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Re: Summary of strings, markup, and language tagging in RDF (resend)

From: Brian McBride <bwm@hplb.hpl.hp.com>
Date: 03 Jul 2003 12:24:25 +0100
To: pat hayes <phayes@ihmc.us>
Cc: rdf core <w3c-rdfcore-wg@w3.org>, jjc@hplb.hpl.hp.com, Martin Duerst <duerst@w3.org>
Message-Id: <1057231465.3048.85.camel@dhcp-91-136.hpl.hp.com>

On Thu, 2003-07-03 at 02:52, pat hayes wrote:

[...]

> 
> Since this issue seems to be so centrally important, and since our 
> design now appears to people like Martin to be so completely 
> brain-damaged, let me propose that we re-open this issue and change 
> our design slightly, 

Pat, thank you for this proposal (in the same sense of thank you as in
"thank you for slapping me about the face with a wet fish").

Please could you hold that thought for now.

My preferred approach to this discussion is first of all to determine
whether the simpler, and I suspect less controversial, solution of
reintroducing the wrapper would satisfy i18n so far as issue b) is
concerned, which I'm hopeful it would.

RDFCore can then decide whether to accept I18N's arguments that the
present design should be changed.  *If* they do, then they can decide
how best to address those requirements.

Can you live with that?

Brian 

The WG

> by reverting to an older design. The trouble 
> seems to arise from our insisting that XML literals are treated 
> uniformly with typed literals: so let us abandon that idea, in spite 
> of its being very neat, and revert to the state where the XML 
> literals as treated as a special syntactic case in the RDF graph, so 
> that there would be five kinds of literal: plain and XML with and 
> without lang tags, plus datatyped literals.
> 
> In detail, the proposal is as follows.
> 
> 1. There are five kinds of literal in an RDF graph, indicated in 
> Ntriples as follows:
> "string"  				plain
> "string"@tag  			plain plus lang tag
> "string"^^rdf:XMLLIteral  		XML
> "string"@tag^^rdf:XMLLiteral  	XML plus lang tag
> "string"^^foo:baz  			typed, where foo:baz is any 
> URI other than 'rdf:XMLLiteral'
> 
> Notice that the Ntriples way of indicating the XML case is just as it 
> is now, but thats just a syntactic decision to save work; 
> rdf:XMLLiteral isn't a datatype and XML literals are not typed 
> literals in this design, so the possibility of having lang tags in 
> its lexical space isn't going to cause any headaches..
> 
> 2. The semantic conditions on the first four are specified in the RDF 
> interpretations and spelled out in detail - exactly how I leave to 
> others to decide, but it seems to me that we could dispense with the 
> wrapper (since we don't need to include the lang tag in a value space 
> any more) and could just say that the XML case is treated 
> semantically just like the plain case, ie the XML literal denotes 
> itself (a piece of XML text, perhaps one conforming to Jeremy's 
> elaborate conditions in 
> http://www.w3.org/2001/sw/RDFCore/TR/WD-rdf-concepts-20030117/#section-XMLLiteral, 
> or such a piece of text plus a lang tag); this would simplify the RDF 
> MT, in fact.
> 
> 3. In RDF/XML, rdf:parseType="Literal" maps to an XML literal and any 
> enclosing lang tag in the XML document is incorporated into the @tag 
> in the RDF graph. This allows RDF/XML to not appear 
> XML-brain-damaged, since now
> 
> <rdf:Description xml:lang="en">
>    <foo:prop parseType="Literal">
>      <em>chat</em>
>    </foo:prop>
>    <foo:prop>chat</foo:prop>
> </rdf:Description>
> 
> parses into
> 
> _:x foo:prop "<em>chat</em>"@en^^rdf:XMLLiteral .
> _:x foo:prop "chat"@en .
> 
> 4. Regarding Martin's other beef, that some XML without any markup in 
> it is 'really' just plain text, this design also allows an RDF 
> application to deal with this reasonably sensibly, since that 
> identification amounts to just stripping off the ^^rdf:XMLLiteral 
> flag when the literal string has no XML markup in it. I would vote 
> against making that a valid RDF entailment in the semantics, but it 
> would be relatively easy for a small app to do this using simple 
> scripting on literals and still be a sensible semantic extension, 
> without getting into all the datatyping complexity.
> 
> It would be relatively trivial to make the corresponding changes to 
> the Semantics document for this design: I think the changes to 
> Ntriples would be simple. Concepts would need some re-wording in 
> sections 3.4 , 5 and 6; and maybe it would need section 5.1 being 
> relocated. The changes are all essentially editorial, however, since 
> every document has to treat XML literals as a special case already. 
> I'm not sure what the effect on Syntax or Primer would be, but I 
> think it would be relatively easy to tweak them. I havn't checked 
> test cases.
> 
> Pat
Received on Thursday, 3 July 2003 07:25:16 EDT

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