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Re: RDF/XML (was Re: My action item on RDDL/RDF)

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Date: Tue, 12 Nov 2002 21:30:18 +0000
To: Paul Prescod <paul@prescod.net>
cc: WWW-Tag <www-tag@w3.org>
Message-ID: <27487.1037136618@hoth.ilrt.bris.ac.uk>

>>>Paul Prescod said:
> Perhaps I'm naive but I don't think this thread will go on long so I 
> prefer to finish it up here.

We'll see ;)  I'll try choping bits out...


> ... If you know that there are huge problems and the only 
> thing preventing you from fixing them is process then I have no idea why 
> you take offense to the assertion that the current syntax is broken.

I'm not taking offence, just trying to work out if you have any new
information.  This mixed content problem, I still can't work out what
you, or others are seeing is the concern.


> Simple:
> <Class>
>     <Property>
>        <rdf:literal>
>           <p>This <emph>is</emph> easy.</p>
>        </rdf:literal>
>      </Property>
> </Class>

so rdf:literal is a class or some special syntax?

You'll need to explain this in RDF triples since *that* is the model,
not this RDF/XML.

So is the above one of these triples?

   Subject node  Predicate arc        Object Node
1  URI of Class  URI-ref of Property  the XML "<p>....</p>"
2  URI of Class  URI-ref of Property  the XML "<rdf:literal>...</rdf:literal>"
3  URI of Class  URI-ref of Property  something else??


1 can already be done in RDF/XML by:
     <Property rdf:parseType="Literal>
        <p>This <emph>is</emph> easy.</p>


> At least the transfer syntax. There should probably be thought given to 
> whether it is desirable to have some form of use-by-reference of the 
> infoset in the RDF model and vice versa. But fixing the RDF/XML syntax 
> is a good start.

RDF Core thought about the infoset as RDF; I think there is still
some work on that intended, and a note already there.  I'd have to
look up the pointers.

> I see a syntax for RDF to refer to mixed content and literal XML. I see 
> nothing for having RDF embed mixed content and literal XML.

I'm not sure what you are getting at here.

> > 3: I don't understand "other type-declared data" - please cite
> >    something more specific.
> <Class>
>     <Property>
>        <rdf:literal rdf:type="xsi:integer">5</rdf:literal>
>      </Property>
> </Class>
> <Class>
>     <Property>
>        <rdf:literal rdf:type="xsi:real">5</rdf:literal>
>      </Property>
> </Class>

Maybe you'll be happy to know we have added typed literals to RDF and
RDF/XML, so that the following is legal:

     <Property rdf:datatype="&xsd;integer">5</Properyt>

(the attribute value is a URI-reference, I'm abbreviating here).

  Typed Literals

Maybe the examples in the new syntax draft, out today, might help

> ... Anybody with SGML experience should have been able to see that 
> mixed-content literal values would be important.

They are there, as far as I understand it.  I'm now really unsure if I do.


> XHTML addresses RDF in XHTML. The RDF core team has to address XHTML 
> (and other vocabularies that use mixed content) in RDF.

Oops, I got it backwards.

We've a place that you can put any XML element content you like
(rdf:parseType="Literal") and it'll stay preserved as such.  That
seems sufficent.  Are you asking to do it without actually matching
RDF/XML's grammar.  That's more tricky, since you can't tell when the
user meant it as RDF/XML, or as some other XML language element.  You
have to give the parser some kind of hint.  The rdf:literal thing is
a hint, but RDF/XML already has an equivalent hint in
rdf:parseType="Literal" on a property element.

> > I'd hope this is in the vein of gathering requirements for new
> > syntaxes, rather than chopping and changing this one.
> I would say that some of the problems of the current syntax could be 
> fixed. A richer vocabulary of literals could be a new feature. Having an 
> entirely new syntax is probably also important as another project.

I'm increasingly thinking you need to check out RDF Core's updates.
We've just added typed literals and are in the process of explaining
it with new working drafts, the ones I've linked above are just out.
There is a new RDF Concepts and Abstract Syntax WD also out,
new Primer WD should follow soon.


Thanks for the feedback

Received on Tuesday, 12 November 2002 16:33:08 UTC

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