[SystemSafety] Difference between software reliability and astrology

[Derek M Jones]

Peter,

> What counts is models that work.  We rationalize them
>> after it has been shown that they do a good job of predicting
>> our reality.
> 
> ... In particular, that is not the way it works with the 
> reliability models used for safety-related software for which there are what Littlewood and Strigini called ultra-high 
> dependability requirements.

It does not work this was for software reliability models because
of the lack of evidence of what works or does not work.

Arguments are ego and bluster based, and arguing from authority (your
favorite).

> Similar considerations for continuously-operating software to a Poisson process (or to some renewal process for 
> components, whereby by a limit theorem the entirety behaves Poisson-ly).

I thought that we had agreed that software reliability is not
a Poisson process?

 >                                                                         There is no matching of results ("doing a good
> job of predicting .. reality) because the outcome you are looking for is an absence of something, namely failures. If 
> you see one, or more, it's back to the drawing board with the software.

The same rationale applies to nothing really bad happening because
of the annual sacrifices to the gods.


-- 
Derek M. Jones           Evidence-based software engineering
blog:https://shape-of-code.com