/** Adds a sort specification
	 * @param string $path the path to sort by
	 * @param string $direction 'ASC' or 'DESC'
	 * @throws PntReflectionError if the path does not exist from >>itemType
	 */
	function addSortSpec($path, $direction='ASC') {
		$filter = PntSqlFilter::getInstance($this->itemType, $path);
		$filter->comparatorId = ($direction == 'DESC' ? '>' : '<');
		$this->addSortSpecFilter($filter);
	}