#Practical Object Oriented Design in Ruby
Design that anticipate specific future requirements almost always end badly.
Practical design does not anticipate what will happen to your application, it merely accepts that something
will and that, in the present, you cannot know what. It does not guess the future; it preserves your options for accommodating the future.
It doesn't choose; it leaves you room to move.
The purpose of design it to allow you to do it later and its primary goal is to reduce the cost of change.
Design is more the art of preserving changeability than it is the act of achieving perfection.