Standards interoperability: Applying software safety assurance standards to the evolution of legacy software

In this paper we treat software evolution from the perspective of standards interoperability. We address the issue of how to apply contemporary software safety assurance standards to legacy safety-critical systems, with the aim of re-certifying the legacy systems to the contemporary standards. We present a model to capture the relationships between pre- and post-modification software and standards, and a framework to provide guidance on how to achieve airworthiness certification for modified legacy software, whilst maximizing the use of software products from the previous development.