Bug 126839 [DataBinding] IObservable refactoring
bundles/org.eclipse.jface.databinding/src/org/eclipse/jface/internal/provisional/databinding/IBindingListener.java
/**
	 * Method bindingEvent.  The method that is called when something interesting
	 * occurs in the data flow pipeline.
	 * 
	 * @param e The IBindingEvent to handle.
	 * @return null if no error or an error message to abort the operation.  The
	 * error message will be propagated to the data binding context's error
	 * message updatable.
	 */
	public String bindingEvent(BindingEvent e);
	
}