core attribute 'type' shows nothing for group or unit

["Tom Comerford" <tom@supratext.com>]

In the description for the core attribute ‘type’ (section 4.3.1.40), there’s no value description and no default value for <group> or <unit>. Also the ‘used in’ section doesn’t include these elements. However, they are referenced by those elements (section 4.2.2.4 group, section 4.2.2.5 unit).