W3C home > Mailing lists > Public > uri@w3.org > September 2001

Re: Excess URI schemes considered harmful

From: Michael Mealling <michael@neonym.net>
Date: Tue, 25 Sep 2001 17:20:56 -0400
To: Mark Baker <distobj@acm.org>
Cc: Rob Lanphier <robla@real.com>, uri@w3.org
Message-ID: <20010925172055.K6341@bailey.dscga.com>
On Tue, Sep 25, 2001 at 02:52:50PM -0400, Mark Baker wrote:
> > Implementations which rely on a URI encoding of a media type should not be 
> > required to dereference a URI to determine equivalency.  Redirects assume 
> > dereferencing.
> There's different degrees of equivalency at play here.
> It is the case that if two HTTP URIs are equal, that they necessarily identify
> the same resource (also see RFC 2616 sec 3.2.3).  It is not the case that if 
> two HTTP URIs are *not* equivalent (even modulo 2616/3.2.3), that they do 
> *not* represent the same resource.  The only way to determine whether two 
> non equivalent HTTP URI represent the same resource latter is to have 
> authoritative info about that equivalence (or lack thereof).  One way for 
> that authoritative info to be communicated is with an HTTP redirect.
> Even the current CTURI draft has the latter problem, as the encoding is not
> canonical.

This is indeed the case with _all_ URIs. Equivalence of resources across 
schemes is iff the URIs are lexicographically equal. URIs themselves
express no other type of equivalence other than that since equivalence
is always application specific and more often than not is also context
specific. Unless you have some application specific knowledge talking
about equivalence of Resources is a very dangerous and, IMNSHO, simply
a Bad Thing To Do...


Michael Mealling	|      Vote Libertarian!       | urn:pin:1
michael@neonym.net      |                              | http://www.neonym.net
Received on Tuesday, 25 September 2001 17:25:46 UTC

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