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Re: Treatment of RDFa in TAG Finding on Self-describing Web and feed back on RDFa in XHTML1.1

From: Dean Edridge <dean@dean.org.nz>
Date: Fri, 03 Oct 2008 20:22:20 +1300
To: Steven Pemberton <steven.pemberton@cwi.nl>
Cc: noah_mendelsohn@us.ibm.com, www-tag@w3.org, Mark Baker <distobj@acm.org>, Ben Adida <ben@mit.edu>, RDFa <public-rdf-in-xhtml-tf@w3.org>
Message-id: <48E5C82C.2090706@dean.org.nz>


I have some feedback on the RDFa in XHTML1.1 specification.

I request that having a doctype for RDFa in XHTML1.1 documents become a 
MUST (compulsory), and not optional. As most people send their XHTML 
documents as text/html [1], a doctype will be needed to trigger 
standards mode, plus the lack of a doctype creates a conflict with the 
XHTML variant of HTML5.

Steven Pemberton wrote:
> On Tue, 09 Sep 2008 02:53:56 +0200, <noah_mendelsohn@us.ibm.com> wrote:
>> As I have mentioned previously on this list, I am trying to wrap up the
>> TAG finding on the Self-Describing Web [1], and the major unresolved
>> question is whether there is a chain of normative specifications,
>> presumably starting with the media type registration for
>> application/xhtml+xml [2], that justifies the inference of RDF 
>> triples in
>> an XHTML document that uses RDFa.
> Hi Noah.
> The RFC for application/xhtml+xml says
>       With respect to XHTML Modularization [XHTMLMOD] and the existence
>       of XHTML based languages (referred to as XHTML family members)
>       that are not XHTML 1.0 conformant languages, it is possible that
>       'application/xhtml+xml' may be used to describe some of these
>       documents.
> http://www.ietf.org/rfc/rfc3236.txt
> "RDFa in XHTML: Syntax and Processing" (which uses XHTML 
> Modularization) says:
>     XHTML+RDFa documents SHOULD be labeled with the Internet Media 
> Type "application/xhtml+xml" as defined in [RFC3236].

The thing to keep in mind here is that based on the relatively small 
adoption rate of the XHTML mime type up until now [1], it would seem 
that the vast majority of RDFa in XHTML1.1 documents aren't going to be 
served over HTTP using the XHTML mime type, so perhaps the mime type can 
not be relied upon to identify a RDFa in XHTML1.1 web page (if that's 
what people were actually hoping to do). I don't think anyone can say 
the document is identified by the mime type, and then say the XHTML mime 
type (application/xhtml+xml) is optional for XHTML web pages [2] [3]

> http://www.w3.org/TR/rdfa-syntax/#docconf
> (Note that XHTML+RDFa is the first version of XHTML that doesn't 
> require a DTD declaration to identify itself.

I'm sorry, but that's not correct. The XHTML variant of the HTML5 
specification, which has been around for four years now, can only be 
sent with a XML mime type such as application/xhtml+xml or 
application/xml), so therefore does not need to have a doctype (as the 
mime type triggers standards mode) or a DTD (although there is an 
optional one). It is identified by the root namespace and the mime type 
(application/xhtml+xml or application/xml) [4] And it is the mime type, 
namespace and lack of a doctype that allow user-agents and validators to 
identify a web page as being the XHTML variant of HTML5. Having two 
documents that look the same but are developed by different working 
groups may cause problems for people such as Olivier Thereaux that are 
going to need to configure the W3C_Validator to identify and validate 
these web pages. So I think a doctype for RDFa in XHTML1.1 should be a MUST.

Here's some links to clarify:


> That notwithstanding, there is also a DTD available, since current 
> browsers use the existence of a DTD declaration to switch itself into 
> Standards Mode).

I think you mean the doctype switch triggers standards mode. Since most 
people are going to serve their pages as text/html, they'll be needing a 
doctype to trigger standards mode in browsers. [5] If authors don't wish 
to reference a DTD, authors could just use a doctype like the one below 
without the usual DTD reference.

    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML+RDFa 1.1//EN" "">

[1] http://goer.org/Markup/TheXPhiles/
[3] http://www.w3.org/MarkUp/2008/ED-xhtmlmime-20080827/#text-html
[4] http://www.w3.org/html/wg/html5/#authors-using-xhtml
[5] http://hsivonen.iki.fi/doctype/

Best Regards

Dean Edridge
Received on Friday, 3 October 2008 07:22:56 UTC

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