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RE: Heads up: RFC2996bis, possible problem for RDF

From: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Date: Tue, 17 Feb 2004 15:30:36 +0100
To: "Graham Klyne" <gk@ninebynine.org>, "rdf core" <w3c-rdfcore-wg@w3.org>
Message-ID: <BHEGLCKMOHGLGNOKPGHDMEKGCCAA.jjc@hpl.hp.com>

This does not look disastrous to me.

In RDF URIrefs ending in # (i.e. with explicitly empty fragment) only
regularly occur as namespace names. All possible uses of such URIrefs
involve qnames which give them a non-emtpy fragment part.

The text in question

"URI producers and normalizers should omit a delimiter if the component it
delimits is empty"

uses a "should" not a "MUST", and is hence sufficiently weak.

We perhaps could suggest modifying the text:
[[

, with one exception: a double-slash delimiter indicating an authority
component should not be removed, even when the authority is empty, since
doing so can lead to misinterpreting the path.
]]
http://gbiv.com/protocols/uri/rev-2002/rfc2396bis.html#normalize-empty

to
[[
. A first exception is: a double-slash delimiter indicating an authority
component should not be removed, even when the authority is empty, since
doing so can lead to misinterpreting the path.
A second exception is: a common idiom in RDF/XML uses URI references with
empty fragments as XML namespace names.
]]

The overall normalization rules in section 6
http://gbiv.com/protocols/uri/rev-2002/rfc2396bis.html#comparison
inevitable create a many positive matches that are not honoured in RDF
concepts. Like XML namespaces we chose the simplest possible definition of
equality: string equality. The overall tone of section 6 ought to respect
such a choice.



Jeremy


> -----Original Message-----
> From: w3c-rdfcore-wg-request@w3.org
> [mailto:w3c-rdfcore-wg-request@w3.org]On Behalf Of Graham Klyne
> Sent: 17 February 2004 13:17
> To: rdf core
> Subject: Heads up: RFC2996bis, possible problem for RDF
>
>
>
> I've just reviewed:
>
>     http://gbiv.com/protocols/uri/rev-2002/rfc2396bis.html
> Modified: 16 February 2004 11:36:15
> Size: 167.42 KB (171437 bytes)
>
> Which has recently been "last called" in the IETF URI informal group in
> preparation for an IESG last-call request, per:
>    http://lists.w3.org/Archives/Public/uri/2004Feb/0082.html
>
> I am concerned that the empty component normalization rules may be
> troublesome for RDF.  My review comments are at:
>    http://lists.w3.org/Archives/Public/uri/2004Feb/0094.html
>
> The specific example raised is:
>
> [[[[
> Section 6.2.2.3:
> I'm concerned about empty component normalization:
> In RDF usage, the URIs:
>      http://example.org/
> and
>      http://example.org#
> would result in quite distinct resource identifiers, e.g. in:
>
> [[
> Triples of the Data Model in N-Triples Format (Sub, Pred, Obj)
>
> <http://www.w3.org/RDF/Validator/run/foo>
> <http://example.org/prop> "value" .
>
> The original RDF/XML document
>
> 1: <?xml version="1.0"?>
> 2: <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
> 3:   xmlns="http://example.org/">
> 4:   <rdf:Description rdf:about="foo">
> 5:     <prop>value</prop>
> 6:   </rdf:Description>
> 7: </rdf:RDF>
> ]]
>
> and
>
> [[
> Triples of the Data Model in N-Triples Format (Sub, Pred, Obj)
>
> <http://www.w3.org/RDF/Validator/run/foo>
> <http://example.org#prop> "value" .
>
> The original RDF/XML document
>
> 1: <?xml version="1.0"?>
> 2: <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
> 3:   xmlns="http://example.org#">
> 4:   <rdf:Description rdf:about="foo">
> 5:     <prop>value</prop>
> 6:   </rdf:Description>
> 7: </rdf:RDF>
> ]]
>
> (RDF triples generated by http://www.w3.org/RDF/Validator/)
>
> Are distinct RDF graphs, even though the URIs are equivalent under the
> normalization rules given.
> ]]]]
>
> #g
>
>
> ------------
> Graham Klyne
> For email:
> http://www.ninebynine.org/#Contact
>
>
Received on Tuesday, 17 February 2004 09:30:55 UTC

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