Optimize The Selection Of Research, Qos-based Web Service Composition

Web Service is a new and distributed application, which has been recognized by the academic area and the industry because of the advantages-loosely coupled, standardization and high degree of integration it posses. The problem of granularity has limited its application, and it is necessary to composite several Services together to provide more powerful functions. However, with the development of Web Services, there will appear inevitably a lot of Web Services which have same or similar functions but differences in QoS (Quality of Service). These Web Services can be combined into numerous programs, in which the selection of Web Service based on global QoS constrains plays an important role. As a result, how to provide a better mechanism, through which we can select a high-quality composited program, is a hot topic currently.This paper proposes a framework of Web Service Composition on the basis of Semantic Web Services. The framework expands the WSDL (Web Services Description Language) and the standard information of UDDI (Universal Description, Discovery and Integration). According to the parameter-level domain ontology and the extended semantic information of Web Service, this paper establishes an abstract model of Service.Based on the Composite Service QoS model, this paper designs a Web Services combiner, which transforms the combinatorial optimization problem of Web Service into the problem of accessible path with constraints in directed dependent graph. It adopts a certain strategy to optimize service composition and selects an optimal composite plan with global QoS. The results of experiment indicate the feasibility of the strategy of Web Services combiner.