Weblog Without Honor or Humanity

Good software design contradicts eXtreme Programming.

I’ve been thinking lately about good software design. It occurred to me that good
design might contradict one of the
XP principles:
do the simplest thing possible. The problem is that good design is rarely
the simplest thing that will work. Let me give you an example: I’ve been
thinking about writing a GUI interface to CVS (yes, I know there’s plenty of
them; mine, you see, would be different in that it would be well designed).

One rule of good design is that software should anticipate user’s actions. CVS
viewer is useless until you define at least one CVS repository to access
(i.e. provide repository host, port number, username and password). Obviously
none is defined when you use the program for the first time so when used for the
first time software should present a user with a dialog that asks for CVS
repository information (host, port, username, password) and a visible link to help file that explains in detail the
meaning of options.

It mustn’t be so obvious because none of the existing  CVS
viewers do that, they all start with the same blank, generic screen. But
there’s more: it’s reasonably to expect that user already has some CVS
repositories on his hard-drive that he created using command-line tool. So an
option to scan a hard-drive looking for those repositories and add them
automatically to the program would be nice (again, I don’t think any existing
program offers that). If you ever had to wait for any program to scan the whole
hard-drive, you know one thing: it takes an awful lot of time. So the program
should offer a way to cancel (and/or pause) this operation. The simplest way to
implement such feature is to scan the hard-drive in whatever order is most
convenient for your OS/library. However this is rarely the most
convenient way for the user: there are directories like
c:\windows or c:\Program Files that are big (i.e. many
files -> take a lot of time to scan) but are unlikely to contain those
repositories so you could improve the feature by intelligently deciding which
directories to scan first. So we have a direct conflict: XP wants the simplest
thing possible, good design wants the best thing possible.

I’m not claiming that this conflict is present all the time but I think it
happens more often than not.