W3C home > Mailing lists > Public > xml-uri@w3.org > September 2000

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

From: Dan Brickley <danbri@w3.org>
Date: Thu, 7 Sep 2000 10:45:43 -0400 (EDT)
To: Dan Connolly <connolly@w3.org>
cc: Miles Sabin <msabin@cromwellmedia.co.uk>, xml-uri@w3.org
Message-ID: <Pine.LNX.4.21.0009071026290.3018-100000@tux.w3.org>
On Thu, 7 Sep 2000, Dan Connolly wrote:

> 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

The text you cite, [2], leaves open the question of whether the
'something' that is referenced may differ over time. At any tick of the
clock, the identifier 'can' act as a reference to some thing; as time
passes and the world changes, it might subsequently fail to refer, or pick
out a different thing-with-identity.

This seems to be one of the various factors contributing to
confusion; while "every URL identifies exactly one resource" might be true
at any point in time, when people aggregate metadata about these
URIs/resources that spans several years, it isn't clear what the story is.

> > 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.

I believe there's a good case to be made for modeling these entities as
resources too. They're *not* the resource named by the URI, but something
else related to the named resource. We could usefully name the
relationship that holds between these entities and the more abstract
resources that they're manifestations/rendings of.
This way we could talk about them using any frameworks for resource
description we happen to have lying around...

Received on Thursday, 7 September 2000 10:45:49 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 6 January 2015 20:32:44 UTC