- From: Dan Connolly <connolly@w3.org>
- Date: 15 Feb 2002 13:33:28 -0600
- To: "Smith, Michael K" <michael.smith@eds.com>
- Cc: Pat Hayes <phayes@ai.uwf.edu>, "Peter F. "Patel-Schneider <pfps@research.bell-labs.com>, www-webont-wg@w3.org
On Fri, 2002-02-15 at 12:18, Smith, Michael K wrote: > Dan, > > Sure, there are various places where the triple syntax is defined. And the > model theory uses it. Which is appropriate, the model theory should be > using an abstract syntax. But in neither case is this defined to be the > syntax of RDF. There is a chapter called > > 6. Formal Grammar for RDF > > which I take to be the syntax of RDF. And it has many advantages over the > section you point to. Has it been demonstrated that the description in > section 5 admits all and only the triples that are implied by the formal > grammar of section 6? In practice, yes. The various RDF parser APIs generally just emit triples (or: allow access to triples). So in practice, if you use RDF tools, you get all and only the triples from section 6 of the spec. In fine technical detail, there are some issues. For example, a property could be named http://vocab/bad-name/ and there's no way to break that into a namespace name and a localname ala... <bad-name/ xmlns="http://vocab/"/> since / isn't allowed in an XML name. There are various limitations of this sort in the RDF/xml syntax. These are acknowledged in the RDF issues list, e.g. http://www.w3.org/2000/03/rdf-tracking/#rdfms-syntax-incomplete and explained in recent RDF syntax drafts. 6 Serialising an RDF Graph to RDF/XML It is not possible for all graphs that can be expressed in the RDF Model Theory ([RDF-MODEL]) to be encoded in this syntax. http://www.w3.org/TR/2001/WD-rdf-syntax-grammar-20011218/#section-Serialising > Again, the wording in section 5 talks about the requirement that "the > elements of Ord must be used in sequence starting with RDF:_1". But we have > an open world. What does it mean if I don't find RDF:_2, but I have RDF:_3? > As far as I can tell, it means nothing other than that I may not be looking > everywhere I need to. Right; the RDF Core WG decided this is a bug in the spec; cf http://www.w3.org/2000/03/rdf-tracking/#rdf-containers-formalmodel it's not in the recent model theory/syntax specs. > The RDF:LI syntax of section 6 seems much easier to both present and reason > about. Though I confess I still don't know what the following means, in that > I don't know what the first element of the sequence is. > > <rdf:Seq ID="pages"> > <rdf:li resource="http://foo.org/foo.html" /> > <rdf:li resource="http://bar.org/bar.html" /> > </rdf:Seq> > <rdf:Seq about="#pages"> > <rdf:li resource="http://foo.org/bim.html" /> > </rdf:Seq> > > Or maybe this is not permissible. It's not a syntax error. You'll get both pages rdf:_1 foo and pages rdf:_1 bim I would probably conclude that foo=bim, but I'm not sure if the specs say that. I'd have to double-check. -- Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Friday, 15 February 2002 14:33:16 UTC