[SystemSafety] Maintaining Safety Cases Over Time

[paul_e.bennett at topmail.co.uk]

On 04/10/2016 at 4:00 PM, "Carl Sandom" <carl at isys-integrity.com> wrote:

[%X]

>A core system (call it System X) was developed over a number of 
>years along with a Safety Case and it is now in service. Over 
>time, other 'systems' are being connected to System X (Systems Y 
>or Z) to either replace existing functionality or to introduce new 
>functionality. I don't mean System X software updates here; I'm 
>referring to the connection of other systems that are developed 
>independently.

Safety Cases belong to the project. Systems and sub-systems, like 
components, should be supported by a body of evidence for the 
Performance factors such as the Functional Safety achieved in 
terms of that component's interfaces and observable behaviours 
at those interfaces. Dealing with such issues between components 
at the interfaces keeps the knowledge about system behaviour 
identifiably bounded to the shared interfaces.

Coupling sub-systems (perhaps bought in items) to achieve the 
goals of the project should be subject to a review of how well such 
sub-systems meet the requirements and Functional Safety 
requirements.

Once a project has completed (been commissioned and is in 
operation) any changes (adding or subtracting sub-systems) should 
be considered a new project. That new project may take the existing 
safety case as a basis but will have to develop a new safety case for 
the entire project.

Regards

Paul E. Bennett IEng MIET
Systems Engineer

-- 
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Paul E. Bennett IEng MIET.....<email://Paul_E.Bennett@topmail.co.uk>
Forth based HIDECS Consultancy.............<http://www.hidecs.co.uk>
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