How to Improve Safety Critical Systems Standards

Abstract: An effective standard for safety critical software systems is one that should help both developers and assessors of such systems. For developers it should be clear what is required in order to conform to the standard, while for assessors it should be possible to determine objectively compliance to the standard. The existing set of standards do not pass this basic quality test. We provide a framework for improving such standards. We view a standard as a collection of requirements. For each requirement we first identify the process, product, or resource that is the primary focus. Next we consider the clarity of the requirement in respect of the ease with which it is possible to assess conformance to it. We describe guidelines for interpreting requirements to make this task more objective. The method is applied extensively to the IEC 1508 Safety Critical Standard.