W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > August 2001

Re: Reifying using XML attributes only

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Date: Thu, 30 Aug 2001 23:49:21 +0100
To: w3c-rdfcore-wg@w3.org
CC: Dan Connolly <connolly@w3.org>
Message-ID: <15776.999211761@tatooine.ilrt.bris.ac.uk>
>>>Dan Connolly said:
<snip/>
> Umm... I'm running into the same sort of use/mention issues
> here as are all over the RDF 1.0 spec.
> 
> The fact that both XML attributes and RDF properties have
> values is one source of confusion.
> 
> The values/objects of statements whose predicate is rdf:type are
> not constrained at all, as far as I know, let alone
> being constrained to a URI-reference.
> 
> i.e. it's not the case that
> 
> 	rdf:type rdfs:range xmlschema-datatype:URI-reference.
> 
> right?

I would say no.

I am describing the RDF/XML syntax as described in RDF M&S which does
not require or use RDF Schema or XML Schema.  The restrictions is on
how the rdf:type property is used in the syntax as an XML attribute.
This is mostly done in the grammar EBNF.  The syntax references I
pointed out in:

  http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2001Aug/0242.html

Note: This is about the use of rdf:type as an attribute in *this* XML
syntax.  It does not restrict what rdf:type can point to in the model
or of course, anything in other syntaxes.

Although, for all uses I can remember in RDF/XML rdf:type is used
with a URI-reference, the following is perfectly legal RDF/XML:

  <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
    <rdf:Description rdf:about="http://example.org/">
      <rdf:type>literal</rdf:type>
    </rdf:Description>
  </rdf:RDF>

and generates
  <http://example.org/> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> "literal" .


<snip/>
> I'm not a big fan of this exception. While we're cleaning up
> this mess, I suggest we get rid of it.

No.  This part of the syntax has a legitimate use and is not too
difficult to work out what the grammar meant.  We should not just
throw out syntax with no good reason.


> > Consequences:
> >   rdf:subject and rdf:predicate if used in XML attribute form will
> >   generate literal values which are presently forbidden (I think!)
> 
> I think not. They might not make much sense, but they're not forbidden.
> 
> >   or maybe just very unexpected.
> 
> quite possibly.


After emailing that, I changed my mind on illegal - unspecified would
be better.

<snip/>

Dave
Received on Thursday, 30 August 2001 18:49:22 EDT

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