Bug 138562 Splite extendsexcpetion to seperate sub class
The suggestion is Parent invalid Cycle extends Different type extends Not top level extends
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/DesignElement.java
* @return the list of the errors found in validation, each of which is the
	 *         <code>SemanticException</code> object.
	 */
	public List validate( Module module )
	{
		errors = new ArrayList( );
		
		errors.addAll( UnsupportedElementValidator.getInstance( ).validate(
				module, this ) );
		
		
		
		
		
		
		
		
		
		
		
		
		ArrayList propMasks = (ArrayList) getLocalProperty( module,
				PROPERTY_MASKS_PROP );
		if ( propMasks != null )
		{
			ListIterator masks = propMasks.listIterator( );
			while ( masks.hasNext( ) )
			{
				PropertyMask mask = (PropertyMask) masks.next( );
				errors.addAll( mask.validate( module, this ) );