Standards Interoperability: Application of Contemporary Software Assurance Standards to the Evolution of Legacy Software

This thesis addresses 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. The application of RTCA DO-178B ‘Software Considerations in Airborne Systems and Equipment Certification’ to modified legacy software is the primary focus of this thesis. We present a model to capture the relationships between pre- and post-modification software and standards. The proposed formal model is then applied to the requirements for RTCA DO-178B and MIL-STD-498 as representative examples of contemporary and legacy software standards. The results provide guidance on how to achieve airworthiness certification for modified legacy software, whilst maximizing the use of software products from the previous development.