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Re: Rethinking @src in the context of chaining rules

From: Mark Birbeck <mark.birbeck@formsPlayer.com>
Date: Mon, 7 Jan 2008 13:10:43 +0000
Message-ID: <a707f8300801070510m105b388fnb59e6816805d6542@mail.gmail.com>
To: "Ben Adida" <ben@adida.net>
Cc: RDFa <public-rdf-in-xhtml-tf@w3.org>

Hi Ben,

Shane has pointed out to me that I completely missed the core of this proposal.

When we discussed using @src as a subject on the telecon [1], I was
quite happy with it because it actually 'already worked' on the
chaining rules I had proposed. But of course I wasn't listening
carefully enough. :( I didn't realise that the suggestion was to
remove the ability for @src to express an object, and replace it with
being a subject.

> As per my action item from last week, here are some thoughts on @src
> given the new chaining rules.
> PROPOSAL: @src defines a subject, not an object. @about overrides @src
> in the same way that @resource overrides @href.

My idea was that @src defines a subject when there is no @rel, but can
still define an object. Note the example I pasted into the meeting

  <markbirbeck_> Would be interesting to know if Ivan would be happy with:
  <markbirbeck_> <div about="#a" rel="a:b">
  <markbirbeck_> <img src="http://a.b.c" instanceof="w:p"/>
  <markbirbeck_> </div>

Which is what we've ended up with. But what I was trying to stress was
the lack of a @rel with @src; I wasn't trying to suggest that we drop
the whole formulation of @src being a subject.

> Arguments:
> 0) Given that an image is inline, it would be quite odd not to be able
> to declare an @instanceof on that image using simply:
> <img src="foo.jpg" instanceof="foaf:Image" />

Agreed. As with @about, this sets a subject. But due to chaining
rules, it may not be *only* a subject, and it may also set an object:

  <div about="#ben" rel="foaf:depiction">
    <img src="foo.jpg" instanceof="foaf:Image" />

The point I'm keen to keep stressing is that once you adopt the notion
of chaining, then attributes are able to be subjects, objects or both,
depending on context.

> 1) Having three different ways to specify an object, @resource, @href,
> and @src is probably a sign of bad design.

I don't agree. :) That would imply that anything more than the
attributes @subject, @predicate and @object is bad design. ;)

> 2) Declaring a foaf:img is trivial with the new chaining rules, even
> when @src is the subject:
> <div about="#me" rel="foaf:img">
>  <img src="foo.jpg" instanceof="foaf:Image" />
> </div>

Right, that's agreed. But what about this:

  <img about="#me" rel="foaf:img" src="foo.jpg" />

I don't see why we don't retain support for that. The presence of @rel
is what turns some of the attributes into objects.

> 3) Using @about to override @src allows for just the kinds of situations
> where the rendered does not quite match the semantic: e.g. you used a
> thumbnail picture but you want to declare a semantic relationship with
> the full-size image.


> 4) Ivan is happy :)
> Okay, I could come up with more, but I'll just say that, given the clean
> design of Mark's chaining rules, the @src-as-subject proposal just makes
> sense in my mind.

And I apologise for not spotting this before...but I thought we were
going for the "@src-as-subject-or-object proposal".



[1] <http://www.w3.org/2007/12/13-rdfa-minutes.html#action12>

  Mark Birbeck, formsPlayer

  mark.birbeck@formsPlayer.com | +44 (0) 20 7689 9232
  http://www.formsPlayer.com | http://internet-apps.blogspot.com

  standards. innovation.
Received on Monday, 7 January 2008 13:10:49 UTC

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