[SystemSafety] Correctness by Construction

[Peter Bishop]

On 14/07/2020 10:54, Michael Jackson wrote:
> (e)  'Software-based' systems in general, and cyber-physical systems in particular, are bipartite. One part is the software itself, executed solely by the processor hardware; the other part is the governed physical 'problem world' outside the computer. If Correctness by Construction is applied only to the software itself, it can achieve only a limited reduction of system defects. 
>
> (f)  In a cyber-physical system the core development product is the behaviour of the whole system, emerging from the interaction of both of its parts. Development is indeed a programming task, but it is programming the whole system, not just the software part. The heterogeneous nature of the system---quasi-formal software joined with the non-formal problem world---poses a real difficulty. But erecting a logical firewall between the two parts and treating them in effective isolation is not a perfect solution. 

That is my view as well.

The "correctness" achieved by CbyC  does not guarantee that the
requirements assigned to the software will address the real world problem.

-- Peter

 

-- 

Peter Bishop
Chief Scientist
Adelard LLP
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