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Re: [RDFa] ISSUE-3 @class and @role for rdf:type

From: Mark Birbeck <mark.birbeck@x-port.net>
Date: Thu, 5 Jul 2007 14:42:30 +0100
Message-ID: <640dd5060707050642wbd1536eq2129c6c88800f3c8@mail.gmail.com>
To: "Steven Pemberton" <steven.pemberton@cwi.nl>
Cc: "Ivan Herman" <ivan@w3.org>, "Ben Adida" <ben@adida.net>, public-rdf-in-xhtml-tf@w3.org

Hi Steven

On 05/07/07, Steven Pemberton <steven.pemberton@cwi.nl> wrote:
> On Thu, 05 Jul 2007 13:26:30 +0200, Mark Birbeck <mark.birbeck@x-port.net>
> wrote:
>
> > My argument has always been that something 'playing the role of x', is
> > not the same as 'something being x', and so @role should not represent
> > rdf:type.
>
> I've never understood this argument, which seems to be based on what
> things mean in English. Something "being of class X" is also not the same
> as "something being X". But so what? The question is about the mapping to
> RDF.

The rationale for my argument has nothing to do with that slippery
language English, and everything to do with what things 'mean' in RDF.

In RDF, if you say something is of type 'x' then all sorts of other
statements become legitimate. So if I firstly say that 'a toolbar' has
a property of 'collection of buttons', and then I subsequently say
that 'the second <div> in my document is a toolbar', then it is
legitimate to act as if the second <div> in my document has a property
of 'collection of buttons'.

My argument is that to deduce this set of additional statements from
@role is a step too far, and is more than was ever intended with
@role. We can certainly safely say 'the second <div> in my document
_is playing the role_ of a toolbar on this page'. Here we are simply
saying something about the 'intent' of the mark-up, or its purpose,
and the following triples capture that:

  <_:a> xh:role wai:toolbar .

But that is a world away from saying that the <div> we are dealing
with is *indistinguishable* from a wai:toolbar, which is what this
means:

  <_:a> rdf:type wai:toolbar .

The thing is we don't lose anything from not defining this as
rdf:type, and we gain a lot. By only saying that something is 'playing
the role of', we allow other systems to infer what they think is
appropriate about those roles. ARIA is a case in point; it has a set
of statements that are being made about certain resources. But we do
lose something if we say that @role="wai:toolbar", because that means
that the <div> is now an actual, real-live toolbar, and that will
invariably be incorrect or meaningless.

So in my view, if we want a shorthand for rdf:type, it must be either
@class or a new attribute.

Regards,

Mark

-- 
  Mark Birbeck, formsPlayer

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

  standards. innovation.
Received on Thursday, 5 July 2007 13:42:36 GMT

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