Requirement Definition Taking a Flyer on DO-254

Abstract

Defining requirements that both capture the essential properties at a given hierarchical level and meet the appropriate needs of that hierarchical level is never any easy task. ISO 26262 has a fairly minimal coverage on how to achieve the hierarchical relations of hardware requirements and also the abstract way the standard has evolved over two versions adds some confusion to this subject. The DO-254 Design Assurance Guidance for Airborne Electronic Hardware conversely gives very good guidance on this topic, albeit that DO-254 is now 20 years old, does that really matter? There are techniques from more modern guidance that can augment the definition in DO-254 and support ISO 26262 hardware definition and implementation. In this paper we look at the strategy defined in DO-254 and combining this with more recent thinking on the subject to propose a method for assisting the ISO 26262 requirement definition activities. We also consider at what level ISO 26262 hardware parts should or should not be traceable to hardware safety requirements.