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Re: Space probes was Re: in praise of type checking

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In article <amzlq.8514$kJ5.8234@newsfe03.iad>,
 Arved Sandstrom <asandstrom3minus1@eastlink.ca> wrote:

> On 11-10-13 02:08 AM, Leif Roar Moldskred wrote:
> > Gene Wirchenko <genew@ocis.net> wrote:
> >>
> >> Sure there was.  It had an assumption about how much oomph the 
> >> rocket had.  The Ariane 5 had way more than the 4 did.  With the 
> >> 4, the overflow was not possible.  With the 5, it was.
> > 
> > Yes, but as the code wasn't written to be used on the Ariane 5, 
> > that was a valid assumption and not an error. The code was correct 
> > and fit for its intended use. That someone later took this code and 
> > tried to use it for something it was never meant to be used for is 
> > not an error in the code: A wrench makes a poor hammer, but that 
> > doesn't mean the wrench is constructed badly.
> > 
> When I read the report that Martin pointed us at, particularly pages 
> 4-6 (pages 8-10 of the PDF), I sure don't get the impression that the 
> code was "correct and fit for its intended use". This includes in a 
> wider sense the documentation that describes the assumptions and 
> decisions related to the code.
> 
> How do you know that the code was not meant to be used for the Ariane 
> 5? They _did_ use it for the Ariane 5; that's enough evidence for me 
> that they intended for it to be used not just for the Ariane 4 but 
> also for the Ariane 5. The report clearly states that the reasoning 
> related to the horizontal bias variable BH was *faulty* - they just 
> happened to be fortunate with Ariane 4. It was not, as you suggest, a 
> "valid assumption". And the follow-up exception-handling was 
> described as a systematic software design error.

I inferred that BH was left unprotected to reduce delay in the "event of 
a hold in the count-down," a feature used in Ariane 4. "The same 
requirement does not apply to Ariane 5." The "systematic software design 
error" was a culture of "only addressing random hardware failures." The 
management error was in not thoroughly testing the reused software.
 
> In a wider sense, if you've got a codebase that was intended for 
> situation A (or more precisely, since "intended" is a strong 
> purposeful word that implies knowing what you're about, "used with"), 
> and now you adopt it for situation B, that codebase _belongs_ to 
> situation B. You can't say it's fit and correct just because it still 
> works in situation A - who cares, actually? If it's unfit for 
> situation B it's unfit for situation B. Period.

A Java analogy might be adopting a 10 year old external dependency 
without running _all_ unit tests.

"No reference to justification of [the BH] decision was found directly 
in the source code." I can't help but think that generated documentation 
(e.g javadoc, adahtml) is one way to mitigate this kind of risk.

-- 
John B. Matthews
trashgod at gmail dot com
<http://sites.google.com/site/drjohnbmatthews>

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in praise of type checking Roedy Green <see_website@mindprod.com.invalid> - 2011-10-05 23:33 -0700
  Re: in praise of type checking Lew <lewbloch@gmail.com> - 2011-10-06 06:43 -0700
    Re: in praise of type checking Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2011-10-06 09:52 -0700
    Re: in praise of type checking Roedy Green <see_website@mindprod.com.invalid> - 2011-10-07 12:43 -0700
      Re: in praise of type checking Gene Wirchenko <genew@ocis.net> - 2011-10-07 14:57 -0700
      Re: in praise of type checking Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-10-07 20:18 -0400
  Re: in praise of type checking Robert Klemme <shortcutter@googlemail.com> - 2011-10-06 22:31 +0200
    Re: in praise of type checking Roedy Green <see_website@mindprod.com.invalid> - 2011-10-07 12:36 -0700
      Re: in praise of type checking Robert Klemme <shortcutter@googlemail.com> - 2011-10-08 16:05 +0200
        Re: in praise of type checking Lew <lewbloch@gmail.com> - 2011-10-08 09:35 -0700
          Re: in praise of type checking Robert Klemme <shortcutter@googlemail.com> - 2011-10-11 07:48 +0200
            Re: in praise of type checking Gene Wirchenko <genew@ocis.net> - 2011-10-11 13:04 -0700
            Re: in praise of type checking Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-10-11 17:52 -0300
              Re: in praise of type checking Patricia Shanahan <pats@acm.org> - 2011-10-12 01:49 +0100
                Re: in praise of type checking Gene Wirchenko <genew@ocis.net> - 2011-10-11 19:12 -0700
            Re: in praise of type checking Lew <lewbloch@gmail.com> - 2011-10-11 19:10 -0700
  Re: in praise of type checking Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-10-06 20:29 -0400
    Re: in praise of type checking Robert Klemme <shortcutter@googlemail.com> - 2011-10-06 23:56 -0700
      Re: in praise of type checking Gunter Herrmann <notformail0106@earthlink.net> - 2011-10-07 13:57 -0400
  Re: in praise of type checking Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-10-07 07:19 -0300
    Re: in praise of type checking Roedy Green <see_website@mindprod.com.invalid> - 2011-10-07 12:39 -0700
      Re: in praise of type checking Gene Wirchenko <genew@ocis.net> - 2011-10-07 15:03 -0700
        Space probes was Re: in praise of type checking Tom Anderson <twic@urchin.earth.li> - 2011-10-11 19:26 +0100
          Re: Space probes was Re: in praise of type checking Leif Roar Moldskred <leifm@dimnakorr.com> - 2011-10-12 01:15 -0500
            Re: Space probes was Re: in praise of type checking Travers Naran <tnaran@gmail.com> - 2011-10-12 07:23 -0700
            Re: Space probes was Re: in praise of type checking Martin Gregorie <martin@address-in-sig.invalid> - 2011-10-12 20:04 +0000
            Re: Space probes was Re: in praise of type checking Gene Wirchenko <genew@ocis.net> - 2011-10-12 13:53 -0700
              Re: Space probes was Re: in praise of type checking Leif Roar Moldskred <leifm@dimnakorr.com> - 2011-10-12 16:55 -0500
                Re: Space probes was Re: in praise of type checking Gene Wirchenko <genew@ocis.net> - 2011-10-12 15:02 -0700
                Re: Space probes was Re: in praise of type checking Leif Roar Moldskred <leifm@dimnakorr.com> - 2011-10-13 00:08 -0500
                Re: Space probes was Re: in praise of type checking Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-10-13 07:48 -0300
                Re: Space probes was Re: in praise of type checking "John B. Matthews" <nospam@nospam.invalid> - 2011-10-14 07:09 -0400
                Re: Space probes was Re: in praise of type checking Martin Gregorie <martin@address-in-sig.invalid> - 2011-10-12 22:03 +0000
            Re: Space probes was Re: in praise of type checking Tom Anderson <twic@urchin.earth.li> - 2011-10-14 14:14 +0100
  Re: in praise of type checking RedGrittyBrick <RedGrittyBrick@spamweary.invalid> - 2011-10-07 11:50 +0100
    Re: in praise of [loosey goosey] type checking) RedGrittyBrick <RedGrittyBrick@spamweary.invalid> - 2011-10-07 12:20 +0100
  Re: in praise of type checking Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-10-07 14:00 +0000

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