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Re: XML literals

From: Frank Manola <fmanola@mitre.org>
Date: Fri, 01 Aug 2003 09:37:50 -0400
Message-ID: <3F2A6D2E.4040907@mitre.org>
To: Patrick Stickler <patrick.stickler@nokia.com>
CC: Brian_McBride <bwm@hplb.hpl.hp.com>, Jeremy Carroll <jjc@hpl.hp.com>, Graham Klyne <gk@ninebynine.org>, ext pat hayes <phayes@ihmc.us>, w3c-rdfcore-wg@w3.org, "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>

Let me also suggest that we carefully consider how we're going to 
explain this stuff in the Primer so people won't totally avoid using 
XMLLiterals (unless that's the idea!) due to not being able to figure 
out what the resulting RDF triples will be.  (The point is, we need to 
explain this so they won't think they have to).

--Frank

Patrick Stickler wrote:

>  
> 
>     ----- Original Message -----
> 
>     From: ext pat hayes <mailto:phayes@ihmc.us>
> 
>     To: Brian_McBride <mailto:bwm@hplb.hpl.hp.com> ; Jeremy Carroll
>     <mailto:jjc@hpl.hp.com> ; Graham Klyne <mailto:gk@ninebynine.org>
> 
>     Cc: w3c-rdfcore-wg@w3.org <mailto:w3c-rdfcore-wg@w3.org> ; Peter F.
>     Patel-Schneider <mailto:pfps@research.bell-labs.com>
> 
>     Sent: 01 August, 2003 06:41
> 
>     Subject: XML literals
> 
> 
>     Gentlemen:
> 
> 
>     I am completely sick of all these debates about XML literals.
> 
>      
> 
> Join the club ;-)
> 
>     Allow me to suggest a possible solution, along the lines suggested
>     by Peter, which will serve to resolve them without making any
>     substantial changes to the current RDF design and to everyone's
>     general satisfaction.  This is a wording change to the Concepts
>     document; I do not believe it amounts to any real change in our
>     current design, and may be easier to follow.
> 
> 
>     1. Concepts section 5.1 modified as follows (change starts at ***)
> 
>     .....
> 
> 
>     Such content is indicated in an RDF graph using a typed literal 
>     whose datatype is a special built-in datatype rdf:XMLLiteral , 
>     defined as follows.
> 
>     A URI reference for identifying this datatype
>     is http://www.w3.org/1999/02/22-rdf-syntax-ns#XMLLiteral .
> 
>     The lexical space is the set of all strings which:
>     are well-balanced, self-contained XML data [ XML ];
> 
>     correspond to exclusive Canonical XML (with comments, with empty
>     InclusiveNamespaces PrefixList )[XML-XC14N] ;
> 
>     when embedded between an arbitrary XML start tag and an end tag form
>     a document conforming to XML Namespaces [XML-NS]
> 
>     ***
> 
>      
> 
> Fine so far (i.e. the unchanged bit ;-)
> 
>      
> 
>     The value space is some set of entities, called XML values, which is:
> 
>     disjoint from the lexical space
> 
>      
> 
> OK.
> 
>     disjoint from the value space of any XML schema datatype (refer XSD)
> 
>      
> 
> Debatable, and we should be careful about making this claim. Better to 
> say nothing
> 
> than something that may end up biting us later.
> 
>      
> 
>     disjoint from the set of Unicode character strings (refer Unicode)
> 
>      
> 
> Maybe.  
> 
>  
> 
>     in 1:1 correspondence with the lexical space.
> 
> Right.
> 
>     The exact nature of XML values is not specified.
> 
>  
> 
> No. This bothers me. Alot.
> 
>  
> 
> It is our responsibility to define what the values of XML Literals are.
> 
> It's *our* datatype, and no'one else should have to define it,  or guess.
> 
>  
> 
> Taking this position is irresponsible, at best.
> 
>  
> 
> We can either take the present position, whereby XML literals have
> 
> lexical forms constituting canonical XML fragments encoded as
> 
> Unicode strings and values constituting the lexical form in UTF-8.
> 
>  
> 
> Or, if that bothers I18N, we could take a position whereby XML literals
> 
> have  lexical forms constituting canonical XML fragments encoded as
> Unicode strings and values corresponding to infosets.
> 
>  
> 
> This latter option has always struck me as the correct solution, as
> 
> after all, that's really what we're talking about, XML documents,
> 
> not just uninterpreted sequences of characters, and is not the
> 
> very point of the Infoset spec to provide a consistent interpretation
> 
> of sequences of characters in terms of XML?
> 
>  
> 
> I've never understood the opposition to having a value space
> 
> consisting of infosets. I wish someone would tell me what significant
> 
> problem or issue I'm missing...
> 
>  
> 
> --
> 
>  
> 
> At the very least, we *must* define what the value space of rdfs:XMLLiteral
> 
> is.  We can't simply cop out.
> 
>  
> 
> Patrick
> 
>  
> 


-- 
Frank Manola                   The MITRE Corporation
202 Burlington Road, MS A345   Bedford, MA 01730-1420
mailto:fmanola@mitre.org       voice: 781-271-8147   FAX: 781-271-875
Received on Friday, 1 August 2003 09:14:19 EDT

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