[SystemSafety] Software reliability (or whatever you would prefer to call it)

[Yiannis I Papadopoulos]

" Software essentially boils down to a string of one's and nought's. Given the same inputs (and that always comes from the chaotic environment) then the output will always be the same.  It therefore makes no sense to talk about 'software reliability' "

The premise is true but does the conclusion follow?

Take the example of throwing a dice.

If you know everything about the dice and its environment and apply the laws of physics you can determine the outcome. You can be god, replicate the exact conditions and you will get the same outcome every time (... no Heisenberg please ... if quantum mechanics introduced any real randomness in the world as we know it, we would be in real trouble :)

So, what is the purpose then of talking about randomness,  probability and statistics to describe such phenomena? I think the answer is that it is often the best, sometimes the only way, to reason about complex deterministic processes. It is done all the time in science, why not in software?

--
Yiannis Papadopoulos
http://www2.hull.ac.uk/science/computer_science/our_staff/staff_profiles/yiannis_papadopoulos.aspx

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