public static function compare( core_kernel_classes_Container $o1,  core_kernel_classes_Container $o2)
    {
        $returnValue = (int) 0;

        
        if($o1 instanceof core_kernel_classes_Literal && $o2 instanceof core_kernel_classes_Literal) {
        	$returnValue = strcasecmp($o1->literal,$o2->literal);
        }
        else if($o1 instanceof core_kernel_classes_Resource && $o2 instanceof core_kernel_classes_Resource) {
        	$returnValue = strcasecmp($o1->getUri(),$o2->getUri());
        }
        else {
           	throw new common_Exception('try to compared not implemented type');
        }
        

        return (int) $returnValue;
    }