From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,267eec8ad557a7d0 X-Google-Attributes: gid103376,public From: Ken Garlington Subject: Re: ARIANE-5 Failure Date: 1996/06/12 Message-ID: <31BEA5F1.33FA@lmtas.lmco.com>#1/1 X-Deja-AN: 159860464 references: <834097751.22632.0@assen.demon.co.uk> <31B7A88D.446B@lri.fr> <31B7DEDD.E2A@lmtas.lmco.com> <31bc75ed.1932371@news.cableol.net> <31BEBA98.167EB0E7@escmail.orl.mmc.com> content-type: text/plain; charset=us-ascii organization: Lockheed Martin Tactical Aircraft Systems mime-version: 1.0 newsgroups: comp.lang.ada x-mailer: Mozilla 2.02 (Macintosh; I; 68K) Date: 1996-06-12T00:00:00+00:00 List-Id: Theodore E. Dennison wrote: > > Still, if thy had named their variables Radius.Velocity_Smoothed_N and > Radius.Velocity_N (their language probably didn't even allow this), the > odds of this error being discovered by someone before the failure would > have been MUCH greater. Well, this notation would have to have been used in the requirements to be meaningful, and I don't think most systems engineers want to write math equations in Ada! There was a study a few years back by a Dr. Avezziani [sp] attempting to show the worth of N-version programming. He had several teams use a high-quality software development process to build a subset of a flight control system. There was only one common-mode error found. Each team had been given a photocopy of the control law diagrams to implement. There was a number, something like 5.122, on one of the gains. However, the smudged photocopy made it look like 5,122. Each team used the constant 5,122 in their code. (I'm not sure how this proved the use of N-version programming, but that's another issue). It's amazing how tiny changes in dense notations add up to big errors. Maybe the real lesson learned is to use better equation editors, and avoid the Xerox machine! > > -- > T.E.D. > | Work - mailto:dennison@escmail.orl.mmc.com | > | Home - mailto:dennison@iag.net | > | URL - http://www.iag.net/~dennison | -- LMTAS - "Our Brand Means Quality"