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: 103376,609812fc77a5d4f9 X-Google-Attributes: gid103376,public From: jsa@alexandria (Jon S Anthony) Subject: Re: Ariane-5: can you clarify? (Re: Please do not start a Date: 1997/03/20 Message-ID: #1/1 X-Deja-AN: 226847329 Distribution: world References: <97031917192223@psavax.pwfl.com> Organization: PSI Public Usenet Link 19 Mar 1997 17: 19:22 -0500 Newsgroups: comp.lang.ada Date: 1997-03-20T00:00:00+00:00 List-Id: In article <97031917192223@psavax.pwfl.com> "Marin David Condic, 561.796.8997, M/S 731-93" writes: > It's true that software is historically more apt to have design > errors in it than hardware. But its important to note that the > reason for the dual redundancy on computers such as the Ariane is > that hardware breaks. Software never breaks or wears out. I agree it never wears out. From a certain point of view I can also see why you might say it never breaks. But in that case, I would expect that the prudent assumption would be that it is simply _always_ broken. Not true per se, but a much safer rule of thumb than the opposite. > In a sense, you're asking the question of the software: "Do I > trust this set of logical rules to operate my vehicle properly?" That's actually only a small piece of it. There are all the other issues even assuming the correctness of the rules: Were they communicated correctly? Were they implemented correctly? Will they be used in the proper context for which they were conceived? Etc. Generally speaking, software practice does a much more miserable job of this than hardware, with the exception of engine and flight control software. > So in a way, the software is safer because, while both hardware > and software can suffer a fatal design flaw, the software cannot > break or wear out in usage. It can simply _always_ have been broken. Just waiting to blow up in your face. > same, wrong thing and fail. 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! Absolutely agree. /Jon -- Jon Anthony Organon Motives, Inc. Belmont, MA 02178 617.484.3383 jsa@organon.com