Nowadays, the need for developing more and more complex applications with distributed capabilities has promoted the development
of coordination models. The goal of these models is to express the synchronized interaction among the different components
of a distributed application. Whilst the Concurrent Object Oriented Programming (COOP) paradigm has revealed special adaptation
to the modeling of distributed applications, the integration of this paradigm with current coordination models results in
a reduction of the potential re-usability of classes that negates the capital benefit of object orientation. The main contributions
of this paper are twofold. Firstly, the Event Notification Protocols, a mechanism that permits the transparent monitoring
of active objects, are presented. Secondly, Coordinated Roles, a general-purpose coordination model based on the event notification
protocols is proposed. Coordinated Roles is integrated with the COOP paradigm in such a way that the reduction of re-usability
is avoided. In addition, it provides flexibility, composability, polymorphism, distribution, and dynamic change of coordination
patterns.
This work is supported by CICYT under contract TIC 98-1049-C02-02 and Junta de Extremadura under contract IPR98A041.