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,d901a50a5adfec3c X-Google-Attributes: gid103376,public X-Google-Thread: 1094ba,9f0bf354542633fd X-Google-Attributes: gid1094ba,public From: robin Subject: Re: Fortran or Ada? Date: 1998/10/05 Message-ID: <3618299b.0@139.134.5.33>#1/1 X-Deja-AN: 397772765 X-Trace: nsw.nnrp.telstra.net 907553360 139.134.5.33 (Mon, 05 Oct 1998 12:09:20 EST) Organization: Telstra Big Pond Direct NNTP-Posting-Date: Mon, 05 Oct 1998 12:09:20 EST Newsgroups: comp.lang.fortran,comp.lang.ada X-Complaints-To: abuse@telstra.net Date: 1998-10-05T00:00:00+00:00 List-Id: Niklas Holsti 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. No guessing was involved. Any kind of interrupt is treated as a hardware error. This was the fundamental flaw in their assumptions. > They guessed > "hardware error". In the context of Ariane 4, it hasn't been shown that > this was the wrong thing to do. The Report criticized the assumption [that sofware errors couldn't happen]. > 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.)