Research On Modeling Web Services Composition Based On Workflow

Web service represents the latest request of distributed computation, it has solved the problem of interoperation and integration in isomerous applications. With the development and widely application of Web services, Web services composition technology has become the key problem of Web services study. Business Process Execution Language as the standard of the process definition, due to the complexity of business logic,using BEPL to describe the complex business process is error-prone, therefore, to ensure business processes run correctly and efficiently, we should adopt effective methods to modeling, analyze, verify BPEL process.In this paper, for BPEL features, based on synchronized Petri net theory and without changing the basic character of the synchronized Petri net, it introduces some concepts of colored Petri net, extends the synchronized Petri net in some terms and proposes a model SPN-NET, which is more suitable for modeling BPEL.This model is simple,compact and good intelligibility. Then the BPEL and SPN-NET model transformation rules and mutual transformation algorithm were given. To further simplify the model,it proposes an algorithm based on similar structure.The paper gives a verification of the soundness and performance analysis of this Web services composition model based on SPN-NET. In the verification of the soundness, it uses of the existing reduction rules and extends two rules to simplify and verify the soundness of BPEL process.Also, based on the general Petri net reachable graph, it gives a reachable graph analysis for this model.In the performance evaluation, combined with a Markov chain method, a performance evaluation method by using queuing theory combination with the method of equivalent simplification is given in detail.Finally, a system framework of modeling tool which is based on SPN-NET is designed.It combines with an open source software [fireworkflow] and gives a initial implementation of modeling tool on using SPN-NET. The dynamic description of the model is given.And then it completes several examples that structural BPEL process documents conversion to the SPN-NET, and gives the test results. At last, a single-step dynamic simulation for an example is given.This paper focuses on the research of modeling Web services composition based on workflow, putting forward a model SPN-NET,which is more suitable for modeling BEPL.Basically solved the main problems in modeling, it has a certain value for promoting the Web service composition based on workflow technology.