Re: Ariane5 FAQ

[Vinzent Hoefler <ada.rocks@jlfencey.com>]

Richard Riehle wrote:

>Vinzent Hoefler wrote:
>
>Bertrand Meyer published a controversial article suggesting
>that, had they used design by contract ( a la Eiffel) this could
>not have happened.

Probably you also read
<URL:http://www.flash.net/~kennieg/ariane.html>?

>  While I don't agree that Eiffel would have
>been better for the job, a contract model such as that found in
>SPARK might have been successful in detecting the design
>error early on.

I would even doubt that, because the design was based on the
assumption that certain values would not exceed their range. The
programmers knew it wouldn't happen in normal operation, so I think it
is very likely they would have told the prover, it won't do that. So
it would have changed exactly nothing at this point.
But, *perhaps* it would have been slightly better documented because
someone should justify such a decision in the proof-process and so
some people might have taken a closer look at these assumptions and
then concluded "Houston, we've got a problem." ;) But that's just a
guess. Nobody seemed to check the requirements changes between the IRS
for Ariane 4 and 5 anyway...


Vinzent.

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