[SystemSafety] Relationship of reliability and safety (was Re: New paper on MISRA C)

[Stefan Winter]

Hi Paul,

On 09/13/2018 07:57 AM, Paul Sherwood wrote:
> On 2018-09-12 16:05, Peter Bernard Ladkin wrote:
>> I suggest the following characterisation is somewhat misleading:
>>> MIT and others have successfully debunked the notion that system 
>>> safety is correlated with component reliability
> 
> OK, I'll try to be clearer. Engineering A Safer World states, with clear 
> examples and justification:
> 
> "High reliability is neither necessary nor sufficient for safety."

could you please state where? The PDF search is highly unreliable for 
that document. ;)

To rebut a statement of such generality as "reliability is 
necessary/sufficient for safety" is easy if you read it as meaning "for 
all possible systems". One counterexample and you're done. I wonder, 
though, if such a statement is really meaningful, because the rebuttal 
also works in the opposite direction: "For any possible system 
reliability is never necessary for safety". I would assume that this is 
easier to disprove than to prove.

Cheers,
Stefan