- From: Dan Connolly <connolly@w3.org>
- Date: Fri, 18 May 2001 11:47:22 -0500
- To: Graham Klyne <Graham.Klyne@Baltimore.com>
- CC: rdf core <w3c-rdfcore-wg@w3.org>
Graham Klyne wrote: > > At 10:42 PM 5/17/01 -0500, Dan Connolly wrote: > >I'd appreciate it if anybody who *doesn't* know XML schema > >would take a look at this stuff and tell me if you're able > >to make sense of it. > > The first example (RDF0) seems straightforward. > > The second (RDF1), I think I see the pattern but am not completely sure: > > <element name="typedNode" abstract="true" type="rdf:typedNodeType"/> > > Seems to introduce a type, defined below, for element name > "typedNode". Being abstract, it can't be used directly, but forms a > template for instantiations that can: > > <element name="Description" type="rdf:typedNodeType" > substitutionGroup="rdf:typedNode"/> > > Thus, by this schema, only <Description> elements can appear in <RDF>? Yes, you've got it. If you want to be able to use other elements in <RDF>, you have to declare them similarly. If you follow the link to the Aug 2000 materials, you'll find a considerably more complete XML Schema for RDF (though it's based on an outdated version of XML Schema): ============= http://www.w3.org/2000/07/DAML-0-5-syntax <!-- so much for syntax structure. Now for the particular properties and classes... --> <element name="Statement" type="rdf:typedNodeType" equivClass="rdf:typedNode" /> <element name="Property" type="rdf:typedNodeType" equivClass="rdf:typedNode" /> ============= So yes, if you want to check your RDF document using XML Schema technology, you have to have declarations for all the classes, properties, etc. that you want to use. We need one for dublin core, one for DAML, etc. etc.; the good news is (a) they're easy to make; we might even be able to automate the translation from RDF schema to XML Schema (and/or the other way around) and (b) the benefit of providing an XML Schema is that it helps you find typos; e.g. if you write dc:author in stead of dc:creator, there's nothing wrong with that from an RDF schema perspective, but checking it with XML Schema technology flags it as an undeclared element. Actually, I suppose there are ways to use RDF schema to find such typos; TimBL has been hacking in that direction. And there are ways to describe RDF syntax with a less constraining XML Schema that would allow more stuff to go undeclared, but wouldn't find errors. This is just one approach. -- Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Friday, 18 May 2001 12:47:35 UTC