Something to ponder :
One of the differences between building
architecture and software architecture is
that a lot of decisions about a building
are hard to change. It is hard to go back
and change your basement, though it is
possible.
There is no theoretical reason that anything
is hard to change about software.
If you pick any one aspect of software
then you can make it easy to change,
but we don’t know how to make everything
easy to change. Making something
easy to change makes the overall system
a little more complex, and making
everything easy to change makes the entire
system very complex. Complexity is
what makes software hard to change.