protected function _validateString($value, $column) {
        $value = is_string($value) ? trim($value) : $value;
        if (empty($value) && $value !== '0') {
            throw new Garp_Model_Validator_Exception(
                sprintf(__('%s is a required field'), __(Garp_Util_String::underscoredToReadable($column)))
            );
        }
    }