Safe Ada Executive: An executive for Ada safety critical applications

Abstract

This paper presents theSAE project(Safe Ada Executive) which deals with theD0-178 Bcertification for safety critical systems which use COTS (Commercial Off The Shelves) software components such as theAda Run Time System. Traditionally safety critical systems avoid parallelism or rely on cyclic dispatcher to achieve determinism. At the opposite this project shows that it is possible to use thepreemptive schedulerof the Ada Run Time System for safety critical systems. The proposed model of the Safe Ada Executive is designed to support a predictible subset of the Ada tasking. This real time executive allows to support applications developped with theRMA(Rate Monotonic Analysis) methods and an appropriate coding style. We point out this approach which allows to separate applications from the real time executive and to minimize the certification costs. Anyhow, the SAE project, based on the Ada83 revision of the language, has a stronger support with the Ada95 revision.