Sunday, February 18, 2007

Excellent Article from Martin Fowler: Application Facades

There is a lot of good content up at Martin Fowler: Articles. (I definitely have to improve my reading speed …)

Today I read the Article about Application Facades. This is an excellent article!

The main goal of the article is to provide an example how to present a domain model in a GUI. Fowler uses an Application Facade to expose the domain model. The application facade then also defines a clear interface to test the business logic.

The article seems to be quite old. Fowler mentions problems with Café’s debugger (I vaguely remember something called Café, but I think I was playing SimCity in monochrome mode at that time…). Also Unit-Testing-Frameworks seemed not to exist at the time the article was written, since Fowler shows how to create a crude Framework by hand.

Nevertheless the article is very interesting and the Application Facade is a Pattern that can be used in modern business applications.

But the main value of the article is not the explanation of the pattern nor the code examples. What makes this article a real must read is how Fowler shows the process of developing a domain model. It is a real pleasure to see how the model is evolving in several iterations, and how OO-Techniques are applied to make the model more elegant. Fowler also shows the typical TDD-cycles of implementing-testing-extending-testing-refactoring… and it really makes sense!

I can really recommend this article for anybody who wants to see a beautiful example of DDD and applying OO-Techniques to a domain model.

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