Document Type



As the Web services paradigm becomes popular and more and more applications are created and deployed as Web services, the need for developing new solutions tackling the composition of Web services becomes manifest. However, emerging web service standards and existing methods are not sufficient for realizing the goal of flexible and dynamic composition of Web services, although some preliminary work has been conducted in the area of services composition. This situation has raised the interesting research points for creating and developing new approaches for the Web services composition. In this paper we separate the design and implementation phases of the composite services, and concentrate on the research of the way a composite service is constructed in terms of its constituent services. We call this way the composition logic of a composite service. We firstly propose well-defined notions “composition structures” to represent the joints among the constituent services and generate the reliable structure of a composite service, and then we provide a specification mechanism to clearly specify the internal dependencies of a composite service in terms of the notification and dataflow dependencies. Our solutions for planning and specifying the composition of Web services can effectively support the properties of modularity, interoperability, dynamic reconfigure-ability and fault-tolerance for a composite software system in the dynamic Web environments of business applications, which are a organic part of our framework for tackling the challenges of Web service discovery and composition on which we are working.