Coordinated roles: Promoting re-usability of coordinated active objects using event notification protocols

Abstract

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.