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Re: Fwd: I-D ACTION:draft-daigle-uri-std-00.txt

From: Dan Connolly <connolly@w3.org>
Date: Thu, 07 Sep 2000 08:54:03 -0500
Message-ID: <39B79DFB.6C9AEEDA@w3.org>
To: Miles Sabin <msabin@cromwellmedia.co.uk>
CC: xml-uri@w3.org
Miles Sabin wrote:
> 
> Simon St.Laurent wrote,
> > I think the 'rest of us' might well benefit from clearer
> > distinctions between URIs and the resources they identify,
> 
> But Simon, that's a pretty tall order, because there's no
> end to the number of distinct resources a URL (nb. UR*L*) might
> locate.

Not so: every URL is a URI[1]; every URI identifies exactly
one resource[2]; hence every URL identifies exactly one resource.

[1] The
   term "Uniform Resource Locator" (URL) refers to the subset of URI
   that identify resources via a representation of their primary access
   mechanism (e.g., their network "location"), rather than identifying
   the resource by name or by some other attribute(s) of that resource.

[2] "An identifier is an object that can act as a reference to
         something that has identity."

http://www.ietf.org/rfc/rfc2396.txt

> John Cowans example (I forget the URL, it was a time-
> server of some sort) was pretty good. Does that URL identify
> entities (particular sequences of bits on any given occasion),

no; those entities represent the state of the resource
identified.

> transient HTML documents (again changing over time);

no.

> a
> persistent HTML document (but with parts which change over
> time); the current time in whereever; John's favourite page;
> John's favourite example; etc. etc. depending on how
> imaginative you are.
> 
> Given that the list of distinct resources is open ended, it's
> hard to see how anyone could hope to come up with a general
> account of their relationship with the URL which is less
> abstract than the one we already have.
> 
> URNs, or any other scheme which actually specifies identity-
> criteria, on the other hand, have a fair chance of being
> unequivocal.

Every URN is also a URI; hence they have the same relationship
to resources that URLs have: one URN identifies one
resource.

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Thursday, 7 September 2000 09:54:48 GMT

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