A calculation method for software safety integrity level

Abstract

In the functional safety standards (IEC 61508 and ISO/DIS 26262), development methods and quantitative analytical methods are defined for establishment of safety-related systems. However, only development methods are recommended to establish the software of safety-related systems. That is, the safety integrity level for software is determined only by the number of the development methods applied to practical safety-related system development. This is not reasonable to evaluate the safety integrity level, because various risk factors should be taken up. In this paper, we propose how to calculate the safety integrity level for software. Especially, we propose the calculation method based on the software reliability growth model that has long been used in the large-scale system development.