Re: [SystemSafety] Fault, Failure and Reliability Again (short)

From: Nick Tudor < >
Date: Tue, 3 Mar 2015 10:03:32 +0000

Hi Peter

Tis I

The fault with the logic in your blog is that the design of your system fails to meet the specification; this I hope is obvious. The software is therefore as you suggest 100% reliable. Or not if it hits the one fault.

The term reliability in systems has been hijacked to mean something else in software and is reinterpreted very badly to say that it therefore has a reliability of one in a thousand ( or whatever). Clearly if the software never encounters 20 it never gives an incorrect answer.

Reliability models for software is still not recognised in DO-178C and this means it has not been recognised for over 25 years.

On Tuesday, 3 March 2015, Peter Bernard Ladkin <ladkin_at_xxxxxx wrote:

> I had some private discussion with someone here who claims software cannot
> fail. I first heard this
> trope a quarter century ago, and I am informed indirectly by another
> colleague that it is still rife
> in certain critical-engineering areas. I address it this morning in a blog
> post at
> Prof. Peter Bernard Ladkin, Faculty of Technology, University of
> Bielefeld, 33594 Bielefeld, Germany
> Je suis Charlie
> Tel+msg +49 (0)521 880 7319
> _______________________________________________
> The System Safety Mailing List
> systemsafety_at_xxxxxx >

Nick Tudor
Tudor Associates Ltd
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Received on Tue Mar 03 2015 - 11:03:41 CET

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