[SystemSafety] SCSC

[Olwen Morgan]

On 17/07/2019 11:24, Jon Hind wrote:
> Well that was a nostalgic link - who remembers (about 1993 at BAFTA, 
> London ? ) a stand-up row between a speaker who was claiming many 9's 
> - at least 5 or possibly 6 for his controller and an audience member 
> (next to, but not me) who definitely disagreed ?
> Thinking about it it may have been an InstMC event not SCSC.
>
I've yet to see a software system reliability calculation that I find 
anywhere near convincing. Nobody ever seems minded to check whether the 
statistical independence assumptions on which the modelling relies are 
actually satisfied by the system under consideration. And that's quite 
apart from even harder issues of system performance drift, which can 
easily invalidate critical invariance assumptions. If you raise this 
sort of thing as an issue, you tend to get called a pedant - even if all 
you ask for is relevant caveats to be put in the system documentation.

Olwen


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