function image() {
        global $OUTPUT;

        $params = array('d'=>$this->data->id, 'fid'=>$this->field->id, 'mode'=>'display', 'sesskey'=>sesskey());
        $link = new moodle_url('/mod/data/field.php', $params);
        $str = '<a href="'.$link->out().'">';
        $str .= $OUTPUT->pix_icon('field/' . $this->type, $this->type, 'data');
        $str .= '</a>';
        return $str;
    }