A novel layered method was proposed to solve the problem of Web services composition.In this method,services composition problem was formally transformed into the optimal matching problem of every layer,then optimal matching problem was modeled based on the hypergraph theory,and solved by computing the minimal transversals of the hypergraph.Meanwhile,two optimization algorithms were designed to discard some useless states at the intermediary steps of the composition algorithm.The effectiveness of the composition method was tested by a set of experiments,in addition,an example regarding the travel services composition was also given.The experimental results show that this method not only can automatically generate composition tree whose leaf nodes correspond to services composition solutions,but also has better performance on execution time and solution quality by adopting two proposed optimization algorithms.
为了增强传统Petri网的建模能力,将随机时间与库所关联,提出了SPPN(Stochastic Places Petri Net-随机库所Petri网),并基于SPPN分析了任务间的关系。对网上企业销售系统,采取从单个组织到组织合成的方法,应用SPPN和逻辑Petri网进行建模,并给出了逻辑工作流网模型的可达图的构造算法,分析了模型的正确性。
