Software architecture

The organization of a software system's major components, their responsibilities and their interactions. A software architecture constrains which components own state and which may request or observe changes. Model-view-controller is one example for interactive applications.

Separate an application's domain state and rules into a model, its presentation into a view, and interpretation of user actions into a controller. The controller requests model operations; the view renders coherent model state. A playlist model, for example, owns song order independently of whether a menu, button or keyboard action requests a move. The Observer pattern often carries model-change notifications to views, but model-view-controller defines responsibilities rather than requiring a particular notification mechanism. This supports separation of concerns and testing domain logic independently of a graphical interface.