new batch of docs

docs/content/guide/dev_guide.templates.databinding.ngdoc

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+@workInProgress
+@ngdoc overview
+@name Developer Guide: Templates: Data Binding in Angular
+@description
+
+
+Data-binding in angular web apps is the automatic syncing of data between the model and view
+components.  The way that angular implements data-binding lets you treat the model as the
+single-source-of-truth in your application.  The view is a projection of the model at all times.
+When the model changes, the view reflects the change, and vice versa.
+
+
+## Data Binding in Classical Template Systems
+
+
+<img class="right" src="img/One_Way_Data_Binding.png"/>
+Most templating systems bind data in only one direction: they merge template and model components
+together into a view, as illustrated in the diagram. After the merge occurs, changes to the model
+or 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.
+
+
+## Data Binding in Angular Templates
+
+
+<img class="right" src="img/Two_Way_Data_Binding.png"/>
+The way angular templates works is different, as illustrated in the diagram. 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.
+
+
+
+
+## Related Topics
+
+
+* {@link dev_guide.scopes Angular Scopes}
+* {@link dev_guide.templates Angular Templates}