Re: [SystemSafety] Software reliability (or whatever you would prefer to call it)

From: Peter Bernard Ladkin < >
Date: Wed, 11 Mar 2015 09:42:08 +0100


The obvious point is that the inputs not only did not have the same distribution (in Flight 501), but had not been seen before in the previous use (in the Ariane 4). So yes, our document covers this clearly. In the current Annex D, the condition is well hidden.

PBL Prof. Peter Bernard Ladkin, University of Bielefeld and Causalis Limited

> On 11 Mar 2015, at 08:50, David MENTRE <dmentre_at_xxxxxx >
> Dear Mr. Ladkin,
>
> Le 10/03/2015 12:16, Peter Bernard Ladkin a écrit :

>> The standard resolution of questions as to whether math is correctly or incorrectly used is to
>> provide a proof or a counterexample.

>
> I'll try a counter-example ;-) or more exactly I would like to see your reasoning on software reliability and probabilities on the following example.
>
> Consider reuse of a Inertial Reference System module from Ariane 4 to Ariane 501.
> ..............
> Would your proposal on Annex D address this case? Under which conditions a software module can be assessed reliable and reused?


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systemsafety_at_xxxxxx Received on Wed Mar 11 2015 - 09:42:19 CET

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