Would you consider adding a removeAll method on ModelData interface?
Currently I am binding an final instance of a model to a form. When user is editing a particular item from the list I copy all of the properties from the list item to the model in the form. The only way to do this at the moment is to iterate through form model and remove each property. After that I can then use ModelData.setProperties().
The reason I'm doing the above is that I have a binding between Model and widgets in the form. So that when model changes the widget render changes and vice versa. I'm fairly new to GWT so let me know if you can see a better way of doing this.