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Re: Treatment of RDFa in TAG Finding on Self-describing Web

From: Mark Baker <distobj@acm.org>
Date: Thu, 11 Sep 2008 01:01:05 -0400
Message-ID: <e9dffd640809102201m3a9c9fado545cbec992842fde@mail.gmail.com>
To: noah_mendelsohn@us.ibm.com
Cc: "Steven Pemberton" <steven.pemberton@cwi.nl>, "Ben Adida" <ben@mit.edu>, www-tag@w3.org

Noah,

On Tue, Sep 9, 2008 at 5:52 PM,  <noah_mendelsohn@us.ibm.com> wrote:
> * You then quote the RDFa Syntax and Processing draft: "There SHOULD be a
> @version attribute on the html element with the value 'XHTML+RDFa 1.0;".
> Let's for the moment ignore that it's a SHOULD and consider the case where
> @version is indeed set this way.  Is there something in RFC 3236 or XHTML
> 1.0 to the effect that "a value in the @version attribute of the HTML
> element is a key that can be used to identify additional specification(s)
> that provide normative interpretations for markup beyond that which is
> standardized for XHTML itself?"  As best I can tell, XHTML delegates
> discussion of the <HTML> element to HTML 4.01, and that in turn says that
> the version attribute is deprecated! [1]  Is there something normative in
> either XHTML or M12N that says "go looking for a specification that seems
> to have been written by the authority responsible for the namespace used
> in the new markup?".
>
> So, I'm still missing some crucial connections.=

I think there is one connection missing; RDFa extends the meaning of
rel (and rev) attribute values in a manner which HTML doesn't licence.

Often, IME, doing that sort of thing is a really bad idea, but not
always.  In this case, rel attribute values are a fairly simple
element of HTML, as they're just a list of opaque strings from a small
dictionary, and AFAIK, there's no processors which try to treat them
as anything more than that.  So RDFa's introduction of special meaning
to a colon - a character unused in that dictionary - is effectively
harmless.

That's not the end of the story of course, because while RDFa isn't
self-descriptive, it should be made so.  What that requires is an
update to HTML to anoint the special meaning of ":" in link types;

 http://www.w3.org/html/wg/html5/#linkTypes

So for your draft, you might consider expanding 4.1 to explain in more
detail what it means to extend an existing media type
self-descriptively in both the short and long term.

Mark.
Received on Thursday, 11 September 2008 05:01:41 GMT

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