Event-Based Interaction Management for Composite E-Services in eFlow

The Web is rapidly becoming the platform through which many companies deliver e-services to businesses and individual customers. E-Services are typically delivered in their primitive forms, called basic services. However, today's business environment creates the opportunity for providing value-added, integrated services, delivered by composing existing e-services, possibly offered by different providers. In order to enable organizations to pursue this business opportunity we have developed eFlow, a model and architecture that support the specification, enactment, and management of composite e-services, modeled as processes that are enacted by a process engine. In this paper we focus on one of the most important and innovative aspects of eFlow: that of the integration between service composition and event management. In particular, we extend classic service composition model by allowing composite services to publish and receive events. This capability enables composite services to dynamically exchange data with other applications (in the form of event parameters), to synchronize service invocations with the occurrence of (external or internal) events, and to handle exceptions occurring during service execution. One of our main objectives has been that of defining a model that is easy to understand and easy to use. Indeed, all types of events are handled in the same fashion from the user perspective, and high-level constructs are provided to handle critical events such as those related to time management. Finally, we show how the proposed approach can be implemented by integrating existing technologies.