【摘要】 摘现有的Web服务容错侧重于通过扩展Web服务标准来提供容错能力.由于Web服务标准体系本身不断发展变化,并且标准之间的兼容性问题依然存在,使得这些研究成果的可实施性较弱.文章提出一种基于移动Agent的复合Web服务容错模型——MAFTM模型,从系统层次而非标准层次来解决复合 Web服务的容错问题.首先说明基于移动Agent的工作流与复合Web服务的关系.在此基础上,给出MAFTM模型,包括故障类型、复制机制、“exactly once”语义和一致性算法,并证明MAFTM模型的正确性.更多还原

【Abstract】 Fault tolerant is one of the fundamental issues in Web service reliability. Current researches focus on achieving fault tolerant Web service through extending Web service related standards. Because these standards are evolving and have some compatibility problems, approaches used in existing works cannot provide a practical way to implement a fault tolerant mechanism for Web service. This paper presents a mobile agent based fault tolerant model, called MAFTM, for composite Web service at the system level. Since mobile agent based workflow is suitable for distributed Web service composition, the authors use mobile agents to provide fault tolerant capability for composite Web service. The MAFTM model concentrates on crash failures and communication link failures. Based on their previous work of the totally ordered multicast for mobile agents, the authors design a replication mechanism that introduces a group of replicated mobile agents to maintain a group of replicated instances for one composite Web service. To assure “exactly once” semantics in the execution of replicated instances, the authors propose a consensus algorithm. This algorithm can be used to guarantee that, in each step of the composite Web service, all replicated mobile agents agree on only one committed atomic Web service. Also, they prove properties of the MAFTM model including agreement, validity, integration and termination.更多还原