Experience Report: Orthogonal Classification of Safety Critical Issues

Techniques to classify defects have been used for decades, providing relevant information on how to improve systems. Such techniques heavily rely on human experience and have been generalized to cover different types of systems at different maturity levels. However, their application to safety-critical systems development and operation phases neither is very common, or at least not spread publicly, nor disseminated in the industrial and academic worlds. This practical experience report presents the results and conclusions from applying a mature Orthogonal Defect Classification (ODC) to a large set of safety-critical issues. The work is based on the analysis of more than 240 real issues (defects) identified during all the lifecycle phases of 4 safety-critical systems in the aerospace and space domains. The outcomes reveal the challenges in properly classifying this specific type of issues with the broader ODC approach. The difficulties are identified and systematized and specific proposals for improvement are proposed.