W3C home > Mailing lists > Public > www-rdf-interest@w3.org > April 2001

RE: RDF in XHTML

From: Jonathan Borden <jborden@mediaone.net>
Date: Wed, 18 Apr 2001 22:18:30 -0400
To: "Murray Altheim" <altheim@eng.sun.com>
Cc: "RDF Interest" <www-rdf-interest@w3.org>
Message-ID: <003801c0c877$06b85120$0201a8c0@ne.mediaone.net>
Murray Altheim wrote:

> >
> > For example, to address the int datatype, the URI is:
> >
> >       http://www.w3.org/2000/10/XMLSchema#int
>
> Each of these could be described by a notation. I'm in fact doing this
> exact thing in a spec I'm working on to add datatypes to XTM.

Sure, notations could be used except that the big win in terms of URIs _is
that dereferencing the URI takes us to the type definition_. URIs are a core
feature of RDF and are what makes RDF interesting for Web applications.

Perhaps in another world where an FPI resolution infrastructure existed ...

>
> > > The XML Schema approach is also markedly different, which is to
> > > *validate*
> > > the content.
> >
> > ok, but suppose <!ELEMENT rdf:RDF ANY> modulo namespace prefix
> difficulties
> > of DTDs. The XHTML document can validate and the RDF content can be
> > constrained perhaps by an RDF Schema.
>
> No, this is a common misunderstanding. "ANY" doesn't mean any content, it
> means any configuration of already-declared elements, and not even mixed
> content.

duh! i shouldn't have used this example. the point I am trying to press is
that using schemata identified via a namespace, a compound namespace
document (such as most RDF documents are) can be schema validated.

> >
> > Being an independent (and keeping this discussion entirely away from W3C
> > issues) the thing that most definitively converted me from the
> DTD approach
> > and toward the XML schema (small 's') approach is the
> comparison of XHTML as
> > described by a DTD vs. TREX and RELAX (the RDDL spec contains
> all 3 schemata
> > for RDDL).
>
> Hmm. I find that curious. If I were to remove all the
> Murray-isms, that is,
> all the "unnecessary" comments and conditional sections, you'd likely find
> that XHTML modularization is about an order of magnitude less complex than
> the XML Schema approach, and still more concise than any of the markup-
> based approaches. My take on this is that the only way a non-DTD schema
> designer is going to want to write complex schemas is with a
> tool, as there's
> a lot more angle bracket stuff to type than in a DTD, which
> despite its non-XML
> syntax isn't *really* all that complex.

If you are curious perhaps look at the various schemata referenced in
http://www.rddl.org/

Having made my way through the XHTML Modularization DTDs as well as, for
example, James Clark's TREX Schema for XHTML, I'd say that the TREX Schema
is strikingly less complex (and much more concise). If you claim that the
DTDs are more complex than need be, I'd say the proof is in the pudding,
that is to say the current evidence does not support this claim. Clearly
there is work required to make namespaces play nice with modularized DTDs
that _significantly_ adds to the DTD complexity. For example IE5 chokes
trying to validate modularized XHTML as does XML Authority (the only
validator up to the task in my experience is STG's). My impression is that
these modularized DTDs are in fact quite complex. No?

What I am suggesting is that by referencing a schema by the namespace URI
(e.g. within a RDDL document), multiple namespace applications such as RDF +
XHTML can schema validate and in a straightforward fashion.

Jonathan Borden
The Open Healthcare Group
http://www.openhealth.org
Received on Wednesday, 18 April 2001 22:18:17 GMT

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