Research On The Approach To Web Services Composition And Its Application In EAM System

SOA(Service Oriented Architecture)is becoming a main trend of software development,getting more and more attention, it not only accomplishes enterprise application intergration interoperability between enterprise systems, but also can align IT systems with the business,enables IT Systems to quickly adapt to changing business needs. The key of SOA is “service”,it is convenient to construct loosely-coupled enterprise application system on demand through services reuse and quick composition. At present, there are a large number of services in the Internet, so how to compose these services with single function to accomplish the complex business attracts much concern of industry and academia.Service composition can be classified into two categories: automatic and semi-automatic composition, the major work and contributions for these two aspects are as follow:First, we proposed an automatic service compositon approach based on directed level graph. It first searches the Web Services repository according to service request to generate directed level graph; then generates a complete reduction graph; then searches optimal valid path, gets the optimal service composition sequence. The features of this approach include small search space, low time, space complexity, good user satisfaction. A set of experiments indicate that it can be applied for a large scale of Web Services repository with multiple inputs/outputs.Second, we proposed a semi-automatic QoS-aware service composition approach based on Markov Decesion Process. it models the process of web service selection as DTMDP(Discrete Time Markov Decesion Process), it divides the state space of the binding process,specifies the transition probability according to the QoS value, contains a web services composition framework with QoS management to get real-time QoS information, it takes account of invoking failure of Web service, the experimental results indicate this approach can improve the success rate of service composition and keep a steady success rate in dynamic environment, is an effective approach to service composition.Last, we proposed a framework of EAM prototype system based on Web Services, these approaches to web service composition are applied to the EAM system elementarily.