Domain Driven Design In a Nutshell

If you know anything about domain driven design, you know that the domain is the heart of your application. It is the warm little centre that the life of your project crowds around.

Jeff Palermo is the man. Jeff eloquently explained on DotNetRocks that he has a problem with layered architectures. Each layer talks only to the layer below it and so forth. This is the traditionalist view of a system architecture. Jeff likes to think of a system's architecture like an onion. At the core of the onion is the domain model. The layers around the domain model provide more functionality. This extra functionality can include persistence, reporting, aggregating concepts into different forms and much more. The outer most layers of the onion deal with human interaction. The outer most layer of an application could be a command window, windows form, web app, the buttons on a toaster. The neat thing is that if you peel away all the layers of the onion you are left with the domain model. In my opinion the domain model is king. Whenever, I have a new story to work on I focus on the domain first, then the UI and lastly everything in between.

(It kind of looks like an onion, but it most likely is crop circle.)