Re: Ariane 5 - not an exception?

[jsa@alexandria (Jon S Anthony)]

In article <4totv7$o9f@goanna.cs.rmit.edu.au> rav@goanna.cs.rmit.edu.au (++           robin) writes:

> ---The choice of language is indeed very relevant.
> What I wrote in an earlier posting on this topic is highly
> apt:

Not in this particular case.  It could have been written in anything and
it would not have made a difference (assuming it was "correctly" written,
i.e., conforming to spec.

> 	>Had the designers of the system allowed the
> 	>implementors to use Ada exception mechanisms fully 
> 	>and properly they could have localized the failure
> 	>to, at worst, the alignment function
> 
> ---But all it needed was a check that the value was in range.
> Such checks had been included on other similar conversions in
> the vicinity!

Irrelevant.  The point is that the requirements stated that the program
was to proceed as it did.  As several have pointed out this was not a
"programming" error.


> 	>(which 
> 	>was not necessary at the time of the failure anyway)
> 
> ---what?  The OBC was using the attitude information to
> direct the nozzles.  It was their [the nozzles] sudden change

The point is the particular system in question was only relevant _prior_
to launch.  Since it was clearly after launch that the failure happened
it should have been irrelevant.


> "This project might well have been written in PL/I, which

First, PL/I has nothing "extra" here at all.  Second, if the thing had
been written in PL/I and it had been in conformance with the
requirements, the thing would have failed.  Of course, you could claim
that were it written in PL/I it would not likely be in conformance and
then it might not have failed.  Shrug.

/Jon

-- 
Jon Anthony
Organon Motives, Inc.
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Belmont, MA 02178

617.484.3383
jsa@organon.com