W3C home > Mailing lists > Public > www-tag@w3.org > March 2002

Re: "canonical" URIs

From: Mark Baker <distobj@acm.org>
Date: Tue, 19 Mar 2002 21:19:03 -0500 (EST)
Message-Id: <200203200219.VAA29454@markbaker.ca>
To: david.orchard@bea.com (David Orchard)
Cc: www-tag@w3.org

> TAG members,
> I don't see URI comparison officially listed as a TAG issue.  I'd like
> Joseph/Stephen's issue added to the TAG issues list.
> Equivalence rules for URIs are defined by the URI scheme.

Not all of them.  DAML can be used to assert equivalence about any
resources.  HTTP redirection can be used for the same purposes, for
resources other than those using the HTTP URI scheme.

I recall a TimBL message where he enumerated the possible layers of
equivalence.  Can't find it though.

>  HTTP has a
> section on URI comparison.
> However, XML does not have a default comparison function for the XML Schema
> anyURI data type.  I think a reasonable approach would be to say that the
> default comparision function for anyURI is to use the HTTP URI comparison
> algorithm, but that it is overridable by any scheme.

Why is it any of XML's business?  RFC 2396 already says everything that
needs saying; that syntactic comparison is a function of the URI scheme.
If you don't recognize the URI scheme, you can only compare for an exact

Of course, anyURI is a URI reference, not a URI.  In order to compare
two URI refs that aren't syntactically identical, I believe you would
have to dereference them, as the media type is presumably the authority
on whether the frag ids are case sensitive or not.  Oh joy. 8-/

Mark Baker, Chief Science Officer, Planetfred, Inc.
Ottawa, Ontario, CANADA.      mbaker@planetfred.com
http://www.markbaker.ca   http://www.planetfred.com
Received on Tuesday, 19 March 2002 21:14:15 UTC

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