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A Practical Analytical Approach to Increase Confidence in Software Safety Arguments

Complex interdependencies among a large and growing number of elements in computer-based critical systems have made the safety analysis process more burdensome in terms of costs and tend to limit the capabilities of current safety analysis approaches to address system hazards. Therefore, the critical systems lifecycle—primarily software-intensive systems—demands new approaches for conducting the safety analysis process while staying within reasonable cost limits and maintaining the quality of the results. This paper proposes a practical analytical approach for increasing the confidence in software safety arguments in safety cases through the elaboration and assessment of counterevidence that emerges from software failure modes due to robustness issues. A case study is presented in which the proposed approach is applied to a computer-based distributed critical system. Additionally, practical results from the application of this approach to real safety-critical systems are also presented. The proposed approach proved to be useful during safety analysis processes, mainly in independent safety analysis projects, as it improves assessment coverage with low impact on workload and costs.