Re: [SystemSafety] Degraded software performance [diverged from Fault, Failure and Reliability Again]

From: RICQUE Bertrand (SAGEM DEFENSE SECURITE) < >
Date: Thu, 5 Mar 2015 11:47:50 +0100


As a member of the maintenance team, my opinion is that :

Annex D is for the moment poorly related to the body of the standard: i.e. the standard does not account for probability of failure of software as a design input or as a performance objective for new software. The issue seems only relevant, for the moment for existing software associated with the intention to "reuse" it.

The question of the intended scope of applicability of a quantification of software performance based on probabilities thus arises. Limited to "reuse" or extended to "new". This will have to be clearly stated somewhere.

It will be difficult to do some progress if we are not able to agree on:

* Do we consider software without hardware ? Which is the mainstream of the existing standard.
* If we think it is not relevant to segregate HW and SW, is it realistic to foresee the consequential modifications we would have to implement in part 1 and 2 of the standard ?
* Are we measuring:
     *an intrinsic property of the software (failure rate or probability)?
     *a property of the software development process (quality of the requirements, quality of the tests)?
     *a property of the SW/HW integration ?
     * an aggregate property of all of the above ?

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-----
Sent: Thursday, March 05, 2015 11:24 AM
To: Nick Tudor; The System Safety List
Subject: Re: [SystemSafety] Degraded software performance [diverged from Fault, Failure and Reliability Again]

Nick,

I do think we need to be clear about the situation with IEC 61508 Part 7 Annex D.

On 2015-03-05 10:41 , Nick Tudor wrote:
> .. There is a plan to
> update a standard IEC61508 with material about how one might use
> software reliability in safety systems.

There is a plan to update a 17-year-old section, Part 7 Annex D, about statistical evaluation of software in IEC 61508.

> Standards are supposed to represent the consensus of the community and
> it has been reported by others on this list that many standards do not recognise this approach.

The new version of IEC 61508 will represent the consensus of the Maintenance Team charged with updating it, and the vote of approval from participating national committees.

If we don't fix Annex D in the forthcoming maintenance cycle, it will stay the same as it is now; I doubt very much if it will be deleted.

I'm just one person. I would imagine there are 25-30 active members of the maintenance team, some of whom are on this list.

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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systemsafety_at_xxxxxx Received on Thu Mar 05 2015 - 11:48:10 CET

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