A Framework for the Server-Side Management of Conversations with Web Services

The emerging standards for the publication of Web Services are focused on the specification of the static interfaces of the operations to be invoked, or on the service composition. Few efforts have been made to specify the interaction between a Web Service and the individual consumer, although this aspect is essential to the successful service execution. In fact, while ``one-shot'' services may be invoked in a straightforward way, the invocation of services requiring complex interactions, where multiple messages are needed to complete the service, depends on the fact that the consumer respects the business logic of the Web Service. In this paper, we propose a framework for the server-side management of the interaction between a Web Service and its consumers. In our approach, the Web Service is in charge of assisting the consumer during the service invocation, by managing the interaction context and instructing the consumer about the operations that can be invoked and their actual parameters, at each step of the conversation. Our framework is based on the exchange of SOAP messages specifying the invocation of Java-based operations. Moreover, in order to support the interoperability with other software environments, the conversation flow specification is exported to a WSDL format that enables heterogeneous consumers to invoke the Web Service in a seamless way.