Re: Last Call comments on RDFa Core (Issue-68)

On Dec 13, 2010, at 12:19 , Harry Halpin wrote:

>> 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:
>> 
> 
> I am more than aware of de dicto and de re distinctions. For a long
> explanation of why this preoptimizing around use/mention distinctions is a
> bad idea, please read this paper by myself and Pat Hayes [1].
> 
> However in general that URIs are used to refer to and access resources. An
> image URI or a webpage are really resources in the same way as magical
> Semantic Web URIs that supposedly
> 
> To my knowledge, I have not seen a single halfway convincing usecase where
> there is a reason why you would want to 'mention' a URI, i.e. refer to it
> as a literal or xsd string.  If in general, you have a string of
> characters that appear to be URI, you may want to use it - i.e. access it
> using http - or refer to using RDF, whether or not it is the URI for Dan
> Brickley himself or his webpage. Whether upon encountering a URI you use
> it or refer to it with RDF should be in the hands of the end user, not
> told to you by RDFa syntax.
> 
> If the entire reason for this premature optimization is based on a
> distinctly idiosyncratic metaphysics...a distinction that TimBL has agreed
> can not in general be coherently explained...then I see no reason why the
> RDFa WG should punish end users in order to maintain this distinction by
> making them choose different @attributes based on this distinction.
> 
> As it is also particularly seems self evident that endusers already have
> trouble understanding any supposed distinctions here and are already using
> URIs where literals should be and vice versa anyways. So pave the cowpaths
> here rather than upholding a likely faulty understanding of philosophy of
> language.
> 
> [1]
> http://www.ibiblio.org/hhalpin/homepage/publications/indefenseofambiguity.html
> 
>>        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>
>> 
>> 
> 


----
Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
mobile: +31-641044153
PGP Key: http://www.ivan-herman.net/pgpkey.html
FOAF: http://www.ivan-herman.net/foaf.rdf