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Re: Test cases for literal equality?

From: Dan Connolly <connolly@w3.org>
Date: 03 Apr 2003 16:44:09 -0600
To: Dave Beckett <dave.beckett@bristol.ac.uk>
Cc: Graham Klyne <gk@ninebynine.org>, w3c-rdfcore-wg@w3.org
Message-Id: <1049409849.29206.33.camel@dirk.dm93.org>

On Tue, 2003-04-01 at 09:13, Dave Beckett wrote:
> >>>Dan Connolly said:
> > On Thu, 2003-03-13 at 05:32, Dave Beckett wrote:
> > > xsd:string is a datatype in the XSD specification and from what I
> > > recall, RDF doesn't use it - no RDF literal is an xsd:string nor has
> > > one as a part,
> > 
> > If people are going to continue to say things like this about
> > literals in RDF vs. XML Schemas, I guess I'll have to take
> > a much stronger position on=20
> > http://www.w3.org/2001/sw/RDFCore/20030123-issues/#danc-02
> > 
> > On the contrary, *every* RDF literal is either an xsd:string
> > or has one in part.
> 
> The concepts WD does not say this explicitly.

And so...?

> > Proof: "The =B7value space=B7 of string is the set of finite-length
> > sequences of characters"
> >  -- http://www.w3.org/TR/xmlschema-2/#string
> > 
> > "A literal in an RDF graph contains three components called:
> > 
> >       * The lexical form being a Unicode [UNICODE] string in Normal Form
> >         C [NFC]."
> >  -- http://www.w3.org/TR/rdf-concepts/#section-Literals
> 
> 
> And are all XSD strings in Normal Form C?  
>   http://www.w3.org/TR/xmlschema-2/#string
> doesn't seem to say that.

Why is that relevant? I think you've got
your quantifiers mixed up.


> It's clear what a literal in an RDF graph is from the above
> definition.  Although an xsd:string would be capabable of
> transporting (encoding?) the lexical form part of RDF literal, there
> would would be requirement that it was in NFC.

Well, yes, it would as a matter of course remain in NFC.
Again, how is that relevant?

> > 
> > >  although the lexical form definition is compatible
> > > with it.  A quick grep in the concepts WD confirms this as far
> > > as I can tell.  So we don't need to test xsd:string comparisons.
> > 
> > I think that's a counter-productive direction to take.
> 
> If we added such a (normative) dependency on all of RDF to xsd:string
> and hence the XML Schema RECs, I worry what that would imply.

Why worry about simple facts about sequences of unicode characters?

>   Would all implementors need an "XML schema implementation" of some sort?

No more than they already have.

>   Would the RDF Semantics WD have to deal with the semantics of XSD?

Again, no more than they already do. Both XSD and RDF involve
the concept of a sequence of unicode characters.

> Dave
-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Thursday, 3 April 2003 17:44:17 EST

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