Exploiting an event-based infrastructure to develop complex distributed systems

The development of complex distributed systems demands for the creation of suitable architectural styles (or paradigms) and related run-time infrastructures. An emerging style that is receiving increasing attention is based on the notion of event. In an event-based architecture, distributed software components interact by generating and consuming events. The occurrence of an event in a component (called source) is asynchronously notified to any other component (called recipient) that has declared some interest in it. This paradigm holds the promise of supporting a flexible and effective interaction among highly reconfigurable distributed software components. We have developed an object-oriented infrastructure, called JEDI (Java Event-based Distributed Infrastructure), to support the development and operation of event-based systems. During the past year, JEDI has been used to implement a significant example of distributed system, namely, the OPSS workflow management system. The paper illustrates JEDI main features and how we have used it to implement the OPSS workflow management system. Moreover, it provides an initial evaluation of our experiences in using an event-based architectural style.