Re: Re[2]: The Cost of Change Curve

From: "Doug Swartz" <daswartz.at.prodigy.net <at> yahoogroups.at.jhrothjr.com>
To: "Robert C. Martin"
<extremeprogramming.at.yahoogroups.com <at> yahoogroups.at.jhrothjr.com>
Sent: Thursday, April 01, 2004 8:16 AM
Subject: Re[2]: [XP] The Cost of Change Curve

>
> Wednesday, March 31, 2004, 11:04:36 PM, Robert C. Martin wrote:
>
> > Some folks have said that XP flattens the curve.  I don't think that's
true.
> > I think that whatever flattening has taken place has been because of
things
> > that are outside of XP's control.  I think XP works *because* of this
> > flattening; I don't think XP causes the flattening.
>
> > What agency might have caused the flattening?  Consider:
>
> > The cost of change curve was measured by Boehm thirty years ago.  Since
that
> > time:
> >   * Computers are 1000 time faster.
> >   * Computers have 1000 times as much iternal storage.
> >   * Computers have 1000 times as much external storage.
> >   * Computers are 1000 times smaller by volume
>
> > That's 12 (count them: TWELVE) orders of magnitude difference; and if we
> > looked we could probably find three or four more.  What difference do
these
> > twelve zeros make?
>
> > I don't have to wait overnight to compile a 1000 line program; instead I
can
> > run hundreds of compiles every day.
>
> > Every developer can have one or more of these 1,000,000,000X machines
for
> > their own private use instead of sharing it with the whole department.
>
> > These powerful machines support *tools* that help you edit your code,
> > refactor your code, compile your code, test your code, package your
code,
> > deploy your code.
>
> And XP and the other Agile approaches take advantage of these
> environmental changes. It's, at least partly, a case of the
> difference between a "culture of plenty" and a "culture of
> scarcity". In our culture of plenty we tend to do things much
> differently.
>
> Therefore, I think I agree with Uncle Bob, that flattening the
> change curve is the result of the practices we do. But the
> practices wouldn't have been possible 35 years ago.

In a sense that's true, but it's not a matter of scale, it's a
matter that the increase in availible computing power lets
us do something completely different with it. 35 years ago,
when you could only get one compile and test run a day
with your tray of punched cards, it made a great deal of sense
to do thorough requirements analysis up front, followed by a
complete design and only then go to code.

The fact is that it's not the amount of computing horsepower,
it's how it's applied. I could have done TDD on my Apple II
25 years ago, for instance. I could have done TDD on my
IBM mainframe using TSO 30 years ago if I'd had the tools
availible.

John Roth

>
>
>
> -- 
>
>  Doug Swartz
>  daswartz <at> prodigy.net
>
>
>
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