Re: Papers on the Ariane-5 crash and Design by Contract

[Ken Garlington <GarlingtonKE@lmtas.lmco.com>]

John McCabe wrote:
> 
> jezequel@irisa.fr (Jean-Marc Jezequel) wrote:
> 
> >In article <33307a43.1705970@news.demon.co.uk>, john@assen.demon.co.uk (John McCabe) writes:
> >>I am a bit unhappy with the way the paper has been written. As I
> >>mentioned in another posting on this thread, the fundamental problem
> >>was that the developers did not have Ariane 5 trajectory data to work
> >
> >Yes this is true. But, since the SRI was reused from Ariane4, the problem
> >is not with developers, but with the *integration* team.
> 
> I think there was a bit more to it than just getting one off the
> shelf. I quote from the inquiry report:
> 
> "The design of the Ariane 5 SRI is practically the same as that of an
> SRI which is presently used on Ariane 4, particularly as regards the
> software."
> 
> Note Practically the same - not identical.
> 
> >AFAIK, the integration team had the possibility to work with Ariane 5 trajectory data,
> >and in the ideal case where Design by Contract would have been used on the SRI,
> >they would have the opportunity the check it wrt the environment of Ariane5.
> 
> Again, I quote:
> 
> "There is no evidence that any trajectory data were used to analyse
> the behaviour of the unprotected variables, and it is even more
> important to note that it was jointly agreed not to include the Ariane
> 5 trajectory data in the SRI requirements and specification."

What I think he's saying is that if the integration team had done a
proper test, and
had used Eiffel, then the problem would have been detected. Left
unstated is the
observation from the final report that if a proper test had been done,
the problem would
have been detected even *without* the added assertions. Of course, this
statement
would make it more difficult to imply to the uninformed that "Ariane V
would not
have happened if it was programmed in Eiffel"...

> 
> Best Regards
> John McCabe <john@assen.demon.co.uk>

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