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
String displayLabel = module.getMessage( getDisplayNameID( ) );
		if ( StringUtil.isBlank( displayLabel ) )
		{
			displayLabel = getDisplayName( );
		}
		if ( StringUtil.isBlank( displayLabel ) )
		{
			displayLabel = getNameForDisplayLabel( );
		}
		if ( level == USER_LABEL )
		{
			return displayLabel;
		}
		MetaDataDictionary dictionary = MetaDataDictionary.getInstance( );
		IElementDefn elementDefn = dictionary.getElement( getElementName( ) );
		if ( StringUtil.isBlank( displayLabel ) )
		{
			displayLabel = elementDefn.getDisplayName( );
		}
		if ( StringUtil.isBlank( displayLabel ) )
		{
			displayLabel = elementDefn.getName( );
		}
		return displayLabel;
	}
	/**
	 * Returns the name of this element for display label.
	 * 
	 * @return the name of this element for display label.
	 */