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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 12:26:52 -0500
Message-ID: <39B7CFDC.783E9DC1@w3.org>
To: John Cowan <jcowan@reutershealth.com>
CC: "xml-uri@w3.org" <xml-uri@w3.org>
John Cowan wrote:
> 
> Dan Connolly wrote:
> 
> > Not so: every URL is a URI[1]; every URI identifies exactly
> > one resource[2]; hence every URL identifies exactly one resource.
> 
> [snip]
> 
> > [2] "An identifier is an object that can act as a reference to
> >          something that has identity."
> >
> > http://www.ietf.org/rfc/rfc2396.txt
> 
> I have no problem with this.  However, it is not clear to me
> why distinct URLs must refer to distinct resources.

Who said they must?

The specs don't rule one way or the other on question
of whether distinct URIs always denote distinct resources,
as far as I know.

It's pretty clear to me that
	http://www.w3.org/
and
	http://www.w3.org:80/

denote the same resource.

In your example...

>  My contention
> is that
> 
>         ftp://ftp.unicode.org/Public/MAPPINGS/ISO/8859-1.TXT
> 
> and
> 
>         http://www.unicode.org/Public/MAPPINGS/ISO/8859-1.TXT
> 
> represent the same *resource*, not merely the same entity body.
> Both URIs refer to the mapping between the Unicode and ISO 8859-1
> character sets.
> 
> Or at least that this could be so, if the Unicode Consortium said
> it was so.

Hmm... if two things are identical, they're identical
in every possible respect. If unicode.org turned off
its ftp server and left its http server running one day,
then you could observe a difference between what
the two URIs above denote. That suggests to me that
the resources are distinct.

But perhaps not... perhaps a "connection refused" isn't
an observation of the resource, but a *failure* to
observe the resource. And it's generally not sound
to conclude anything (including that X!=Y) from
a lack of information.


-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Thursday, 7 September 2000 13:28:12 GMT

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