" Hence the term architectural pattern may be useful (Buschmann, et al 1996), or perhaps an aggregate design pattern. Operation In broad terms, constructing an application using an MVC architecture involves defining three classes of modules . Model: This is the domain-specific representation of the information on which the application operates. The model is another name for the domain layer. Domain logic adds meaning to raw data e. g. calculating if today is the user's birthday or the totals, taxes and shipping charges for shopping cart items. Japanese Car Model View: This renders the model into a form suitable for interaction, typically a user interface element. MVC is often seen in web apps: the view is the html page and the code which gathers dynamic data for the page. "

", controller updates user's shopping cart) A view uses the model to generate an appropriate user interface (e. g. , view produces a screen listing the shopping cart contents). The view gets its own data from the model (or direct from the data access layer - sometimes there is no domain logic to do). The model should have no direct knowledge of the view. However, the observer pattern can be used to provide some indirection between model and view, allowing the model to notify interested parties of a change. A view object can register itself with the model and listen for changes but the model itself remains view-agnostic. Model Car Body The controller does not pass domain objects (the model) to the view although it might issue a command telling the view to update itself. The user interface waits for further user interactions, which begins the cycle anew. "