public function getValue(FedoraResource $res, array $transformations = []): string {
        $overwrite = filter_input(INPUT_GET, $this->getName());
        if ($overwrite !== null) {
            $valueProp = '';
            $default = $overwrite;
        } else {
            $meta      = $this->getMetadata();
            $default   = $meta->all(RC::get('fedoraServiceParamDefaultValueProp'));
            $default   = count($default) > 0 ? (string) $default[0] : '';
            $valueProp = $meta->all(RC::get('fedoraServiceParamRdfPropertyProp'));
            if (count($valueProp) > 0) {
                $valueProp = (string) $valueProp[0];
            } else {
                $valueProp = '';
            }
        }
        return self::value($res, $valueProp, $default, $transformations);
    }