On Thu, May 14, 2009 at 2:54 PM, Philip Taylor <excors+wha...@gmail.com> wrote: > [...] > <urn:subject> <urn:predicate> _:X . > [...] > <div item> > <link itemprop="about" href="urn:subject"> > <meta itemprop="urn:predicate" item id="X"> > </div> > [...] > So, I can't see any limits on expressivity other than that literals > must be strings.
Hmm, I think I'm wrong here. 'id' has to be unique, which means this pattern won't work if _:X is the object for triples with two different subjects. Additionally, there must be a chain from every blank node back to <> via <http://www.w3.org/1999/xhtml/vocab#item>, else it won't get serialised (since serialisation starts from top-level items and recurses down the correspondence chains). As a consequence of this and the previous point, it is impossible to express cycles (e.g. "_:X <urn:predicate> _:X", or any longer cycles) unless the cycle contains <>. So there are these two restrictions on the shapes of expressible RDF graphs. (I can't think of any other restrictions, though...) -- Philip Taylor exc...@gmail.com