protected function _checkType( $value )
	{
		switch( $value )
		{
			case MShop_Order_Item_Base_Address_Abstract::TYPE_DELIVERY:
			case MShop_Order_Item_Base_Address_Abstract::TYPE_PAYMENT:
				return;
			default:
				throw new MShop_Order_Exception( sprintf( 'Service of type "%1$s" not available', $value ) );
		}
	}