Re: [SystemSafety] Statistical Assessment of SW With Deliberate Unreliability for a SIL requirement

From: jean-louis Boulanger < >
Date: Wed, 21 Jan 2015 14:15:57 +0100


I am surprised ....

I read "Can such SW be presented as "black box" with statistical evidence of its fitness for purpose, and accepted for use based on the statistical assessment?"

For software it's not possible to have statistical evidence. the failure is 1 (yes the software have fault and failure appear)

The DAL/SSIL ... help us to replace statistical by confidence level

for unspecified cod,n deactivated code e and/or dead code ... we have some recommandation related to the design assurance level

2015-01-21 14:08 GMT+01:00 RICQUE Bertrand (SAGEM DEFENSE SECURITE) < bertrand.ricque_at_xxxxxx

> If it is unspecified and cannot be activated, wouldn’t it be considered as
> dead code under DO ?
>
>
>
> Bertrand Ricque
>
> Program Manager
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> Bertrand.ricque_at_xxxxxx >
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>
> *From:* njtudor_at_xxxxxx > Tudor
> *Sent:* Wednesday, January 21, 2015 2:07 PM
> *To:* RICQUE Bertrand (SAGEM DEFENSE SECURITE)
> *Cc:* Peter Bernard Ladkin; The System Safety List
> *Subject:* Re: [SystemSafety] Statistical Assessment of SW With
> Deliberate Unreliability for a SIL requirement
>
>
>
> Under Do, not on statistical evidence. The functionality has to be shown
> that it cannot be activated unintentionally and this is not done through
> statistical analysis...."the one in a million chance happens 9 times out
> 10" [Pratchet]
>
>
> Nick Tudor
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> Tudor Associates Ltd
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> On 21 January 2015 at 12:59, RICQUE Bertrand (SAGEM DEFENSE SECURITE) <
> bertrand.ricque_at_xxxxxx >
> Do you think it violates ARP and DO ?
>
> Bertrand Ricque
> Program Manager
> Optronics and Defence Division
> Sights Program
> Mob : +33 6 87 47 84 64
> Tel : +33 1 58 11 96 82
> Bertrand.ricque_at_xxxxxx >
> -----Original Message-----
> From: systemsafety-bounces_at_xxxxxx > systemsafety-bounces_at_xxxxxx > Bernard Ladkin
> Sent: Wednesday, January 21, 2015 11:30 AM
> To: The System Safety List
> Subject: [SystemSafety] Statistical Assessment of SW With Deliberate
> Unreliability for a SIL requirement
>
> I am working with others on a reformulation of IEC 61508 Part 7 Annex D,
> on the statistical assessment of software presented with black-box
> functionality.
>
> Rainer Faller brought up an interesting example. He has seen SW which is
> proposed to be used in a safety-related application, which has a Safety
> Requirements Specification (SRS) in that application, and which has a
> "Debug/Maintenance" mode, triggered by a specific input sequence known to
> the SW developer of course, but not necessarily to the system developer who
> wishes to use it in the new safety-related application.
>
> Can such SW be presented as "black box" with statistical evidence of its
> fitness for purpose, and accepted for use based on the statistical
> assessment?
>
> I've written a White Paper on the case, RVS White Paper 8, available at
> http://www.rvs.uni-bielefeld.de/publications/WhitePapers/LadkinFallerExample20150101.pdf
>
> PBL
>
> Prof. Peter Bernard Ladkin, Faculty of Technology, University of
> Bielefeld, 33594 Bielefeld, Germany Je suis Charlie
> Tel+msg +49 (0)521 880 7319 www.rvs.uni-bielefeld.de
>
>
>
>
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-- 
Mr Jean-louis Boulanger



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