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Re: Are *relative* URIs as namespace nemes considered harmful?

From: James Clark <jjc@JCLARK.COM>
Date: Tue, 23 May 2000 19:46:21 +0700
Message-ID: <392A7D9D.C4146B8B@JCLARK.COM>
To: David Carlisle <davidc@nag.co.uk>
CC: timbl@w3.org, xml-uri@w3.org
David Carlisle wrote:
> 
> > That's not the problematic case.  The problematic case is when you have
> > two URI references that are identical when compared as strings but refer
> > to different resources (because they have different base URIs).
> 
> I don't understand why this is a problem.
> If I took the above quote out of this namespace thread and stuck it in a
> thread about the merits of using the HTML <a> element. Then in what way
> would it be diferent. The href="foo.html" is the same string but refers
> to different resources (because they have different base URIs).

If I have a low level layer that doesn't make a distinction between two
namespace names even though the namespace names identify different
resources, it will be difficult to build on top of this a higher level
layer that uses the namespace name directly to access the resource,
because it will be ambiguous what the resource associated with a
namespace name is.

The other way around isn't a problem.  If a low-level layer says
"http://www.w3.org/" and "http://WWW.W3.ORG/" are distinct, then there's
still a well-defined mapping from namespace names to resources that can
be used by higher level layers.

In general, a higher level layer can easily identify things that lower
level layers distinguish, but it's awkward for a higher level layer to
distinguish things that a lower level layer identifies.

James
Received on Tuesday, 23 May 2000 08:50:03 UTC

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