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From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.cog-eng
Subject: Re: knowledge and design
Message-ID: <6176@utzoo.UUCP>
Date: Wed, 27-Nov-85 16:26:21 EST
Article-I.D.: utzoo.6176
Posted: Wed Nov 27 16:26:21 1985
Date-Received: Wed, 27-Nov-85 16:26:21 EST
References: <11800001@uiucme>
Organization: U of Toronto Zoology
Lines: 28

> Computer Science has learned what the rest of us are only just
> catching on to - complex systems require a disciplined, structured
> design approach unless you want to spend your life debugging.

Computer Science has not yet learned what the rest of us have known for
some time:  even disciplined, structured design approaches don't solve
all the problems.  Not even close.

> And in fact there are power plants and factories and ships and
> airplanes out there - all of them incredibly complex systems -
> that are still being debugged after ten, twenty, even thirty years
> of service.

This is also the case for most major programs, including the ones written
by computer scientists using structured design approaches.  Even the Holy
Writ of computer science's Provisional Wing (the mathematical-correctness-
solves-everything advocates), Dijkstra's book, which explicitly claims to
teach you how to write bug-free programs, has bugs in its examples.  Not
many bugs, but a few, and those examples are not large programs.


Now that I've offended all my Computer Science friends, I should point out
that there is much to be said for disciplined, structured design, and even
for mathematical correctness arguments, provided you regard them as useful
techniques rather than the Answer To Everything.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry