function definition() {
        global $USER;

        $mform    = $this->_form;
        $mform->setDisableShortforms(true);

        $mform->addElement('header', 'searchbyusername', get_string('searchbyusername'), '');

        $purpose = user_edit_map_field_purpose($USER->id, 'username');
        $mform->addElement('text', 'username', get_string('username'), 'size="20"' . $purpose);
        $mform->setType('username', PARAM_RAW);

        $submitlabel = get_string('search');
        $mform->addElement('submit', 'submitbuttonusername', $submitlabel);

        $mform->addElement('header', 'searchbyemail', get_string('searchbyemail'), '');

        $purpose = user_edit_map_field_purpose($USER->id, 'email');
        $mform->addElement('text', 'email', get_string('email'), 'maxlength="100" size="30"' . $purpose);
        $mform->setType('email', PARAM_RAW_TRIMMED);

        $submitlabel = get_string('search');
        $mform->addElement('submit', 'submitbuttonemail', $submitlabel);
    }