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=0.2 required=5.0 tests=BAYES_00,INVALID_MSGID, REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,59dddae4a1f01e1a X-Google-Attributes: gid103376,public From: JP Thornley Subject: Re: Need help with PowerPC/Ada and realtime tasking Date: 1996/05/30 Message-ID: <637048781wnr@diphi.demon.co.uk>#1/1 X-Deja-AN: 157670282 x-nntp-posting-host: diphi.demon.co.uk references: <1026696wnr@diphi.demon.co.uk> <355912560wnr@diphi.demon.co.uk> x-mail2news-path: disperse.demon.co.uk!post.demon.co.uk!diphi.demon.co.uk organization: None reply-to: jpt@diphi.demon.co.uk newsgroups: comp.lang.ada Date: 1996-05-30T00:00:00+00:00 List-Id: In article: eachus@spectre.mitre.org (Robert I. Eachus) writes: > ......... There are failure rates for the > sensors, some tied to the geometry of the radar or the signatures of > the target, and some failures due to the algorithms (and software) > used. As I read this, the failure rate is connected with the choice of algorithm. If this is not specified in the requirements then these failure rates (resulting from the algorithm chosen by the software engineer) have to be brought into the design and code level hazard analyses, so that they can be fed into the wider system safety assessment. But the point that this responded to is not talking about failure rates of algorithms in this sense, but failure rates of the implementation in producing the 'correct' value according to the algorithm specification (and yes, the software engineer is responsible for the error bounds on the implementation method chose). [snip] > Last but not least, there is the ugly ghost of Godel. Systems > below a certain level of complexity can be 100% right or 100% wrong. > Above that line, software systems look a lot more like hardware. I wonder if this is where computer science and (my sort of) software engineering part company. Or do you while away the hours when travelling by Boeing 777 wondering whether the flight control computers are about to be presented with an undecidable proposition? > > -- > > Robert I. Eachus > > with Standard_Disclaimer; > use Standard_Disclaimer; > function Message (Text: in Clever_Ideas) return Better_Ideas is... > > -- ------------------------------------------------------------------------ | JP Thornley EMail jpt@diphi.demon.co.uk | ------------------------------------------------------------------------