Dynamic Composition of Web Service Based on Coordination Model

To deal with Web service dynamicity and changes of application constraints in open distributed environment, a coordination model for dynamic service composition is presented. Based on the separation of concerns, there are three different categories of entities in a Web service-based application: Web service, role and coordinator. The Web service is only responsible for performing pure functional service, and carrying Out the task assigned by the role; the role is an abstraction for certain properties and functionalities, responsible for binding Web service according to constraints, and actively coordinating Web service to achieve coordination requirements; the coordinator is responsible for the coordination among roles by imposing coordination policies and binding constraints. The logic separation of Web services, roles, and coordinators in the model, decouples the dependencies between the coordinators and Web services. Thus, the model shields the coordinator layer from the dynamicity of Web services. Finally, a vehicle navigation application including traffic control Web services, GPS Web services and a navigator is illustrated how the model can be used to achieve the interaction adaptation by means of dynamic composition of Web service.