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POWDER-related questions about RDFa linkage

From: Phil Archer <parcher@icra.org>
Date: Thu, 01 Nov 2007 11:36:27 +0000
Message-ID: <4729BA3B.4070102@icra.org>
To: "Hausenblas, Michael" <michael.hausenblas@joanneum.at>
CC: public-powderwg@w3.org, RDFa <public-rdf-in-xhtml-tf@w3.org>

Michael,

As you and others have been kind enough to look at the potential usage 
of RDFa and POWDER, I'd like to ask a couple of questions please.

I'd like to significantly improve what we say about RDFa, either in the 
Rec Track Description Resources doc [1] or, if more appropriate, in a 
non-normative POWDER Primer we'll be starting work on later this month.

Easier question first. Can I ask you for a sanity check on this example 
please:

Example 1
=========

<html
   xmlns="http://www.w3.org/1999/xhtml"
   xmlns:wdr="http://www.w3.org/2007/05/powder#"
 >
   <head>
     <title>The English Civil War</title>
     <link rel="wdr:describedBy" 
href="http://education.example.org/powder.rdf#DR_1" />
   </head>
   <body>
     
     <p>Charles I came to the throne believing in his Divine Right to 
rule...
     
   </body>
</html>

That is, a single use of wdr:describedBy at document level. Actually, 
for this kind of linkage from an HTML doc, the usual way will be to use 
an HTML profile we're drafting and a relationship type of powder thus:

Example 2
=========

<html xmlns="http://www.w3.org/1999/xhtml">
    <head profile="http://www.w3.org/2007/10/powder-profile">
       <link rel="powder"
          href="http://education.example.org/powder.rdf#DR_1" />
       <title>The English Civil War</title>
    </head>
    <body>
       <p>Charles I came to the throne believing in his Divine Right to 
rule...</p>
    </body>
</html>

But I'm really hoping that RDFa can be used for more powerful things. In 
particular, that we can use it to link to a Description Resource that 
describes the target of a hyperlink as simply as possible. If I 
understand RDFa correctly that means doing something like this:

Example 3
=========

<html
   xmlns="http://www.w3.org/1999/xhtml"
   xmlns:wdr="http://www.w3.org/2007/05/powder#"
 >
   <head>
     <title>The English Civil War</title>
     <link rel="wdr:describedBy" 
href="http://education.example.org/powder.rdf#DR_1" />
   </head>
   <body>
     
     <p>Charles I came to the throne believing in his
     <link about="#divRight" rel="wdr:describedBy"
          href="http://education.example.org/powder.rdf#DR_2">
     <a href="http://education.example.org/divine_right.html"
          id="divRight">Divine Right</a> to rule...
     
   </body>
</html>

So we have a hyperlink in the document to one about divine right. That 
second document is the subject of a triple thus:

<http://education.example.org/divine_right.html>
   wdr:describedBy
<http://education.example.org/powder.rdf#DR_2>

is there a more terse way of creating this triple within the RDFa/XHTML?

I guess the problem is that would entail having two href attributes in a 
single hyperlink, which is silly, but the use cases are pretty clear for 
us. For example, imagine that the English Civil War document is mobileOK 
and is being displayed on a mobile device - should my browser display 
the hyperlink to the divine right document or not? If it's mobileOK too 
(as declared in DR_2) then the answer's yes, if not, then just show the 
text without the hyperlink.

Finally, how far can we go in a Rec Track document that we're hoping to 
declare as at Last Call after next week's face to face? Is Example 1 
sound? Is Example 3 sound?

Thanks very much for your help,

Phil.

[1] http://www.w3.org/TR/2007/WD-powder-dr-20070925/#semlink
Received on Thursday, 1 November 2007 11:36:41 GMT

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