Abstract
One of the most promising advantages of Web service technology is the possibility of creating value-added services by combining existing ones. For interactive services, sending and receiving an arbitrary number of messages may occur during a service process. It is important that the service composition is not only based on input/output interface, but also related to process behaviour. This paper deals with the problem of interactive Web service composition, ie, for a complex interactive composition schema, and how to discover and select concrete services to satisfy the requirements of users and service interaction. Firstly, a Web service is modelled as an open Petri net, with messages and inner process description, and the service interaction is achieved via asynchronous composition. Then, according to abstract composite service, concrete services are discovered by some rules. These rules include interface consistency, structural-characteristic preservation, which assures the correct interaction between services. With the help of Petri net language, the similarity degree of abstract and concrete services based on their interface and inner process is evaluated, which provides guides for service selection.