function serializeContentClassAttribute( $classAttribute, $attributeNode, $attributeParametersNode )
    {
        $defaultZoneLayout = $classAttribute->attribute( self::DEFAULT_ZONE_LAYOUT_FIELD );
        $dom = $attributeParametersNode->ownerDocument;

        $defaultLayoutNode = $dom->createElement( 'default-layout' );
        $defaultLayoutNode->appendChild( $dom->createTextNode( $defaultZoneLayout ) );
        $attributeParametersNode->appendChild( $defaultLayoutNode );
    }