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Web服务的自包含、自描述和模块化的特性使之迅速受到工业界和学术界的极大关注,其中,服务组合是研究的热点和难点.然而Web服务的海量性、服务描述的异构性以及服务的动态变化性等因素决定了Web服务组合的困难性.本文提出了一种能够求出满足用户请求的所有组合方案的Web服务组合算法-双向算法,且算法的时间复杂度控制在多项式级别.通过预处理,该算法首先建立了输入参数与Web服务之间的关联关系,然后根据用户输入通过前向搜索,找出所有可能参与组合的服务,并建立了他们之间的可达关系,最后根据用户期望的输出,结合前向搜索得到的服务及可达关系,通过后向搜索得到所有的组合方案.
The self-contained, self-describing and modularized nature of Web services make it a rapid concern in industry and academia, of which service composition is a hot and difficult issue.However, the massiveness of Web services and the heterogeneity of service description As well as the dynamic changes of services and other factors determine the difficulty of Web service composition.This paper proposes a bidirectional algorithm that can be used to find out all the combinations of programs to meet user requests - and the algorithm’s time complexity control Polynomial level.Through preprocessing, the algorithm first establishes the relationship between input parameters and Web services, and then forward search according to user input to find out all the services that may participate in the combination, and establish a reachable Finally, based on the output expected by the user, combined with the service obtained by the forward search and the reachability relationship, all combination solutions are obtained through backward search.