The point is, anyway, that enabling something like SMW (probably with fewer features) is orthogonal to RDFa/microdata/RDF support -- the extension could incidentally output RDF or whatnot, but it doesn't matter for internal use.
Perhaps the right approach for us would be to have "some" syntax for providing this info, and then generating html5 microdata and/or rdfa into the rendered html, write the triple into a smw backend store, and provide rdf/xml/n3/whatever output via the api.
there are three aspects here: specify, store, output. perhaps we should look at them separately.
-- daniel