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Re: XML Base and XPath absolutizing of URIs

From: Paul Grosso <pgrosso@arbortext.com>
Date: Thu, 08 Jun 2000 17:35:55 -0500
Message-Id: <3.0.32.20000608173422.006b1198@pophost.arbortext.com>
To: "John Boyer" <jboyer@PureEdge.com>, "Joseph M. Reagle Jr." <reagle@w3.org>
Cc: "XML DSig" <w3c-ietf-xmldsig@w3.org>, <elm@east.sun.com>, <xml-uri@w3.org>, <www-xpath-comments@w3.org>, <www-xml-linking-comments@w3.org>, <Daniel.Veillard@w3.org>, <connolly@w3.org>
At 14:43 2000 06 08 -0700, John Boyer wrote:
>As you know there is a wonderful debate in the W3C community now about
>whether or not namespace URIs should be absolutized.  I'm not on the xml-uri
>list, but have mailed this anyway.  Perhaps you could consider posting this
>for me if it doesn't show up there.

It did show up, and I'm replying to all, but this cross posting
may quickly get unwieldy.  I'll try to be brief and address just
your XML Base issue.

>The newest XBase spec does not mention XPath in the list of affected
>specifications, but it is claimed that XBase is required by XLink, which
>relies on XPath.

XML Base merely defines a way in XML (analogous to what the <base> element
in HTML does for HTML files) to specify the value of the base URI per
section "5.1.1. Base URI within Document Content" in RFC 2396 [1].  It
says nothing--beyond normatively referencing 2396--about what you do
with the base URI.  As such, XML Base does not in any way affect XPath.

>The XPath Recommendation states that URIs are absolutized, but no mechanism
>for specifying the base URL is given.  

Not quite true.  In the same paragraph that it discusses absolutization,
it normatively references RFC 2396 which precisely defines absolutization.

>I need to know as soon as possible
>whether an erratum to XPath will be issued to state that XBase will be the
>way of doing it.  Alternately, will there be an erratum stating that XPath
>does not absolutize URIs?

I assume you are referring only to the absolutization of namespace URIs.
This is the big question of the moment.  But note that XML Base is
unaffected by the outcome.  XML Base is still useful for providing
a base URI for relative URIs that get absolutized, and the question
of whether namespace URIs are among those that (1) can be relative
and, if so, (2) get absolutized, does not change XML Base at all.

>It is very important to our dsig implementers, whose XPath implementations
>seem not to absolutize URIs.

Well, that is ironic and interesting information, since it's XPath
that says they do get absolutized and would need to be changed if
we decide not to absolutize them.  It sounds like you have more of
an issue with XPath and/or its (non-conforming) implementations,
but you don't have one with XML Base.

paul

[1] http://www.ietf.org/rfc/rfc2396.txt
Received on Thursday, 8 June 2000 18:36:40 GMT

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