Application Layer vs UI

Question

Greetings ye ol whimsical denizens of truthful knowledge,

Got a quickie for ya'll:

I'm wondering if the Application Layer is analogus with the UI Layer, generally ?

I'm reading Evans DDD book and he keeps referring to the Application Layer, but doesn't mention the UI explicitly, and so I'm left to wonder.

Could someone please help me make this distinction ? Thanks.

Answer 1

The application layer contains the application behavior, i.e. what happens when the user clicks somewhere. In front of the application layer there is often a presentation layer which defines the look-and-feel of the application and specific GUI widgets used. Together, these form the UI.

domain <- application <- presentation

DDD is mostly concerned with the domain layer and a forming a ubiquitous model/language. It is usually not concerned with how layers are defined, except that non-domain concepts are kept out of the domain layer and in other layers such as the application layer.