A practical use of the Ada Rendez-Vous paradigm in distributed systems

Abstract

This is the result of a work done to generalize the Ada Rendez-Vous mechanism, when developing an application distributed among several processes and machines, while keeping a clear separation between the objects semantics and the physical communication issues. The proposed mechanism is based upon a Client-Server architecture, coping with several types of Server (Mono and Multi Client), and requiring only any validated Ada-83 compiler and a task-to-task communication layer.

We describe how such an architecture can be developped using Object-Oriented Design methods, and how its components can afterwards be distributed on different machines in a transparent manner. We show that its implementation depends upon nothing but the Ada Server Specification. We have therefore developed a tool (using Alex and Ayacc utilities to create a simple Ada grammar parser and a generator) capable of automatically building the additionnal bricks needed by the mechanism. The implementation-dependent features dealing with physical communication are kept encapsulated in a generic layer, the only piece to modify should another communication layer be chosen.