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

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

Alexander Anderson wrote:
> 
>     There are a number of points skirted around in the Inquiry Board's
> Ariane 5 Failure Report, that are telling:
> 
[several quotes from the report snipped]
> 
>     These phrases, "A DECISION WAS TAKEN", "FOR A NUMBER OF REASONS",
> and to make sure reviews "CONSIDER THE SUBSTANCE OF ARGUMENTS", suggest,
> to me, a picture of a deeper malaise running through the history of the
> project organisation.
> 
>     In other words, if you got people in private, you'd hear individual
> professional worries over morale, over how things were being handled,
> and they'd insist you kept them anonymous.  The last excerpt, R9, from
> the recommendations, is to my mind, particularly telling.

The report could be read that way; however, I think another
interpretation
is also possible:

First, the time frame is important when reading excerpts from the
report.
Several of the "decisions" cited appeared to occur during the original
development of the IRS for the Ariane 4. In that context, those
decisions
could be defended.

The report does note that the Ariane 5 has a significantly different
profile than the Ariane 4. However, it also appears that the
IRS *technical* team did not have access to that information:

"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."

I read this as a decision by *management* to leave out this information.
In past projects where I have seen this happen, it is usually
because the managers involved have a lot of systems experience,
but not much software experience. They are making what they consider
to be reasonable decisions based on their background. Unfortunately,
that oftentimes causes problems for systems which have transitioned
from hardware-intensive to software-intensive designs over the years -
such as inertial reference systems.

So, it may have been less a consideration of the technical team
being pressured to make a bad choice, and more of the management
team making a decision without the technical team even being
aware of it. Who knows?

> 
> Sandy
> 
> /*
> --
> //    Alexander Anderson  <sandy@almide.demon.co.uk>
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