TITLE: Software Design is a Bet on a Particular Future
AUTHOR: Eugene Wallingford
DATE: October 10, 2013  5:17 AM
DESC: 
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BODY:
This truth is expressed nicely by
<A HREF="http://raganwald.com/2013/10/08/defactoring.html">
   Reginald Braithwaite</A>:

<BLOCKQUOTE><EM>
 Software design is the act of making bets about the future.  A
 well-designed program is a bet on what will change in the future,
 and what will not change.  And a well-designed program communicates
 the nature of that bet by being relatively flexible about things
 that the designers think are most likely to change, and being
 relatively inflexible about the things the designers think are
 least likely to change.
</EM></BLOCKQUOTE>

That's what refactoring is all about, of course.  Sometimes, a
particular guess turns out to be wrong.  We have the wrong factors,
the wrong components, for adding a new feature.  So we change the
shape of the code -- we factor it into different components -- to
reflect our new best understanding of the future.  Then we move on.

Sometimes, though, there are forces that make more desirable a
relatively monolithic piece of code (or, as Braithwaite points out,
a system decomposed into relatively less flexible components).  In
these cases, we need to defactor, to use Braithwaite's term: we
recombine some or all of the parts to create a new design.

Predicting the future is hard, even for experienced programmers.
One of the goals of agile design is to not think too far ahead,
because that means committing to a future too far removed from
what we already know to be true about our program.
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