ABSTRACT
IEC 61508 Part 3 covers the development of software. Sections 4.1-4.8 summarise the main requirements. However, the following points should be noted first.
Whereas the reliability prediction of hardware failures, as addressed in Section 3.3.3 of the last chapter, implies a failure rate to be anticipated, the application of qualitative measures DOES NOT infer a failure rate for the systematic failures. All that can be reasonably claimed is that, given the state of the art, we believe the measures specified are appropriate for the integrity level in question and that therefore the systematic failures will probably be similar to and not exceed the hardware failure rate of that SIL.
