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RE: RDFa Lite and non-RDFa @rel values

From: Grant Robertson <grantsr@gmail.com>
Date: Wed, 25 Apr 2012 00:11:42 -0700
To: "'Alex Milowski'" <alex@milowski.com>, "'RDFa WG'" <public-rdfa-wg@w3.org>
Message-ID: <BBECF4F0B4B7425C96B82B430F3F07FB@grantdesk>
Again, I don't know if I get a "vote" but:

I agree that this is a serious problem. I believe that the instant someone
decided to repurpose the rel attribute from HTML for use within RDFa, they
doomed RDFa to this problem. Any time you re-use a field or variable for
some special purpose, while it is still being used for its original purpose,
you are bound to come across these issues. But there is no way anyone would
accept deprecating @rel for use within RDFa and switching to some other
character string to use for that same purpose. Sure, it would be an easy
edit in all the processors to switch to the new attribute. But backwards
compatibility in documents would be a nightmare. So, you are stuck with
things as they are.

However, I can always just explain to web developers - in the user
documentation I will be writing - how to avoid the problem when they author
web pages. 

In that vein: Alex, I think I may have found the hack you need to solve the
dilemma you presented in a previous message. You said:

> ... the real question comes down to what we expect 
> from this kind of markup:
> 
>    <a vocab="..." href="http://www.w3.org/" rel="nofollow"
> property="homepage">W3C's Home Page</a>
> 
> Should it be:
> 
>    <> <http://www.w3.org/1999/xhtml/vocab#nofollow> 
> <http://www.w3.org/>
>    <> <...homepage> "W3C's Home Page"
> 
> or
> 
>    <> <http://www.w3.org/1999/xhtml/vocab#nofollow> 
> <http://www.w3.org/>
>    <> <...homepage> <http://www.w3.org/>
> 
> ?
> 
> Note that you can't get the second set of triples from the 
> same link (@href value) through some other structure without 
> repeating the link element somehow.


I think you can achieve the second set of triples - without repeating the
link value - using the following HTML markup:

<!-- 
   Comments just before an element indicate what was passed down
   from a parent element.
   
   Comments just after an element indicate what occurs within the
   element.
 -->
 
<span vocab="" prefix="foaf: http://xmlns.com/foaf/0.1/">
<!-- Resets default vocabulary to host language default. -->
<!-- Sets the foaf prefix -->

   
   <!-- [parent object] = [base] -->

   <a href="http://www.w3.org/" rel="nofollow">

   <!-- [new subject] = [parent object] = [base] -->
   <!-- [current object resource] = "http://www.w3.org/"  -->
   <!-- Triples Generated:
      <> <http://www.w3.org/1999/xhtml/vocab#nofollow>
         <http://www.w3.org/> .
         // While this seems like a useless, bogus triple it actually
         // does convey some information, if you mentally redefine
         // "nofollow" slightly for use within RDF.
   -->

   
      <!-- [parent object] = [current object resource] = 
           "http://www.w3.org/"  -->

      <span rev="foaf:homepage" resource="">W3C's Home Page</span>

      <!-- [new subject] = [parent object]
            = "http://www.w3.org/"  -->
      <!-- [current object resource] = "" = [base]
           // See Section 7.4 -->      
      <!-- Triples Generated:
         <> <foaf:homepage>  <http://www.w3.org/> .
      -->

   </a>
</span>   



I apologize if the actual markup gets a little lost amonst all the comments,
but I had to write out all the comments to make sure I had my logic
straight. And so you could too.   ;^)

Grant



> -----Original Message-----
> From: Alex Milowski [mailto:alex@milowski.com] 
> Sent: Tuesday, April 24, 2012 3:15 PM
> To: RDFa WG
> Subject: Re: RDFa Lite and non-RDFa @rel values
> 
> On Tue, Apr 24, 2012 at 2:48 PM, Dan Brickley 
> <danbri@danbri.org> wrote:
> >
> > I appreciate there's potentially an issue here, but hope 
> there's some 
> > mechanism for dealing with it quickly so would-be adopters can move 
> > ahead with adopting...
> >
> 
> One mechanism is to just leave everything alone.  I might 
> have preferred a different outcome but I can live with the status quo.
> 
> I think we could go around and around on this one and messing 
> with @rel values feels dangerous.
> 
> --
> --Alex Milowski
> "The excellence of grammar as a guide is proportional to the 
> paucity of the inflexions, i.e. to the degree of analysis 
> effected by the language considered."
> 
> Bertrand Russell in a footnote of Principles of Mathematics
> 
Received on Wednesday, 25 April 2012 07:12:02 GMT

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