protected function define_structure() {

        $paths = array();
        $userinfo = $this->get_setting_value('userinfo');

        $area = new restore_path_element('grading_area', '/areas/area');
        $paths[] = $area;
        // attach local plugin stucture to $area element
        $this->add_plugin_structure('local', $area);

        $definition = new restore_path_element('grading_definition', '/areas/area/definitions/definition');
        $paths[] = $definition;
        $this->add_plugin_structure('gradingform', $definition);
        // attach local plugin stucture to $definition element
        $this->add_plugin_structure('local', $definition);


        if ($userinfo) {
            $instance = new restore_path_element('grading_instance',
                '/areas/area/definitions/definition/instances/instance');
            $paths[] = $instance;
            $this->add_plugin_structure('gradingform', $instance);
            // attach local plugin stucture to $intance element
            $this->add_plugin_structure('local', $instance);
        }

        return $paths;
    }