[SystemSafety] Omitting future considerations from safety cases

[John Spriggs]

Hi Daniel,
If the means to provide your future capability is already in the system,
you need to argue that it cannot "go off accidentally" or, if it were to do
so, that it would not mess up any of the safety features upon which your
safety case depends.  If there are just "hooks" in the system onto which
you will build the future functionality, you need to declare that they are
there, and that they do not interfere with anything.  In either case, you
need to think about the assurance strategy for adding the new capability in
future and how to maintain the safety case throughout operation.  Your
safety case assessors will be  particularly interested in that strategy if
you have to maintain the existing services in operation whilst adding the
new ones.
As for decluttering, the best way is not to describe the proposed future
capabilities in any detail - I have seen assurance cases that read like a
marketing document and it was not clear what was actually being assured at
that stage of the programme.
Another source of clutter is repetition; if, for example, you have chosen
to present your argument using a graphical notation, do not also present it
in text for those unfamiliar with the notation - rather provide training or
a handy guide.  I have seen an assurance document with the same argument
presented using three different methods - that will be a nightmare to
maintain as the system evolves...


John

On Wed, 28 Sept 2022 at 11:31, Daniel Grivicic <grivsta at gmail.com> wrote:

> Thank you.
>
> I can see that future considerations are important; however, consider the
> context. So I can see a question I need to contemplete is: Will omitting
> possible future uses benefit the safety case by decluttering it, or are
> they essential to comprehension?
>
> -Daniel.
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