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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,
Consult with Dan and Ralph about the gap between the XHTML namespace and
the GRDDL transformation for RDFa

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.

> 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 15:21:51 UTC

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