Programming languages for use in safety-related applications

Programmable electronic systems are being used in almost all application sectors to perform non-safety and increasingly to perform safety functions as well. Although software based solutions are usually superior to hardwired ones for reasons of e ciency and exibility, there is a certain reluctance of the certi cation authorities when it comes to licensing computer based systems which are classi ed as safety critical. Despite many attempts to overcome problems of software safety (IEC 61508, IEC 880, VDE 0801, IDS 00-55, RTCA/DO-178), up to now neither precise guidelines supporting the software development process are available, nor are there serious e orts being made to develop programming languages dedicated to the implementation of safety critical functions. To improve this unsatisfactory situation, i.e., to meet both economic and safety requirements, it is necessary to design appropriate language concepts with consequent regard to safety aspects. Accordingly, four subsets of a real time language suitable for the implementation of safety related systems are proposed, whose de nitions ful l the respective requirements of the four Safety Integrity Levels.