Re: [SystemSafety] Critical Design Checklist

From: Matthew Squair < >
Date: Tue, 27 Aug 2013 19:12:20 +1000

Not so much a list but a comment that the items in such a list should possess orthogonality, decidability, atomicity, criticality and a rationale.

The criticality should address Martyn's 'and what then' comment.

On Tuesday, 27 August 2013, Martyn Thomas wrote:

> On 26/08/2013 21:37, Driscoll, Kevin R wrote:
> For NASA, we are creating a Critical Design Checklist:****
> *Objective*****
> - *A checklist for designers to help them determine if a
> safety-critical design has met its safety requirements*****
> Kevin
> For this purpose, I interpret your phrase "safety requirements" for a
> "safety-critical design" as meaning that any system that can be shown to
> implement the design correctly will meet the safety requirements for such a
> system in some required operating conditions.
> Here's my initial checklist:
> 1. Have you stated the "safety requirements" unambiguously and completely?
> How do you know? Can you be certain? If not, what is your confidence level
> and how as it derived?
> 2. Have you specified unambiguously and completely the range of operating
> conditions under which the safety requirements must be met? How do you
> know? Can you be certain? If not, what is your confidence level and how as
> it derived?
> 3. Do you have scientifically sound evidence that the safety-critcal
> design meets the safety requirements?
> 4. Has this evidence been examined by an independent expert and certified
> to be scientifically sound for this purpose?
> 5. Can you name the both the individual who will be personally accountable
> if the design later proves not to meet its safety requirements and the
> organisation that will be liable for any damages?
> 6. Has the individual signed to accept accountability? Has a Director of
> the organisation signed to accept liability?
> Of course, there is a lot of detail conceled within these top-level
> questions. For example, the specification of operating conditions is likely
> to contain detail of required training for operators, which will also need
> to be shown to be adequate.
> But there's probably no need to go into more detail as you will probably
> get at least one answer "no" to the top six questions.
> What will you do then?
> Regards
> Martyn

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