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From: Ken Garlington <GarlingtonKE@lmtas.lmco.com>
Subject: Re: Ariane-5: can you clarify? (Re: Please do not start a
Date: 1997/03/21
Message-ID: <3332BA72.72F8@lmtas.lmco.com>#1/1
X-Deja-AN: 227299822
References: <97031917192223@psavax.pwfl.com>
Organization: Lockheed Martin Tactical Aircraft Systems
Newsgroups: comp.lang.ada
Date: 1997-03-21T00:00:00+00:00
List-Id: <comp.lang.ada>


Marin David Condic, 561.796.8997, M/S 731-93 wrote:
> 
>     I've heard of projects where they design two different computers
>     and two different sets of software deliberately to be dissimilar
>     so that the problem of a common design flaw is avoided. (I imagine
>     that thi$ $ort of $tuff gets *real $pendy!) But then,
>     one can always object that they are both operating to the same set
>     of requirements and if a requirement is bad, both will do the
>     same, wrong thing and fail.

Not only can they object, there is a significant amount of experimental
and anecdotal evidence that says the error will be in the requirements.
See, for example, the work of Levison and Knight.

Ariane-5 is a perfect example of this. As the final report says, the
specification did not contain the Ariane V flight profile as a
requirement.
Given that, I would not be at all surprised if the same design fault
occured in multiple design variants.

>     Nothing built by the hand of man is
>     without flaws. Guess we just gotta learn to live with an
>     occasional failure, 'cause they're gonna happen!
> 
>     MDC
> 
> Marin David Condic, Senior Computer Engineer    ATT:        561.796.8997
> M/S 731-96                                      Technet:    796.8997
> Pratt & Whitney, GESP                           Fax:        561.796.4669
> P.O. Box 109600                                 Internet:   CONDICMA@PWFL.COM
> West Palm Beach, FL 33410-9600                  Internet:   CONDIC@FLINET.COM
> ===============================================================================
>         In Vegas, I got into a long argument with the man at the
>         roulette wheel over what I considered to be an odd number.
> 
>             --  Steven Wright
> ===============================================================================

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