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=-1.9 required=5.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,f039470e8f537101 X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2003-07-29 14:52:32 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!logbridge.uoregon.edu!arclight.uoregon.edu!wn13feed!worldnet.att.net!204.127.198.203!attbi_feed3!attbi.com!sccrnsc04.POSTED!not-for-mail Message-ID: <3F26EC89.4030205@attbi.com> From: "Robert I. Eachus" User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.0.2) Gecko/20021120 Netscape/7.01 X-Accept-Language: en-us, en MIME-Version: 1.0 Newsgroups: comp.lang.ada Subject: Re: Ariane5 FAQ References: <1058968422.225561@master.nyc.kbcfp.com> <3F200AD0.94F79098@adaworks.com> <7u9Ua.13412$634.10307@nwrdny03.gnilink.net> <3F215120.1040706@attbi.com> <1059151910.357790@master.nyc.kbcfp.com> <3F248CEE.5050709@attbi.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit NNTP-Posting-Host: 66.31.71.243 X-Complaints-To: abuse@comcast.net X-Trace: sccrnsc04 1059515548 66.31.71.243 (Tue, 29 Jul 2003 21:52:28 GMT) NNTP-Posting-Date: Tue, 29 Jul 2003 21:52:28 GMT Organization: Comcast Online Date: Tue, 29 Jul 2003 21:52:32 GMT Xref: archiver1.google.com comp.lang.ada:40970 Date: 2003-07-29T21:52:32+00:00 List-Id: Berend de Boer wrote: > The point is that the requirements should be *in the code*. That's > where they belong. Not sure if this would have made a difference, but > if you want to reuse code, you should now the conditions under which > it should work. If programmers just grab code and reuse it without > looking at those preconditions, well, you're not doing your job right. Software requirements may belong in the software, but I don't buy the idea that the SYSTEM requirements belong in the software. Managing system requirements is a process similar to managing software development, which often, as Dave Emery says, makes software engineers the system engineers of last resort. But system requirements belong in the system spec. There also needs to be a mapping from those requirements to subcomponents and subsystems (including software). There also needs to be a mapping from the system requirements to how testing to meet each requirement will be done. I am a big believer in designing software to not only meet requirements, but to make it easy to test/validate that those requirements are met. But putting hardware requirements in the software is a waste of time and effort. Since most often SYSTEM requirements are met by a combination of software and hardware, the requirements in the software are usually derived requirements. But I don't think the mapping from system requirements to software requirements belongs in the code. And that was where the disconnect was here. Even if every software module had a block comment that indentified the requirements it met, in this case the disconnect still would have occurred. The software requirement for the alignment software to run for 40 seconds after MEI could have been perfectly documented in the software. But only by accident would someone notice that the requirement it was derived from only applied to the Ariane 4--unless someone who had the overall systems engineering responsibility found that the software did not match the (actual Ariane 5) system requirements. As it was, the fact that the alignment software did run for 40 seconds after MEI was noted, but the decision was made not to change it as it would require revalidating the software. Duh! See my previous posts. You can never reuse system level tests, so the testing should have been done whether or not the software was modified. It is this retest that would have discovered that the control laws did not match the Ariane 5, and probably that the alignment software running after MEI was no longer required. (But whether that was noticed or not, the NEED to actually do the "hardware in the loop" full-up flight systems simulation would have found it.) -- "As far as I'm concerned, war always means failure." -- Jacques Chirac, President of France "As far as France is concerned, you're right." -- Rush Limbaugh