Bug 118429 [DataBinding] Validation should use IStatus, not just Strings
In order to use data binding in Workbench or IDE dialogs and preference pages, we need validation in terms of IStatus objects. Using strings is too simplistic. For example, look at the wizard for creating a new class. You will get a warning if the class name does not start with an uppercase letter, or if you don't provide a package name, but you will still be able to click "Finish" to proceed anyway. (Note that IStatus is currently not on the classpath, we need to re-introduce the dependency on org.eclipse.equinox.common, which contains IStatus etc.)
bundles/org.eclipse.core.databinding/src/org/eclipse/core/databinding/BindingEvent.java
/**
	 * A constant indicating that this event is occuring during a partial
	 * validation event.
	 */
	public static final int EVENT_PARTIAL_VALIDATE = 2;
	/**
	 * A constant indicating that this event is occuring during an element
	 * remove operation.
	 */
	public static final int EVENT_REMOVE = 3;
	
	/**
	 * A constant indicating that this event is occuring during a lazy list
	 * insert operation.
	 */
	public static final int EVENT_LAZY_INSERT = 4;
	
	/**
	 * A constant indicating that this event is occuring during a lazy list
	 * delete operation.
	 */
	public static final int EVENT_LAZY_DELETE = 5;
	/**
	 * A constant indicating that this event is occuring immedately after the
	 * value to copy has been gotten from its IUpdatable.
	 */
	public static final int PIPELINE_AFTER_GET = 0;
	/**
	 * A constant indicating that this event is occuring immedately after the
	 * value has been validated as being possible to convert to the other