public function addOrderByColumn($directionalColumnName) {
     list($columnName, $isSortAscending) = ColumnBasedComparator_AbstractSortingConfiguration::parseDirectionalColumnName($directionalColumnName);
     $this->addSortingConfiguration($this->initiateSortingConfiguration($columnName, $isSortAscending));
 }
    protected static function mapOrderBy(array $parsedUIMetaDataNames, array $columnMappings, array $orderBy = NULL, $isMeasureMapped) {
        $mappedOrderBy = NULL;

        if (isset($orderBy)) {
            foreach ($orderBy as $key => $directionalColumnName) {
                list($columnName, $isSortAscending) = ColumnBasedComparator_AbstractSortingConfiguration::parseDirectionalColumnName($directionalColumnName);
                $parsedUIMetaDataName = $parsedUIMetaDataNames[$columnName];

                if (self::isColumnMappable($parsedUIMetaDataName, TRUE, $isMeasureMapped)) {
                    $mappedOrderBy[$key] = ColumnBasedComparator_AbstractSortingConfiguration::assembleDirectionalColumnName($columnMappings[$columnName], $isSortAscending);
                }
            }
        }

        return $mappedOrderBy;
    }