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

Re: Fixed base

From: Dan Connolly <connolly@w3.org>
Date: Tue, 20 Jun 2000 12:47:54 -0500
Message-ID: <394FAE4A.8CA53358@w3.org>
To: James Clark <jjc@jclark.com>
CC: xml-uri@w3.org
James Clark wrote:
> 
> [...]  Absolutizing namespace names
> relative to a fixed based such as "contextdependent:/" satisfies both
> these requirements. 
[...]
>  This makes the behaviour of xmlns="" not be an
> ugly special exception, but just a consequence on the normal rules on
> resolving relative URIs.

Not an exception? Please consider the following document,
with a base URI of http://purl.org/dc/notes :

	<html
		xmlns="http://www.w3.org/1999/xhtml"
		xmlns:dc="elements/1.1/">
	<head>
	<title>some notes on Dublin Core stuff</title>
	</head>
	<body>
	<p>In development of
	<a href="elements/1.1/">the dublin core vocabulary</a>,
	we discovered ...
	</p>
	</body>
	</html>

Clearly, the link points to
	http://purl.org/dc/elements/1.1/

This "fixed base" suggestion proposed that the dc prefix
be associated with
	contextdependent:/elements/1.1/

That certainly looks like an ugly special exception to me.
If namespace declarations use URI references, then
I think it's pretty intuitive to folks that have been
using the Web for a while that the dc
prefix is associated with the same thing that
the link points to, namely:
	http://purl.org/dc/elements/1.1/

To do otherwise is clearly an exception to the way URI references
have worked for the last 10 years. 

HTML's <base> and xml:base create exceptions too...
the URI spec allows for such exceptions
on a per-mime-type basis (5.1.1. Base URI within Document Content),
so we could specify that this is how text/xml, applicaiton/xml
etc. work, if we wanted to.

Ugly is a matter of taste... I think making a special case
for namespace declarations is ugly. I don't see any motivation
for it (other than the fact that there are
implementations that don't grok relative URI references
at all, which I don't find compelling.)

I think HTML <base> is ugly, but at least
it affects all URI references in the document the same
way. xml:base is motivated by the case of
canonicalizing a multi-entity document, so that
you can express an element's base URI when
you copy it out of context.


-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Tuesday, 20 June 2000 13:49:35 UTC

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