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: fac41,f66d11aeda114c52 X-Google-Attributes: gidfac41,public X-Google-Thread: 103376,f66d11aeda114c52 X-Google-Attributes: gid103376,public From: Thomas Beale Subject: Re: Critique of Ariane 5 paper (finally!) Date: 1997/08/21 Message-ID: <33FBD62C.3DD3@invest.amp.com.au>#1/1 X-Deja-AN: 265661441 References: <33E503B3.3278@flash.net> <33E8FC54.41C67EA6@eiffel.com> <33E9B217.39DA@flash.net> <33EA5592.5855@flash.net> <33EB4935.167EB0E7@eiffel.com> <33EB754E.446B9B3D@eiffel.com> <33EBE46D.2149@flash.net> <33EF9487.41C67EA6@eiffel.com> <33F22B91.167EB0E7@eiffel.com> <33F7C3C0.446B9B3D@eiffel.com> <33FA748A.35FE@flash.net> Organization: AMP Investments Australia Newsgroups: comp.lang.ada,comp.lang.eiffel Date: 1997-08-21T00:00:00+00:00 List-Id: Robert Dewar wrote: > > There are many ways that one can use to determine if a program is reliable. > For example, in some limited small cases, total proof of correctness may > be a useful tool. Certainly the contstruction of such proofs can be aided > by accurate assertions about the code, but such proofs do not (and cannot) > depend critically on the presence of such assertions. As an observer to this long-winded thread, can I suggest that you define what you mean by reliable? Software engineers such as myself often use the term "correctness" to mean what you seem to be talking about above. I would define "reliability" as the ability of a system to execute correctly over some time, and with "normal" inputs ("robustness" would be a measure of a system handling pathological inputs). Reliability in my experience has often been specified by an mtbf - mean time between failures - figure. So the aspect of quality we are interested in here is longevity of correct operation, not just correct function. So, when you say "reliability", exactly what do you mean? - thomas beale