Constraints in Web Services Composition

The development of Web services provides a convenient way to achieve various services on web. Web services composition is the key techniques in its application. Composition of Web service is always in a complex and distributed environment so there are many potential problems such as deadlock. To avoid those problems, we first model Web services as finite state machine and discuss the properties of Web services. Then constraints in composition are discussed exactly. We deliver the process of composition into three parts according to the merging process: constraints before composition, constraints in composition and constraints after composition. According to different steps, constraints of Web services composition are analyzed. Based on the discussion, a modified model is given with the constraint considerate. Model with constraints makes composition of Web services safe and effective in complex environment.