[RDFa] ISSUE-3: syntactic sugar for rdf:type

Hi all,

In today's telecon, we proposed and resolved to use a *new* attribute,
rather than @class or @role, for the rdf:type syntactic sugar. Thus,
@class and @role do not currently result in any triples being generated,
although one may consider that they will in a future version.

The question, then, is which attribute to use. Steven expressed
reservations about two-word attributes like "isa" or "instanceof", and
instead proposed: denotes, depicts, represents, category, ilk, kind.

Other thoughts?

I'm partial to "instanceof" and "kind", and I have no additional
suggestions.

-Ben