Research Of Reliable Web Service Composition Method Based On Redundancy

With the Web service technology's development, Web services and their composition are used widely in the domain of e-business, application integration and business flow, etc. However, many key problems in Web service composition are still need to be addressed. A very important one is how to guarantee the reliablity of Web service composition. At present, the research mainly focuses on introducing excepion handling mechanism, or enhancing the reliability of service composition by invoking redundancy services. But that the uncertainty of Web will affect web service composition is not taken into account adequately. The method to discovery redundancy services is not proposed too. In the base of existing achievements, we delve into the following key aspects: redundancy services discovering, reliable Web service composition, producing the plan of Web service composition, ect. The contributions of our work are as follows.Firstly, to discover redundancy services, the Web service discovery is divided into two stages. Related service to user's request is discovered using index table in the first stage. Based on the results of the first stage, satisfied Web service operations are matching exactly using the semantics of operations' parameter in the second stage. After the two stages, redundancy services with the same function are discovered, which serves for the composition of reliable Web service compostion.Secondly, N-version programming provides an effective way to improve the dependability of Web services composition. But if the number of web services with same function is enormous, it will cause the time of Web services composition to increase greatly. With this problem in mind, a method of proxy service is proposed. The proxy service can not only ensure the reliability of Web services composition, but also safeguard against the response time to be so long.Finally, the paper discusses how to build reliable Web service composition using proxy service in detail. Reliable service composition based on Web services composition flow graph is demonstrated especially. Experiments of redundancy Web services dicovery and reliable Web service composition verify the effect in the end.