What does the shipping_alias column do / its intended purpose?

	public function __construct( $config = array() ) {
		parent::__construct($config);
		$this->db = JFactory::getDBO();

		  // extra code
	}
	// to be called during the installation process, or the first time the plugin is being used
	private function initDB() {
		$this->addColumn('cart', 'cart_reminded', '`cart_reminded` tinyint(4) NOT NULL DEFAULT \'0\'');
		$this->addColumn('order', 'order_reminded', '`order_reminded` tinyint(4) NOT NULL DEFAULT \'0\'');

                // extra code
	}
	private function addColumn($table, $column, $type) {
		$tablename = '#__hikashop_'.$table;
		if(!HIKASHOP_J30) {
			$columnsTable = $this->db->getTableFields($tablename);
			$columns = reset($columnsTable);
		} else {
			$columns = $this->db->getTableColumns($tablename);
		}

		if(!isset($columns[$column])) {
			$databaseHelper = hikashop_get('helper.database');
			$databaseHelper->addColumns($table, $type);
		}
	}
	public function onHikashopBeforeCheckDB(&$createTable, &$custom_fields, &$structure, &$helper) {
		$structure['#__hikashop_cart']['cart_reminded'] = '`cart_reminded` tinyint(4) NOT NULL DEFAULT \'0\'';
		$structure['#__hikashop_order']['order_reminded'] = '`order_reminded` tinyint(4) NOT NULL DEFAULT \'0\'';
	}