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Re: Last Call comments on RDFa Core

From: Toby Inkster <tai@g5n.co.uk>
Date: Mon, 13 Dec 2010 10:49:13 +0000
To: Ivan Herman <ivan@w3.org>
Cc: Harry Halpin <hhalpin@w3.org>, public-rdfa-wg@w3.org
Message-ID: <1292237353.5556.75.camel@ophelia2.g5n.co.uk>
On Mon, 2010-12-13 at 10:49 +0100, Ivan Herman wrote:
> I believe Toby's point is a little bit different. For all the reasons
> you cite Facebook has decided to use a vocabulary whereby the objects
> are all literals. That is their right, and they use RDFa consistently
> in this sense.

Yes, but further I was also trying to say that if I were designing a
property like og:url I'd design it to take a literal value - not for
pragmatic reasons, but because it makes sense.

When you use a URI in the subject, predicate or object position of a
triple, you're not really taking about the URI, you're talking about the
resource identified by the URI. When you need to talk about the URI
itself, and not the resource identified by it, you need to use a literal
(or, to get around RDF's literal subject restriction, a blank node which
is owl:sameAs the literal).

<http://en.wikipedia.org/wiki/Use–mention_distinction> is a good
explanation of the distinction. For a less dry take on it though, I'll
call upon the late, great Charles Lutwidge Dodgson:

        Alice was walking beside the White Knight in Looking Glass Land.
        	"You are sad." the Knight said in an anxious tone: "let me sing
        you a song to comfort you."
        	"Is it very long?" Alice asked, for she had heard a good deal
        of poetry that day.
        	"It's long." said the Knight, "but it's very, very beautiful.
        Everybody that hears me sing it - either it brings tears to
        their eyes, or else -"
        	"Or else what?" said Alice, for the Knight had made a sudden
        pause.
        	"Or else it doesn't, you know. The name of the song is called
        'Haddocks' Eyes.'"
        	"Oh, that's the name of the song, is it?" Alice said, trying to
        feel interested.
        	"No, you don't understand," the Knight said, looking a little
        vexed. "That's what the name is called. The name really is 'The
        Aged, Aged Man.'"
        	"Then I ought to have said 'That's what the song is called'?"
        Alice corrected herself.
        	"No you oughtn't: that's another thing. The song is called
        'Ways and Means' but that's only what it's called, you know!"
        	"Well, what is the song then?" said Alice, who was by this time
        completely bewildered.
        	"I was coming to that," the Knight said. "The song really is
        'A-sitting On a Gate': and the tune's my own invention."

-- 
Toby A Inkster
<mailto:mail@tobyinkster.co.uk>
<http://tobyinkster.co.uk>
Received on Monday, 13 December 2010 10:50:03 UTC

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