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Re: Using RDFa to produce self-describing HTML

From: Dan Connolly <connolly@w3.org>
Date: Thu, 12 Jun 2008 10:21:26 -0500
To: Steven Pemberton <steven.pemberton@cwi.nl>
Cc: TAG <www-tag@w3.org>, XHTML WG <public-xhtml2@w3.org>, RDFa <public-rdf-in-xhtml-tf@w3.org>
Message-Id: <1213284086.21883.13.camel@pav.lan>

On Fri, 2008-06-06 at 12:38 +0200, Steven Pemberton wrote:
> Dear TAG members,
> 
> The RDFa Task Force and the XHTML 2 working group are aware that you had  
> some discussions about RDFa at your 20 May f2f meeting.  Thanks for  
> considering our document, and also our input during your meeting.  After  
> reviewing your minutes, we have had more discussions about it in the RDFa  
> task force (with XHTML 2 people present) and wanted to provide you with  
> some additional information.
> 
> First, we believe that what you are trying to do is tightly define how  
> engines on the semantic web can discover semantic relationships in a  
> deterministic way.  We agree that this is critical to the continued  
> evolution of the semantic web, and want to ensure that we participate  
> fully.  Thanks for bringing this important issue to our attention.
> 
> Second, we consider that XHTML documents have ALWAYS contained  
> relationship information, but without a well-defined mechanism for  
> extracting that information.  Therefore, it is reasonable to define the  
> way that this relationship information can be expressed as RDF.
> 
> However, we think this issue is independent of the media type used to  
> deliver the containing document. Sections of XHTML may be embedded in  
> other namespaces in multi-namespace documents, and delivered using a  
> non-XHTML related media type, and yet the RDF relationships should still  
> be extractable.
> 
> With these things in mind, we feel the best course of action is to declare  
> that all documents using the xhtml namespace http://www.w3.org/1999/xhtml  
> are capable of being interpreted to produce RDF triples.  In order to  
> support the follow-your-nose use case and support your semantic web model,  
> we propose that we update the document at the end of the namespace URI to  
> indicate there is a GRDDL processor (as described in [1]) AND that we  
> update the prose to indicate that RDF can be extracted using the rules  
> defined in the RDFa Syntax document [2].

Updating the namespace document is consistent with TAG discussions,
esp...
ACTION-130
Consult with Dan and Ralph about the gap between the XHTML namespace and
the GRDDL transformation for RDFa
http://www.w3.org/2001/tag/group/track/actions/130

As to "all documents using the xhtml namespace", the GRDDL mechanism[1]
only applies to the root namespace. If the XHTML stuff isn't at
the root, it seems to me that the root media type/namespace would
have to be somewhat explicit about delegating RDF extraction
down the tree.

The GRDDL WG tried to find a general mechanism but eventually
postponed the issue.
http://www.w3.org/2001/sw/grddl-wg/issues#issue-tx-element


> 
> We would like to know 1) is our assumption about your concerns correct,
> and 2) if this course of action would help address those concerns.
> 
> [1] http://www.w3.org/TR/2007/REC-grddl-20070911/#ns-bind
> [2] http://www.w3.org/MarkUp/Drafts#rdfa-syntax
> 
> Best wishes,
> Steven Pemberton
> For the XHTML2 WG and the RDFa TF
-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
gpg D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E
Received on Thursday, 12 June 2008 15:21:49 GMT

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