Event Based Web Service Description and Coordination

This paper proposes the concept of business events as the cornerstone to web service description and coordination. First, a web service architecture is introduced as the result of an event based analysis & design phase. Then, it is advocated how the event concept can be used for semantically rich web service description. A distinction is made between two web service interfaces: a non-transactional query interface and a transactional event notification interface. Furthermore, a web service composition model is proposed, based on event broadcasting and event preconditions, instead of traditional one-to-one method invocations. The composition model is presented in a static variant and in a version with dynamic subscription. Throughout the paper, it is shown how the event based approach fits entirely within the current standard SOAP/WSDL/UDDI web services stack.