Design Patterns Explained: A New Perspective on Object-Oriented Design

In the Real World: Variations

In the real world, problems are not tidy or well behaved. Except in the most trivial problems, there always seem to be exceptions and variations that are not well organized. They are the “gotchas” that rise up to wreck our finely crafted models.

For example, patients coming to a hospital typically go to the admitting office first. But when there is a life-threatening situation, the patient goes directly to the emergency room before having to go to admitting. These are the variations in the real world, the different special cases that our system has to deal with.

And this is what creates headaches for us analysts. Can patterns help us deal with variation more efficiently?

I have used an approach to make explicit the ...