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RE: Update on RDF in XHTML (generalizing to XML)

From: Dan Connolly <connolly@w3.org>
Date: Tue, 13 Jan 2004 15:31:25 -0600
To: "Butler, Mark" <Mark_Butler@hplb.hpl.hp.com>
Cc: 'Joseph Reagle' <reagle@w3.org>, Dominique HazaŽl-Massieux <dom@w3.org>, public-rdf-in-xhtml-tf@w3.org
Message-Id: <1074029485.23705.3188.camel@dirk.dm93.org>

On Mon, 2003-11-24 at 11:55, Butler, Mark wrote:
> Hi Dan, Joseph
> 
> On SIMILE (http://web.mit.edu/simile/www) we have been doing quite a bit of
> work on using XSLT to create RDF from XML. Some of the conclusions I have
> reached may be relevant here:

yes, quite.

At the XML 2003 "Practical RDF" town hall meeting...
  http://rdfig.xmlhack.com/2003/12/12/2003-12-12.html#1071189051.231090
James Clark gave similar feedback; i.e. why not generalize and
do this for all of XML, not just XHTML? TimBL gave similar input.

And so...

On Tue, 2004-01-13 at 08:01, Dominique HazaŽl-Massieux wrote:
> In addition to the changes evoked above, I've also started to add the
> generalization to XML, plus the definition of the RDF property Tim
> requested to link an XML Namespace to an interpreter; let me know if you
> think I've captured it adequately.

I'd like your take on this, Mark. Or... 

Mark wrote:
> 
> 1. Letting people create RDF from XML using XSLT, rather than encouraging
> everyone to use RDF/XML regardless is probably a good thing, and may lead to
> better RDF data models. 
> 
> When people create XML, they are concerned about their own needs, rather
> than how to model their data so it is globally unambiguous. Therefore I
> observe that allowing people to create data as XML, and then using XSLT to
> style it to RDF when required, means that they only have to concentrate on
> the latter requirements when they need to, so stand a better chance of
> getting it right. 
> 
> In SIMILE, we are still refining our RDF model for our data, but as we are
> using XML as a canonical format, currently its just a matter of using an
> XSLT transform to change the model, rather than hand editing a lot of data,
> and this is rather attractive.

Can you point me/us at a few of these? I'd like to see if the design Dom
and I are working on works with them.


>  So creating RDF from XHTML via XSLT might
> have similar benefits. 
> 
> 2. XSLT 2.0 is much better at this task than XSLT 1.0,

Hmm... good to know.


>  and ideally XSLT
> needs a function for URI encoding

Yes; that was on the list for XSLT 1.1; I was disappointed when
they decided to skip to 2.0; hmm...


> XSLT 1.0 doesn't have many functions to manipulate the contents of elements
> or attributes, but when dealing with RDF it is highly desirable to be able
> to do this. One reason is you may want to assign unique URIs to data
> objects, so you may synthesise these URIs from the contents of elements or
> attributes. This means you have to ensure that the URIs are valid. In SIMILE
> this means we are using the XSLT 2.0 replace and regular expression
> functionality.  

Ah... interesting.

> EXSLT includes proposals for functions for encoding and decoding URIs
> http://www.exslt.org/str/functions/encode-uri/
> and they were implemented by FourThought in 4Suite, and I note the
> FourThought folks have been quite active in using RDF. So my guess is that
> such functions would be potentially useful here. 

Yes.

> 3. Having to transform using XSLT to RDF/XML, and then deserialize is a pain
> - in an ideal world the reader would process the transform on the fly.
> 
> I realise this is a bit like trying to run before you walk, but particularly
> when dealing with very large models it is desirable to stream them directly
> into the RDF model rather than transform them, save them to disk, and then
> deserialize them.

Hmm... yes...

>  Some groups work with Python or Perl to convert XML to
> RDF/XML, so similar approaches could be used with XHTML with the advantage
> that you could convert it directly to the RDF model. However it would be
> good if it was possible to do this with XSLT also, so perhaps there is a
> need for a variant of XSLT that could support this - an area for future
> work. 
> 
> I plan to write up the SIMILE work in more detail in the future, but I'm
> afraid it will be the new year before this happens. 

If/when you do, please let me/us know.

> hope this is of interest, kind regards
> 
> Dr Mark H. Butler
> Research Scientist                HP Labs Bristol
> mark-h_butler@hp.com
> Internet: http://www-uk.hpl.hp.com/people/marbut/
-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Tuesday, 13 January 2004 16:31:26 GMT

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