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Re: Denotation of XMLLiterals: poll

From: Graham Klyne <gk@ninebynine.org>
Date: Thu, 07 Aug 2003 12:44:00 +0100
Message-Id: <>
To: Brian McBride <bwm@hplb.hpl.hp.com>, rdf core <w3c-rdfcore-wg@w3.org>

At 12:29 06/08/03 +0100, Brian McBride wrote:

>It seems that there is some concern about XMLLiterals denoting octet 
>sequences.  As I understand things, RDFCore doesn't feel strongly that the 
>denotation MUST be octet sequences.  Pat has layed what we really care 
>about in:
>I suggest we accept Pat's suggestion and reconsider the denotation of 
>XMLLiterals.  I have seen three suggestions, as I recall:
>  A) be a bit vague about XMLLiterals really are - just define their 
> essential properties
>  B) have them denote XPATH nodesets
>  C) have them denote a pair (uri, lex form), where uri is the uri of 
> rdf:XMLLiteral.
>Concern has been expressed about A being to vague.  Others have responded 
>saying thats normal - integers are defined in terms of their properties.
>Concern has been expressed that XPATH nodesets are too vague, we don't 
>really know that they are and are thus no better than A, but are in some 
>way worse.  Cannonicalization does define an equality relation on them
>I have heard a private concern expressed about C, that if we did that, 
>shouldn't we treat all datatypes that way.  Further, that this does 
>guarantee that there are no other ways of denoting the same pair with 
>another, posibly user defined datatype.
>How do we choose?  If you have a preference and rationale, it would be 
>good hear it.

I agree that the choice of octet sequences is probably confusing.  In that, 
I understood we were simply following an existing spec.

I'm not sure that I follow the concern with (C):  XML is an inherently 
character-sequence-based format, so why not use a form of denotation that 
contains that sequence.  To do that for, say, numbers is unhelpful and 
unnecessary IMO (and I believe has led to some shortcomings in XML schema 
datatype treatment of numbers).

In particular, the form (C) asserts precisely the condition that Pat 
requires for the semantics: a 1:1 correspondence between lexical and 
denoted forms.

Another advantage of (C), it seems to me, is that it may make it easier to 
achieve something approaching the unification between plain literals and 
XML literals that Martin desires:  it would be a relatively easy for an 
application to interpret a sequence of characters S in a context where text 
is expected to be equivalent to (rdf:XMLLiteral,S).


Graham Klyne          _________
GK@ninebynine.org  ___|_o_o_o_|_
(nb Helva)       ~~~~~~~~~~~~~~~~~~   @Cliveden, River Thames
Received on Sunday, 10 August 2003 08:00:24 UTC

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