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RE: RDFa reliance on namespace declaration

From: Misha Wolf <Misha.Wolf@reuters.com>
Date: Wed, 14 Jun 2006 13:48:22 +0100
To: Ian Davis <iand@internetalchemy.org>, public-rdf-in-xhtml-tf@w3.org
Cc: www-tag@w3.org, newsml-2@yahoogroups.com
Message-id: <A29ADE959C70A1449470AA9A212F5D80020C997B@LONSMSXM06.emea.ime.reuters.com>

Hi Ian,

Good point.  NewsML 2 has also taken your approach #2.  What syntax 
is eRDF using for this?

Misha
------------------- NewsML 2 resources ------------------------------
http://www.iptc.org         | http://www.iptc.org/std-dev/NAR/1.0
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-----Original Message-----
From: public-rdf-in-xhtml-tf-request@w3.org
[mailto:public-rdf-in-xhtml-tf-request@w3.org] On Behalf Of Ian Davis
Sent: 14 June 2006 09:41
To: public-rdf-in-xhtml-tf@w3.org
Subject: RDFa reliance on namespace declaration


I'd like to highlight a likely problem with RDFa's use of qname-like 
constructs in attribute values. I'm referring to CURIEs here but the 
same applies to any binding between XML namespace declarations and text 
content in the XML.

The problem lies with the coupling of the specific prefix used in the 
namespace declaration with the prefix used in content. Any XML 
processor, such as an XSLT stylesheet or a SAX pipeline, can change the 
namespaces prefix arbitrarily thereby breaking the syntactic link 
between the qname/CURIE used in the attribute and the namespace
declaration.

The breakage happens because the XML processor has no knowledge of the 
semantics of particular text content in specific attributes.

So, passing the following through a stylesheet:

<p class="contactinfo" about="http://example.org/staff/jo"
    xmlns:contact="http://www.w3.org/2001/vcard-rdf/3.0#">
     My name is
     <meta property="contact:fn">
         Jo Smith
     </meta>.
</p>

could very easily result in the following, with the consequent loss of 
all embedded triples:

<p class="contactinfo" about="http://example.org/staff/jo"
    xmlns:xyz="http://www.w3.org/2001/vcard-rdf/3.0#">
     My name is
     <meta property="contact:fn">
         Jo Smith
     </meta>.
</p>


As far as I can tell the only solutions are:

1) replace use of CURIEs in content with namespaced elements/attributes

2) replace namespace declaration mechanism with declarations based in 
the actual content with semantics specified by RDFa

3) replace CURIEs in content with full URIs

4) change XML namespaces spec to somehow understand CURIEs/qnames in
content

I think 1 is unlikely given that we're working within the limits of DTD 
and XSD validation

2 is the approach used by eRDF

3 would work for copy and paste at the expense of looking ugly, but I 
don't believe visual impact is a requirement of RDFa?

4 seems difficult and would introduce yet another dependency for RDFa 
adoption

Ian
-- 
http://purl.org/NET/iand
Blogging at... http://iandavis.com/blog
Working on... http://directory.talis.com/



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Received on Wednesday, 14 June 2006 12:48:44 GMT

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