protected function validate($params=array()) {
        foreach ($params as $key=>$value) {
            $this->comment_param->$key = $value;
        }
        $validation = plugin_callback($this->plugintype, $this->pluginname, 'comment', 'validate', array($this->comment_param), false);
        if (!$validation) {
            throw new comment_exception('invalidcommentparam');
        }
    }