Bug 183918 get relative file path of linkage library
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/command/ComplexPropertyCommand.java
* element, then the list is <strong>copied </strong> onto this element, and
	 * the new element is then appended to the copy.</li>
	 * </ul>
	 * 
	 * @param prop
	 *            the property definition whose type is list
	 * @param item
	 *            the item to add to the list
	 * @throws PropertyValueException
	 *             if the item to add is invalid.
	 */
	public void addItem( ElementPropertyDefn prop, Object item )
			throws PropertyValueException
	{
		assert prop != null;
		checkAllowedOperation( );
		if ( item == null )
			return;
		
		
		assert !( item instanceof IStructure );
		assertExtendedElement( module, element, prop );
		
		checkListProperty( prop );
		Object value = checkItem( prop, item );
		
		
		List list = element.getListProperty( module, prop.getName( ) );
		element.checkSimpleList( module, prop, list, value );
		ActivityStack stack = getActivityStack( );