CSS is an external file that specifies how your document should look; RDF-EASE is an external file that specifies what your document means.

…

.vcard
{
-rdf-typeof: "foaf:Person";
}
.vcard .fn
{
-rdf-property: "foaf:name";
-rdf-datatype: "xsd:string";
}
.vcard .url
{
-rdf-rel: "foaf:page";
}
/* This scopes everything within the hCard as applying to the
* hCard as a whole.
*/
.vcard, .vcard *
{
-rdf-about: nearest-ancestor(".vcard");
}

<div class="vcard"><a class="fn url" href="http://example.com">Joe Bloggs</a></div>
<div class="vcard"><span class="fn"><a class="url" href="http://example.com">Joe Bloggs</a></span></div>
<div class="vcard"><a class="url" href="http://example.com"><span class="fn">Joe Bloggs</span></a></div>

Now, that’s an intriguing idea — which could of course also be applied to Topic Maps.