Modelling remote concurrency with Ada.Case study of symmetric non-deterministic rendez-vous.

Related material available on the Quasar Websitehttp://quasar.cnam.fr/files/concurrency_papers.htmlSubmitted to 12th Int Conf on Reliable Software Technologie Geneva 2007National audienceWhen developing concurrent software, a proper engineering practice is to choose a good level of abstraction for expressing concurrency control. Ideally, this level should provide platform-independent abstractions but, as the platform concurrency behaviour cannot be ignored, this abstraction level must also be able to cope with it and exhibit the influence of different possible behaviours. We state that the Ada language provides such a convenient abstraction level and thus may be used as a domain-specific language for concurrency description and evaluation, including distributed concurrency. For demonstrating it, we present two cooperative algorithms based on remote procedure calls which, although simply stated, contain actual concurrency complexity and difficulties. They allow a distributed symmetric non-deterministic rendez-vous. One relies on a common server and the second is fully distributed. Both realize a symmetric rendez-vous using an asymmetric RPC modelled by Ada rendez-vous. Using these case studies, we show that Ada concurrency features provide the adequate abstraction level both for describing and evaluating concurrency and for carrying out design decisions