W3C home > Mailing lists > Public > www-tag@w3.org > January 2003

Re: Why URIs in RDF?

From: Graham Klyne <GK@ninebynine.org>
Date: Wed, 15 Jan 2003 11:37:19 +0000
Message-Id: <5.1.0.14.2.20030115111827.00ab3750@127.0.0.1>
To: Sandro Hawke <sandro@w3.org>
Cc: www-tag@w3.org

At 11:35 PM 1/14/03 -0500, Sandro Hawke wrote:
>But ... both HTTP and RDF use URIs!  Why is that?  We know why HTTP uses
>URIs, but what purpose do URIs serve in RDF?
>
>The RDF Concepts draft [1] says:
>
>     The expressive power of RDF corresponds to the
>     existential-conjunctive (EC) subset of first order logic [Sowa].
>
>     Through its use of extensible URI-based vocabularies, RDF provides
>     for expression of facts about arbitrary subjects; i.e. assertions
>     of named properties about specific named things. A URI can be
>     constructed for any thing that can be named, so RDF facts can be
>     about any such things.
>
>That second paragraph is crucial if vague.  Try actually communicating
>in first-order logic (let alone the EC subset) and you immediately
>realize that you and your audience must share an interpretation (a
>mapping of identifiers to the things they identify), or at least some
>of it.  An automated reasoner doesn't need to know anything about your
>interpretation, but your audience sure does.

I find myself fully agreeing with Roy about this.  I don't see anything 
broken here, hence nothing to be fixed.   (Apart from that the wording you 
quote still needs to be improved.)

I'm beginning to think that your assumption that people differ from 
automated reasoners in that they *do* need to know all about the intended 
denotation of a URI may not be valid.

Like the blind men and the elephant [1], sometimes all that matters, even 
to people, is the actual manifestations (representation) of a resource.

So it may matter less what the URI "http://www.w3.org/Consortium/" actually 
denotes than what representations it delivers, or what is asserted about 
it.  The representations and assertions provide partial knowledge which may 
or may not be sufficient to underpin communicate about whatever it is that 
is denoted.

Thus, there may be an arbitrary number of denotations of 
"http://www.w3.org/Consortium/" that satisfy all the observed data, and any 
may do.  What does it matter if it's a document or an organization?

"Here be elephants"

#g
--

[1] http://www.cs.princeton.edu/~rywang/berkeley/258/parable.html
     http://www.wordfocus.com/word-act-blindmen.html


-------------------
Graham Klyne
<GK@NineByNine.org>
Received on Wednesday, 15 January 2003 09:22:35 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Thursday, 26 April 2012 12:47:15 GMT