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/observable/map/ObservableMap.java
public boolean isStale() {
		return stale;
	}
	/**
	 * @param stale
	 *            The stale state to set. This will fire a stale event if the
	 *            given boolean is true and this observable set was not already
	 *            stale.
	 */
	public void setStale(boolean stale) {
		boolean wasStale = this.stale;
		this.stale = stale;
		if (!wasStale && stale) {
			fireStale();
		}
	}
	public Object put(Object key, Object value) {
		throw new UnsupportedOperationException();
	}
	public Object remove(Object key) {
		throw new UnsupportedOperationException();
	}
	public void clear() {
		throw new UnsupportedOperationException();
	}
	public void putAll(Map arg0) {
		throw new UnsupportedOperationException();
	}
}