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Re: My action item on RDDL/RDF

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Date: Mon, 11 Nov 2002 10:29:07 +0000
To: Paul Prescod <paul@prescod.net>
cc: Tim Bray <tbray@textuality.com>, WWW-Tag <www-tag@w3.org>
Message-ID: <20492.1037010547@hoth.ilrt.bris.ac.uk>

>>>Paul Prescod said:
<snip/>
> Tim Bray said:
> > and you get no contradictions.  BUT, you get way more tangled-looking 
> > syntax and it gets way harder to predefine a bunch of precooked purpose 
> > vocabularies AND it gets harder to automatically detect the "purpose" 
> > property.  So this would be an example of the "RDF tax" that has for 
> > example doomed the RDF version of RSS.
> 
> First, could you please be more concrete about all of these? A syntax 
> example would be helpful. I could guess but an RDF-in-XML expert may 
> know short-cuts that I don't know. Also, is it harder to detect the 
> purpose for an RDF processor or just a general-purpose XML processor 
> with RDF knowledge?
> 
> Second, this is just further evidence that RDF/XML is broken. On a 
> project for a customer it would be appropriate to just hack around it. 
> But on a W3C project it seems that the right thing to do is track down 
> the people who can fix RDF/XML and get them to do so. If people who WANT 
> to use RDF properly feel that they cannot, that is a serious issue.

I normally just lurk here but I couldn't ignore this flame-bait.

I edit the RDF/XML specification (revising the existing syntax) so
here is how I see it.  One of RDF/XML's many original goals was to
enable it to be embedded in HTML (Tim Bray was on the original
working group and can correct me).  This is one of the reasons why it
has many (too many) abbreviated forms that allow you to express
statements without using element content; dumb HTML browsers will
ignore it.

As far as I've know, this was actually not used very much in
practice.  People prefered to use the <meta> tag with very simple
Dublin Core metadata, a <link> to an external file or some other
approach.

In the era of XHTML, validation and all that goodness, this
embedding-in-HTML approach requires lots of extra infrastructure to
keep validation - XHTML modularisation and new DTDs - so the RDF Core
working group recommended using the linking approach.  The latest
RDF/XML working draft, out today or tomorrow, records this in
  http://www.w3.org/TR/rdf-syntax-grammar/
(draft at
  http://ilrt.org/discovery/2001/07/rdf-syntax-grammar/#section-rdf-in-HTML
) 

Sean B. Palmer discussed this extensively in
  RDF in HTML: Approaches
  http://infomesh.net/2002/rdfinhtml/
which I recommend.


> Finally, a whole 'nother strategy is to define a mapping from an 
> optimized XML syntax into the RDF model.

Yes, and that is a good approach.

For the record:
   I do not expect all RDF graphs to be written in RDF/XML.

and indeed, I'm planning to add mapping code to my RDF parser by the
means of the XML mapping or transformation language, XSLT.  This will
allow scraping from any XML tag soup such as the RSS* ones ;)

> BTW, the 1.2 example is not well-formed:
> 
> <rdf:description about="http://example.org/schemas/L.rng
>      rddl:title="Relax NG Schema"
>      rddl:nature rdf:resource="http://relaxng.org/ns/structure/1.0"
>      rddl:purpose rdf:resource="http://www.rddl.org/purposes#validation"
>      rddl:prose rdf:resource="#rng-prose" />

This isn't RDF/XML or even XML?  There is a missing " on the first
line and then attributes without values.  I'm confused.

Dave
Received on Monday, 11 November 2002 05:29:56 GMT

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