Normativity of role taxonomy

The section on role taxonomy is marked normative, but it is entirely  
unclear what it means for the taxonomy to be normative--particularly  
when parts of the taxonomy are only a conceptual aid and aren't even  
allowed to appear in content.

Please clarify what is meant of make the taxonomy modeling informative.

-- 
Henri Sivonen
hsivonen@iki.fi
http://hsivonen.iki.fi/