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RE: Re[2]: Summary: Section 2: What does a URI identify?

From: Williams, Stuart <skw@hplb.hpl.hp.com>
Date: Tue, 19 Mar 2002 19:33:57 -0000
Message-ID: <5E13A1874524D411A876006008CD059F192A47@0-mail-1.hpl.hp.com>
To: "'Jonathan Borden'" <jonathan@openhealth.org>
Cc: Paul Grosso <pgrosso@arbortext.com>, www-tag@w3.org, Chris Lilley <chris@w3.org>, "McBride, Brian" <bwm@hplb.hpl.hp.com>
Hello Jonathan,

> -----Original Message-----
> From: Jonathan Borden [mailto:jonathan@openhealth.org]
> Sent: 19 March 2002 17:02
> To: Chris Lilley; Brian McBride
> Cc: Paul Grosso; www-tag@w3.org
> Subject: Re: Re[2]: Summary: Section 2: What does a URI identify?

> RDF has been around as a Recommendation alot longer than XML Base, so who
> at fault? Did XML Base ensure that it covered the very real needs of RDF?

I don't think the XML Base recommendation is the issue here. XML Base gives
a means to specify/determine the base URI to be used when resolving a
relative URI. It is RFC2396 (which pre-dates the RDF recommendation) that
makes '#foo' a "same document reference" and establishes that a base URI is
not applied when resolving a "same document reference".

I came across this when thinking about the application of XML Base in the
context of the SOAP encoding style. I found myself asking how would I
'turn-off' a base URI established through the use of xml:base so that I
could ensure that a fragment only URI reference could very definitely be
interpreted as relative to the current document. If you like I was looking
for the XML base analog of unsetting a default namespace ( xmlns="" ) for
some inner scope within a document. I couldn't find a mechanism to do that
in the XML Base document - which may be a problem in other contexts.

However, in delving into RFC 2396, found pretty clear that '#foo' is not a
relative URI reference, and hence is not resolved with respect to an XML
base. Section 4.1 of RFC 2396 is also pretty clear:

   The semantics of a fragment identifier is a property of the data
   resulting from a retrieval action, regardless of the type of URI used
   in the reference.  Therefore, the format and interpretation of
   fragment identifiers is dependent on the media type [RFC2046] of the
   retrieval result. 

> Would you be happier if RDF defines: rdf:base="URI" that is just like
> xml:base but is defined to behave the way RDF intends? Would that better
> serve the needs of the Web?

I think, as Brian points out, at least as far as labeling RDF nodes it is
possible to avoid RDF's idiomatic use of fragment ids.

> Perhaps the authors of RFC 2396, particularly those which are on the TAG,
> can offer us some guidance as to whether RDF has it right or wrong.

I too would be interested in their comments.

> Short of that, why is _your reading_ better than _my reading_ particularly
> when we both have different applications e.g. HTML vs. RDF, in mind.

Yep.. I guess we have, "What was intended?" and "Does what is written
clearly articulate what was intended?"

To be honest, I find RFC2396 pretty clear... but that is just my reading of

> Moreover I don't see (at all) why the RDF handling of rdf:ID="foo" at all
> harms HTML or any other application that does not concern itself with RDF.
> Jonathan

Best regards

Stuart Williams
Received on Tuesday, 19 March 2002 14:34:41 UTC

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