A software fault tree key node metric

Analysis of software fault trees exposes failure events that can impact safety within safety-critical software product lines. This paper presents a software fault tree key node safety metric for measuring software safety within product lines. Fault tree structures impacting the metric’s composition are provided, and the mathematical basis for the metric is defined. The metric is applied to an embedded control system as well as to a series of experiments expected to either improve or degrade system safety. The effectiveness of the metric is analyzed, and lessons learned during the application of the metric are discussed.