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docs/guide.data-binding.ngdoc

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+@workInProgress
+@ngdoc overview
+@name Developer Guide: Data Binding
+@description
+
+# Data Binding
+
+Data-binding allows you to treat the model as the single-source-of-truth of your application, and
+consider the view as only a projection of the model, at all times. The process of copying the model
+values to the view, and any changes to the view by the user to the model, is known as data-binding.
+
+## Classical Template Systems
+
+<img class="right" src="img/One_Way_Data_Binding.png"/>
+At the highest level, angular looks like a just another templating system. But there is one
+important reason why angular templating system is different and makes it very good fit for
+application development: two-way data binding.
+
+Most templating systems bind data in only one direction: they merge a template and model together
+into a view, as illustrated in the diagram to the right. After the merge occurs, any changes to
+the model or in related sections of the view are NOT automatically reflected in the view. Worse,
+any changes that the user makes to the view are not reflected in the model. This means that the
+developer has to write code that constantly syncs the view with the model and the model with the
+view.
+
+
+# angular Template Systems
+<img class="right" src="img/Two_Way_Data_Binding.png"/>
+The way angular templates works is different, as illustrated in the diagram on the right. They are
+different because first the template (which is the uncompiled HTML along with any additional markup
+or directives) is compiled on the browser, and second, the compilation step produces a live view.
+We say live because any changes to the view are immediately reflected in the model, and any changes
+in the model are propagated to the view. This makes the model always the single-source-of-truth for
+the application state, greatly simplifying the programing model for the developer. You can think of
+the view as simply an instant projection of your model.
+
+Because the view is just a projection of the model, the controller is completely separated from the
+view and unaware of it. This makes testing a snap because it is easy to test your controller in
+isolation without the view and the related DOM/browser dependency.
+
+For details about how data binding works in angular, see {@link angular.scope Scope}.