[SystemSafety] Difference between software reliability and astrology

[Dewi Daniels]

Derek,

No, it just means that FTA can't be used to predict a software failure
rate. In civil aviation, mitigation of random hardware failures is
performed by setting safety qualitative and/or quantitative requirements,
design errors are mitigated by implementation of a development assurance
process.

Yours,

Dewi Daniels | Director | Software Safety Limited

Telephone +44 7968 837742 | Email dewi.daniels at software-safety.com

Software Safety Limited is a company registered in England and Wales.
Company number: 9390590. Registered office: Fairfield, 30F Bratton Road,
West Ashton, Trowbridge, United Kingdom BA14 6AZ


On Thu, 22 Aug 2024 at 11:13, Derek M Jones <derek at knosof.co.uk> wrote:

> Mike,
>
> > Guidance from the FAA is the software included in any FTA analysis
> should be assigned a failure rate of zero. The rational being that software
> failure rates are in general cannot be reliably estimated and thus the
> dependence/reliance on DO178.
>
> Does this mean that it's not possible for anyone to report software
> as the cause of a particular failure?
>
> After all, if the failure rate is specified as zero, software can
> never be considered a cause of failure.
>
> A software failure rate of zero becomes a self fulfilling prophesy.
>
> --
> Derek M. Jones           Evidence-based software engineering
> blog:https://shape-of-code.com
>
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