The revised syntax 
http://www.w3.org/TR/2004/REC-rdf-syntax-grammar-20040210/
says under "URI", 
"""If ·namespace-name· is present, set to a string value of the concatenation of 
the value of the ·namespace-name· accessor and the value of the ·local-name· 
accessor. Otherwise if ·local-name· is ID, about, resource, parseType or type, 
set to a string value of the concatenation of the ·RDF namespace URI reference·  
and the value of the ·local-name· accessor. Other non-namespaced ·local-name· 
accessor values are forbidden""".

Test file: http://www.w3.org/2006/03/wn/wn20/instances/wordsense-bank-noun-1.rdf

Currently the tabulator makes a bogus bode <nullabout> from an 'about' 
attribute. It should give a warning, but treat it as rdf:about.

Funny that there is no test in the RDF posistive parser tests which would have 
caught this?