[SystemSafety] Critical Design Checklist

[Peter Bishop]

This may be wandering into the realms of system safety, but I would 
extend 1, 2 because we need to accommodate human fallibility and 
limitations in knowledge by having some kind of fallback or recovery 
strategy.

A If there are residual doubts about requirements or implementation, are 
there any alternative systems that can maintain safety? (defence in 
depth principle)
B What what features exist for identifying malfunctions in operation, 
and implementing design rectifications over the operating lifetime.

Peter Bishop
Adelard LLP

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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-- 

Peter Bishop
Chief Scientist
Adelard LLP
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