Models and Data Binding

Data binding is used to bind two data or information sources together to keep them in sync. If data binding is implemented and defined properly, all changes in one data source are automatically reflected in the other data source. Usually, the UI uses data binding to bind UI controls to a data source that holds the application data, so that the controls are updated automatically whenever application data is changed.

To achieve this, there is a model and a data binding. The model instance holds the data and provides methods to set the data or to retrieve data from a server. It also provides a method for creating bindings to the data. When this method is called, a data binding instance is created, which contains the binding information and provides an event, which is fired whenever the bound data is changed. An element can listen to this event and update its visualization according to the new data.

The term data binding is also used when changes in the control cause updates in the underlying application data, such as data being entered by a user. This is called bi-directional binding or two-way binding.

A Web application should support several data sources, such as JSON, XML, Atom, or OData. However, the way in which data binding is defined and implemented within the UI controls should be independent of the respective data source. It should also be possible to create a custom model implementation for data sources that are not yet covered by the framework or are domain-specific.