MVC

Model–view–controller  ( MVC ) is a software  architectural pattern  for implementing  user interfaces . It divides a given software application into three interconnected parts, so as to separate internal representations of information from the ways that information is presented to or accepted from the user.  The central component, the  model , consists of application data, business rules, logic and functions. A  view  can be any output representation of information, such as a chart or a diagram. Multiple views of the same information are possible, such as a bar chart for management and a tabular view for accountants. The third part, the  controller , accepts input and converts it to commands for the model or view.

In addition to dividing the application into three kinds of components, the model–view–controller design defines the interactions between them.

• A controller can send commands to the model to update the model's state (e.g., editing a document). It can also send commands to its associated view to change the view's presentation of the model (e.g., by scrolling through a document).
• A model notifies its associated views and controllers when there has been a change in its state. This notification allows the views to produce updated output, and the controllers to change the available set of commands. In some cases an MVC implementation might instead be "passive," so that other components must poll the model for updates rather than being notified.
• A view requests information from the model that it needs for generating an output representation to the user.

Although originally developed for desktop computing, model–view–controller has been widely adopted as an architecture for World Wide Web applications in major programming languages. Several commercial and noncommercial application frameworks have been created that enforce the pattern. These frameworks vary in their interpretations, mainly in the way that the MVC responsibilities are divided between the client and server.

Early web MVC frameworks took a thin client approach that placed almost the entire model, view and controller logic on the server. In this approach, the client sends either hyperlink requests or form input to the controller and then receives a complete and updated web page (or other document) from the view; the model exists entirely on the server.As client technologies have matured, frameworks such as JavaScriptMVC and Backbone have been created that allow the MVC components to execute partly on the client (see also AJAX).