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RDF concepts

From: Jeremy Carroll <jjc@hpl.hp.com>
Date: Fri, 25 Oct 2002 07:26:17 +0200
To: w3c-rdfcore-wg@w3.org
Message-Id: <200210250726.17359.jjc@hpl.hp.com>


The version for review is ready; although I have not allowed Graham a chance 
to check over my latest changes (we have discussed the essential direction of 
these changes).

The current URL is:

http://sealpc09.cnuce.cnr.it/jeremy/RDF-concepts/2002-10-25/rdf-concepts.html

I expect Graham will want to copy it onto his site -
(a tar ball for you, with the this version URL fixed is:
http://sealpc09.cnuce.cnr.it/jeremy/RDF-concepts/2002-10-25.tgz
)
After he has done this, we should copy something to the archive.

My release notes, over and above the version Graham circulated last week are 
as follows:

- *all* literals are typed
- two new predefined types for what were previously untyped literals.
- literal is a pair (datatypeURI, lexical form)
    - lexical form is also a pair (string, language-identifier)
- datatype mappings (see section 2.4.4) can be from string=>value or from 
lexical form=>value


I believe I have slightly overstepped the appropriate editorial freedom, and I 
am prepared to backpeddle if the WG is unhappy with where I have gone.

Rationale for change to all typed literals:
- language id in typed literals, appeared to be the path to consensus at last 
telecon
- all three forms of literal then were very similar, the change to making them 
all typed is a rationalization
- this change has been suggested some times on the e-mail list [1], [2], with 
no explicit opposition
- the two most extensive external reviews of the abstracrt syntax in its first 
WD from TimBL [3] and Massimo [4] both suggest changes along these lines 
(neither of them felt confortable with the status given the XML literals).

 [1]
http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2002Sep/0196.html
[2]
http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2002Oct/0223.html
[3]
http://www.w3.org/2002/07/29-rdfcadm-tbl.html
[4]
http://lists.w3.org/Archives/Public/www-rdf-comments/2002JulSep/0165.html


The principle risks is:
- removing the langauge identifier from typed literals is now harder, if the 
call to include them was in error.
Two possible reasons why it might be in error are locale vs langauge 
confusion, and XSD conformance. I have tried to phrase the document to show 
appropriate deference to these concerns.

Minor advanatges:
+ it is now clearer what an n-triple doc with an ill-formed XML literal means
+ model theory will be more uniform

Minor disadvantges:
+ syntactic constructs using the two new datatypes as explicit rdf:datatype 
are somewhat peculiar.

Todo:
some schema declarations for datatyping.
I guess the two new datatypes are subclassof rdfs:Literal

Jeremy
Received on Friday, 25 October 2002 01:28:20 EDT

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