From: molagnon@ifremer.fr (Michel OLAGNON)
Subject: Re: Fortran or Ada?
Date: 1998/10/05
Date: 1998-10-05T00:00:00+00:00 [thread overview]
Message-ID: <6v9s4t$egn$1@ys.ifremer.fr> (raw)
In-Reply-To: 3617AA49.340A5899@icon.fi
In article <3617AA49.340A5899@icon.fi>, Niklas Holsti <nholsti@icon.fi> writes:
>Toon Moene wrote:
>>
>> In my mind, an exception is a sign that the assumptions behind the
>> (physics/mathematics) of your model is wrong, and - even though that pertains
>> to a large extent also to rocket ascent - this would not lead to a reasonably
>> safe procedure here.
>
>Yes, this is one category of exceptions (the other category is where
>exception handling is used to catch rare but foreseeable situations,
>such
>as errors in input data files -- END= and ERR= labels, for example).
>
>It seems that the designers of the Ariane 4 guidance system had this
>view, except that their "model" included the processing hardware in
>addition to the models encoded in the software. To decide how to handle
>the overflow exception, they had to guess which part of their model was
>at fault -- whether the hardware or the software was wrong. They guessed
>"hardware error". In the context of Ariane 4, it hasn't been shown that
>this was the wrong thing to do.
>
At the time of writing the software, it might not have been wrong.
But later on, the launch procedure was changed for Ariane 4, and
the computation no longer needed. IMHO, not removing unnecessary
computations that may have side effects IS a "software error".
The designers failed, IMHO, to note that even if hardware might
be more likely to be wrong than software at time T0, over the whole
expected service life of the system, it was software that had the highest
probability to end up wrong.
>The odds in this guess must depend on how well the software models were
>verified and validated. I haven't seen any claims that the software
>models were not correct for Ariane 4.
>
>Niklas Holsti
>Space Systems Finland Ltd
>(This comment expresses personal opinion and not Space Systems Finland
>policy.)
Michel
--
| Michel OLAGNON email : Michel.Olagnon@ifremer.fr|
| IFREMER: Institut Francais de Recherches pour l'Exploitation de la Mer|
| Centre de Brest - B.P. 70 phone : +33-2-9822 4144|
| F-29280 PLOUZANE - FRANCE fax : +33-2-9822 4650|
| http://www.ifremer.fr/ditigo/molagnon/molagnon.html |
next prev parent reply other threads:[~1998-10-05 0:00 UTC|newest]
Thread overview: 96+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <36068E73.F0398C54@meca.polymtl.ca>
1998-09-22 0:00 ` Fortran or Ada? Gisle S{lensminde
1998-09-22 0:00 ` Jeff Templon
1998-09-22 0:00 ` Rakesh Malhotra
1998-09-22 0:00 ` dewarr
1998-09-23 0:00 ` Jeff Templon
1998-09-23 0:00 ` Corey Minyard
1998-09-24 0:00 ` Craig Burley
1998-09-25 0:00 ` dewarr
1998-09-25 0:00 ` Jonathan Guthrie
1998-09-26 0:00 ` Craig Burley
1998-09-26 0:00 ` dewarr
1998-09-26 0:00 ` Robert B. Love
1998-09-26 0:00 ` Craig Burley
1998-09-24 0:00 ` Joel Seidman
1998-09-24 0:00 ` Marc A. Criley
1998-09-24 0:00 ` dewarr
1998-09-24 0:00 ` Robert I. Eachus
1998-09-24 0:00 ` William Clodius
1998-09-25 0:00 ` dewarr
1998-09-25 0:00 ` dewarr
1998-09-25 0:00 ` Robert I. Eachus
1998-09-25 0:00 ` dewarr
1998-09-25 0:00 ` jbs
1998-09-26 0:00 ` dewarr
1998-09-28 0:00 ` jbs
1998-09-29 0:00 ` Dean F. Sutherland
1998-09-29 0:00 ` Dean F. Sutherland
1998-09-29 0:00 ` Gautier.DeMontmollin
1998-09-29 0:00 ` William B. Clodius
1998-09-30 0:00 ` jbs
1998-09-30 0:00 ` dewarr
1998-09-30 0:00 ` jbs
1998-09-30 0:00 ` William Clodius
1998-09-30 0:00 ` William Clodius
1998-10-03 0:00 ` Niklas Holsti
1998-10-03 0:00 ` Toon Moene
1998-10-03 0:00 ` Niklas Holsti
1998-10-03 0:00 ` Toon Moene
1998-10-04 0:00 ` Niklas Holsti
1998-10-05 0:00 ` Michel OLAGNON [this message]
1998-10-05 0:00 ` Ian St. John
1998-10-05 0:00 ` dewarr
1998-10-05 0:00 ` Ian St. John
1998-10-06 0:00 ` dewarr
1998-10-06 0:00 ` James Giles
1998-10-06 0:00 ` Mark A Biggar
1998-10-06 0:00 ` James Giles
1998-10-07 0:00 ` dewarr
1998-10-07 0:00 ` dewarr
1998-10-06 0:00 ` Toon Moene
1998-10-06 0:00 ` Jonathan Guthrie
1998-10-06 0:00 ` Ian St. John
1998-10-08 0:00 ` Gary L. Scott
1998-10-08 0:00 ` Offtopic Airport Diversion (Was: Fortran or Ada?) Harold Stevens ** PLEASE SEE SIG **
1998-10-08 0:00 ` Ian St. John
1998-10-05 0:00 ` Fortran or Ada? Richard D Riehle
1998-10-05 0:00 ` dewarr
1998-10-06 0:00 ` Michel OLAGNON
1998-10-07 0:00 ` Ian St. John
1998-09-29 0:00 ` Dean F. Sutherland
1998-10-02 0:00 ` Robert I. Eachus
1998-10-02 0:00 ` jbs
1998-10-02 0:00 ` William Clodius
1998-10-03 0:00 ` jbs
1998-10-03 0:00 ` Larry Elmore
1998-10-06 0:00 ` Robert I. Eachus
1998-10-06 0:00 ` Pat Rogers
1998-10-02 0:00 ` Geoff Bull
1998-09-24 0:00 ` Jeff Templon
1998-09-25 0:00 ` Dale Stanbrough
1998-09-30 0:00 ` Daniel Barker
1998-09-30 0:00 ` Lawrence Kirby
1998-10-01 0:00 ` Aaron Crane
1998-10-02 0:00 ` Fortran or Ada or gobbledygook? Wes Groleau
1998-10-05 0:00 ` Fortran or Ada? Terry Devine
1998-09-25 0:00 ` dewarr
[not found] ` <6udre0$ha1$1@nnrp1.dejane <6utg60$h6l$1@nnrp1.dejanews.com>
1998-10-01 0:00 ` robin_v
1998-09-22 0:00 ` Corey Minyard
1998-09-22 0:00 ` Larry Kilgallen
1998-09-23 0:00 ` Frank Ecke
1998-09-23 0:00 ` bglbv
1998-09-23 0:00 ` Robert I. Eachus
1998-09-24 0:00 ` Richard D Riehle
1998-09-23 0:00 Marin David Condic, 561.796.8997, M/S 731-96
-- strict thread matches above, loose matches on Subject: below --
1998-09-23 0:00 Marin David Condic, 561.796.8997, M/S 731-96
1998-09-23 0:00 ` Gisle S{lensminde
1998-09-24 0:00 ` John McCabe
1998-09-24 0:00 ` Dean F. Sutherland
1998-09-24 0:00 ` Gisle S{lensminde
1998-09-24 0:00 ` Samuel T. Harris
1998-09-24 0:00 Walt Brainerd
1998-09-25 0:00 ` Robert I. Eachus
1998-09-25 0:00 ` dewarr
1998-10-05 0:00 Condic, Marin D.
1998-10-05 0:00 robin
1998-10-05 0:00 Robert I. Eachus
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