程建模问题,将业务流程的参与者抽象为角色,采用基于角色间交互的协议对业务流程进行建模,构造抽象的业务流程模板,提出一个业务协议组合代数,构造一组协议组合算子,即顺序、并发、选择和迭代,并证明该代数的一些相关性质,分析协议的相似性,从而为替换协议提供理论依据。  相似文献
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