Abstract: Single Web service just provides limited functionality, Web services composition has become an important research aspect in Web services application domain. This paper proposed an approach based on AND/OR graph to compose semantic Web services automatically. It adds the semantics to Web services and has a smaller search space limited to the service composition AND/OR graph and it finds the best composition graph in the service composition AND/OR graph to achieve the purpose of optimizing services composition. I}hc results of the extensive experiments show that this method improves both the successful and the efficiency ratio of Web services composition.

Key words: Semantic Web services, Services composition, AND/OR graph