ABSTRACT

This paper presents the current position of the York Distributed Ada Project. The project has developed an approach to the programming of loosely coupled distributed systems in Ada, this being based on a single Ada program consisting of virtual nodes which communicate by message passing. A prototype development environment has been produced to support this approach, and an example distributed embedded system has been built. Preliminary work has been undertaken on mechanisms to support the construction of fault-tolerant systems within the approach.

INTRODUCTION

The Ada programming language, together with an appropriate support environment, is well suited to the development of large software engineering applications. Many such projects involve programming embedded computer systems, which often include loosely coupled distributed processing resources — collections of processing elements which are connected by some communication system but which share no common memory. It is now a commonly accepted view (Wellingsl987) that the Ada language by itself does not provide adequate support for the programming of these systems. The York Distributed Ada (YDA) Project has addressed this problem and developed an approach which allows Ada programs to be constructed for execution on distributed systems. (The YDA project was originally funded through the UK's Alvey Software Engineering Directorate as part of the ASPECT(Hall1985) project. It is currently funded by the Admiralty Research Establishment.) The current position of the project is presented in this paper.