Independent validation of software safety requirements for systems of systems

As one can only reason about the safety of software within the system context in which the software is executing, traditional independent validation and verification approaches which focus on the assurance of satisfaction of requirements by the delivered software are not sufficient in the assurance of software safety requirements. This paper presents an extension to an approach to assurance that relies on the use of a system reference model to capture an independent verification and validation team´s understanding of a system´s requirements. Here we describe how to apply the approach in conjunction with hazard analysis to evaluate the sufficiency of the software safety requirements early in the software development process. We explain this approach using examples of the safe hold requirements for a spacecraft system.