Bug 126658 [CommonNavigator] [DND] Complete definition of DND API
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/dnd/CommonDropAdapterDescriptor.java
IConfigurationElement[] children = element
				.getChildren(TAG_DRAG_EXPRESSION);
		if (children.length == 1)
			dragExpr = new CustomAndExpression(children[0]);
		children = element.getChildren(TAG_DROP_EXPRESSION);
		if (children.length == 1)
			dropExpr = new CustomAndExpression(children[0]);
	}
	/**
	 * 
	 * @param anElement
	 *            The element from the set of elements being dragged.
	 * @return True if the element matches the drag expression from the
	 *         extension.
	 */
	public boolean isDragElementSupported(Object anElement) {
		if (dragExpr != null)
			try {
				return dragExpr
						.evaluate(new EvaluationContext(null, anElement)) == EvaluationResult.TRUE;
			} catch (CoreException e) {
				NavigatorPlugin.logError(0, e.getMessage(), e);
			}
		return false;
	}
	/**
	 * 
	 * @param anElement
	 *            The element from the set of elements benig dropped.
	 * @return True if the element matches the drop expression from the