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Re: [HTML+RDFa 1.1] section 3.1 and 2.1

From: Ivan Herman <ivan@w3.org>
Date: Thu, 31 Jan 2013 13:05:01 +0100
Cc: public-rdfa-wg@w3.org
Message-Id: <FBBFB948-AAFB-4E08-8480-81E3305F1619@w3.org>
To: "Dr. Olaf Hoffmann" <Dr.O.Hoffmann@gmx.de>

To be honest, I am not sure how to solve these issues, and I would welcome your suggestions. We face two problems here.

In (X)HTML5 the @version attribute does not exist any more. In previous versions of RDFa we made use of that attribute and, actually, RDFa 1.1 Core still refers to this attribute for, eg., XHTML1.0. Processors hitting the @version value referring to RDFa 1.0, for example, are supposed to process accordingly. But, as I said, this option is not available any more in (X)HTML5...

Of course, we could define a separate attribute, much like we do have a number of RDFa 1.1 attributes. But there comes the next issue: many authors, or indeed 'webmaster advices' issued by companies like Facebook, ignore that attribute anyway. The practice is that authors do not use it. Ie, we did not want to rely on the presence of such attribute to control an RDFa processor. Meaning that we have to define a behaviour in the absence of any additional hints.


On Jan 31, 2013, at 11:54 , "Dr. Olaf Hoffmann" <Dr.O.Hoffmann@gmx.de> wrote:

> Hello, 
> the working draft
> http://www.w3.org/TR/2012/WD-rdfa-in-html-20121213/
> as well as this variant from today 
> http://www.w3.org/2010/02/rdfa/sources/rdfa-in-html/
> contain in section 3.1 the sentence:
> "Documents served as application/xhtml+xml, that don't contain a DTD, and 
> don't specify a @version attribute must be interpreted as XHTML5+RDFa 1.1 
> documents."
> Does this mean, that if for example in 20 years I write an XHTML6+RDFa 2.0
> document, there will be a DTD or version indication again to ensure, that
> the document will be interpreted as XHTML6+RDFa 2.0 and not as
> XHTML5+RDFa 1.1?

Hopefully RDFa 2.0 would be backward compatible with RDFa 1.1, ie, it would not matter (although I know this is not 100% sure with RDFa 1.0/1.1 :-(. And if this is not the case, then indeed some new attributes may have to be used. Actually, this issue will come up regardless of RDFa: What will happen with XHTML5 vs. XHTML6? Maybe some mechanism will be introduced by the HTML WG of the time to ensure that.... 

> How to indicate precisely, that a document is of version XHTML5+RDFa 1.1,
> because section 2.1 only notes:
> "XML mode XHTML5+RDFa 1.1 documents should be labeled with the Internet Media 
> Type application/xhtml+xml as defined in section 12.3 of the HTML5 
> specification [HTML5], must not use a DOCTYPE declaration for XHTML+RDFa 1.0 
> or XHTML+RDFa 1.1, and should not use the @version attribute."
> This does not implicate, how to indicate an XHTML5+RDFa 1.1 at all.
> Doesn't this finally mean, that one effectively cannot write an 
> XHTML5+RDFa 1.1 document at all, because one cannot indicate, that
> the document follows this version?

I am not sure I follow your argument. XHTML5+RDFa 1.1 is the 'default' for application/xhtml+xml, unless a DTD says otherwise (ie, points at XHTML1 and/or RDFa 1.0). Of course, if it uses a DTD, it is not XHTML5 any more, but it can still be XHTML1.1.

Again, this is primarily an (X)HTML issue, ie, an issue of XHTML5 vs. XHTML1.1. RDFa just follows the XHTML5 rules here...


> Or should one indicate the relation for example with a DCMI Term
> (http://dublincore.org/documents/2012/06/14/dcmi-terms/)
> like conformsTo or  format with the URI of the specification as value?
> Is this the currently preferred approach for all types of (X)HTML5-documents,
> because they currently have no version indication itself?
> Or is there a simpler method without the need of other formats to
> indicate, that one has an (X)HTML5 document and not something else?
> Olaf

Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
mobile: +31-641044153
FOAF: http://www.ivan-herman.net/foaf.rdf

Received on Thursday, 31 January 2013 12:05:29 UTC

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