One for the FAQs, from Jeen on swig list:
rdf:about is not an actual property, but is simply a bit of syntax in
the RDF/XML serialization that is used to denote the subject of a
triple. It does not occur in the RDF graph and can not be queried
through SPARQL (or any other RDF query language that I know of).
The 'rdf:about' attribute is not a property, it just denotes that
"myCar" is the subject of the RDF triple (:myCar ex:hasColor "red").
Graham provides the spec refs.[Danny]