public function setLaunchURL($launchURL)
    {
        /*
         * TODO validate the actual URL?
         */
        if (empty((string) $launchURL)) {
            throw new ConfigurationException(
                'The configuration must specify a valid launch URL for the Tool Provider.',
                ConfigurationException::TOOL_PROVIDER
            );
        } else {
            $this->launchURL = (string) $launchURL;
        }
    }