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 re-cipient) that has declared some interest in it. This paradigm holds the promise of supporting a flexible and effective in-teraction among highly reconfigurable distributed software components. We have developed an object-oriented infrastructure, called JEDI (Java Event-based Distributed Infrastructure), to sup-port 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 sys-tem. Moreover, it provides an initial evaluation of our expe-riences in using an event-based architectural style