Web services composition is a complex and error-prone process, but there are no effective verification mechanisms among the existing composition specifications. Based on the semantics of web services ontology language OWL-S, a formal description and modeling method using Hierarchical Colored Petri nets(HCPN) for web services composition processes is proposed. In the method, the control and data flow information of web services composition process model which is described by the OWL-S can be transformed into HCPN model, with the ease of simulation and verification. On the other hand, the state space explosion problem can be transfered into the memory limit of computer which is not a serious problem now. With the help of CPN-Tools, the established HCPN model can be simulated dynamicly, the dynamic behaviors of the model can be obtained, and the correctness and effectiveness of web services composition can be verified. The method can be used to analyze and verify complex systems. An instance of hospital services is given to illustrate the modeling and analysis of the service composition process with HCPN.
A comparative illustration of AI planning-based web services composition