Common methods should be defined via interface

[nbartels]

You can check the GWT Framework as inspiration. The Button object for example implements a lot of interfaces to allow the developer to work on a more abstract base.

http://www.gwtproject.org/javadoc/latest/com/google/gwt/user/client/ui/Button.html

So the interface work as marker for special functions and provide a unified method name to access this function.

For example:
The HasVisibility interface let the developer now, that the visibility of this component can be changed and the methods to do this are isVisible and setVisible(boolean).

Transforming this to RestFB we should provide interfaces like HasCreatedTime or HasComments. Objects with a createdTime field or a comments field can implement this interfaces. We have to provide these methods already but developers have to check the method list of an object. With the interface this is much faster accomplished because a fast check in the javadoc provides everything needed. Check the Button example.