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RE: URIs / URLs

From: Lee Jonas <lee.jonas@cakehouse.co.uk>
Date: Thu, 12 Apr 2001 14:45:20 +0100
Message-ID: <51ED29F31E20D411AAFD00105A4CD7A770EE@zingiber.cakehouse.co.uk>
To: "'Charles McCathieNevile'" <charles@w3.org>, Lee Jonas <lee.jonas@cakehouse.co.uk>
Cc: RDF Interest <www-rdf-interest@w3.org>
Charles McCathieNevile [mailto:charles@w3.org] wrote:

>On Thu, 12 Apr 2001, Lee Jonas wrote:
>
[snip]
>
>  It is a fundamental aspect of the way URLs are defined to be used.  They
>  *locate* (note I did not say *identify*) representations (snapshots of
>  state) of underlying resources, not the resources themselves.  When
>  resources change, new representations may appear at the same and/or
>  different locations.  The only way RDF could satisfactorily deal with
this
>  is if it described the resources directly by using URN identifiers, which
>  could be subsequently mapped to a URL locating an appropriate
>  representation.
>
>I think this is where we get to the real nub of the problem. I do not agree
>that a UR* locates something. It identifies it. The Web provides a way of
>getting something where the identifier is a URI (and of putting something
at
>a location that can be found, if it has a URI identifier). That something
can
>either be the thing itself, or some information about the thing. And that
>depends on the semantics of the identifier, not the syntax. A new syntax
>doesn't change that, and a syntax that says "use a URI to work out how to
get
>another kind of identifier" doesn't seem to add anything except a layer of
>complexity.
>
>cheers
>
>Charles

To be more clear about what I said, of course URIs (both URLs and URNs)
identify resources.  I tried to make it clear that URLs identify the
resource, not the representation.

The point I am trying to make is that URLs identify resources by specifying
the network location of a representation.

Consider the "Document Object Model (DOM) Level 3 Events Specification"
Working Draft.

It is a single resource available in 2 versions:
1) version "20010410"
2) version "20000901"

and with 3 representations:
A) http://www.w3.org/TR/2001/WD-DOM-Level-3-Events-20010410
B) http://www.w3.org/TR/2000/WD-DOM-Level-3-Events-20000901/ 
C) http://www.w3.org/TR/DOM-Level-3-Events

If I make RDF assertions about C) I am referring to the "latest" version in
perpituity, if I make assertions about A) I am referring to a specific
version.  What if I want to make assertions about all current and future
versions of "Document Object Model (DOM) Level 3 Events Specification"?

It seems that identifying it by name (i.e. URN) is a good option.

regards

Lee
Received on Thursday, 12 April 2001 09:45:39 GMT

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