Re: Ariane 5 failure - latest S/W tech vs. cold hard facts

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

Robert S. White wrote:
> 
> In article <dewar.844517570@schonberg>, dewar@schonberg.cs.nyu.edu says...
> 
> >There are certainly cases where careful consideration of these three factors
> >still results in a decision to use less hardware and more complex software,
> >but I think we have all seen cases where such decisions were made, and n
> >in retrospect turned out to be huge mistakes.
> 
>   In business when making hard decisions about embedded systems products,
> such studies are almost always made.

In my experience, both statements are true. Such studies are often made, and I have 
also seen cases where they weren't made, or were done poorly. I have no idea what the 
percentages are for:

  * the study was done correctly
  * the study was not done correctly (or not done at all), but the decision turned
    out to be right anyway
  * the study was done incorrectly, the answer was wrong, and no one ever discovered
    it was wrong (because no one ever looked at the final cost, etc.)
  * the study was done incorrectly, the answer was wrong, someone found out it was
    wrong, but didn't broadcast it to the general public (would you?)

Overall, I'd say we'll never know. As a colleague of mine said: "How many systems out 
there have a bug like the Ariane 5, but just never hit that magic condition where the 
bug caused a failure?" Just think: A little less acceleration on takeoff, and we'd 
think Arianespace made a wonderful decision by reusing the Ariane 4 -- look at all the 
money they saved! It might have been mentioned in the Reuse News as a major success :)
 
I've got a few minutes, so I'll mention another of my favorite themes at this point 
(usually stated in the context of preparing Ada waivers): It's really hard to 
determine the life-cycle cost of software, particularly over a long period (e.g. 20 
years). There are cost models; sometimes, we even get the parameters right and the 
model comes up with the right answer. Nonetheless, it's tough to consider life-cycle 
costs objectively. That's not an excuse for failing to try, but an acknowledgement 
that it's easy to get it wrong (particularly for new technology).

Software engineering can be _so_ depressing!

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