I have always liked (and often written about) an alternative: for HTML: http://example.com/test.html, for semantic data: http://example.com/test.n3 (N3 RDF format).

If a web app creates dynamic data at URL: http://example.com/stockfeeds?symbol=APPL then perhaps use something like: http://example.com/stockfeeds.n3?symbol=APPL to get RDF. Also, have standard (or commonly used) meta data to point to an equivalent RDF URI in generated HTML.