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Re: XQuery and RDF datatypes was: RDF specifications

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 05 Dec 2001 09:10:13 -0500
To: jborden@mediaone.net
Cc: www-rdf-interest@w3.org
Message-Id: <20011205091013Y.pfps@research.bell-labs.com>
From: "Jonathan Borden" <jborden@mediaone.net>
Subject: XQuery and RDF datatypes was: RDF specifications
Date: Tue, 4 Dec 2001 17:16:52 -0500

> Peter F. Patel-Schneider wrote:
> 
> > In fact, the XQuery Data Model supports precisely this interface, or
> > so I gather from my reading of the specification.
> 
> Perhaps you mean the XQuery 1.0 Formal Semantics (XQFS)
> http://www.w3.org/TR/query-semantics/ ? Or XML Schema Formal Description
> (XSFD) http://www.w3.org/TR/xmlschema-formal/ ?
> both are currently WD and are intended to _supercede_ XML Schema 1.0
> datatypes (just so we are clear about what we are discussing :-)

I was thinking of the XQuery 1.0 and XPath 2.0 Data Model, also in WD, at
http://www.w3.org/TR/query-datamodel/
and, in particular, an implementation of it, called galax.

> I thought we were discussing XML Schema datatypes, if you are instead
> talking XQuery algebra then I couldn't agree more on that value of
> incorporating this into RDF for several reasons (read on).

Nope, I'm talking about XML Schema datatypes.  As far as I know, XML Schema
datatypes are the only official way of putting datatype information in XML
documents.

[...]

> > My stance is quite simple.
> >
> > 1/ RDF should incorporate XML Schema datatypes.
> 
> I am not sure how RDF can 'incorporate' XML Schema datatypes alone. Do you
> mean that the RDF DT semantics should incorporate XSFD and/or XQFS? Or do
> you mean that RDF should incorporate the concepts of 'string' 'integer' and
> 'date'?

The model theory should incorporate, at least, XML Schema primitive
datatypes.  RDF/XML syntax should allow, at least, the specification of XML
Schema primitive datatypes, using the xsi:type construct.  (I would like to
go much further, of course.  I think that the natural place is to have the
input to RDF from XML syntax be the XQuery 1.0 and XPath 2.0 Data model.)

> > 2/ The XQuery data model provides a relatively easy interface to get the
> >    resultant typed literals into RDF.
> 
> yes! I strongly agree. Not only that but Jonathan Robie has shown me a
> _terrific_ example using XQuery on XML/RDF datasets -- yet one more reason
> why RDF++ ought keep close to XML++. XQuery is one of the most promising
> technologies I've seen come out of these efforts.

> > 3/ If semantic typing is needed, it can be done using a slightly modified
> >    version of the code in an implementation of the XQuery data model.
> >    (Basically, you need direct access to the part of the implementation
> >    that performs the lexical-to-value mapping for XML Schema datatypes.)
> 
> Careful, because there are known inconsistencies between XML Schema _1.0_
> and XSFD as well as XQFS (this is much of the _reason_ they were developed
> _after_ XML Schema 1.0 was specified). Hopefully the work of XSFD/XQFS will
> be incorporated into XSD 1.1.

Yes, it would be much better if the XML-related stuff was in a better
shape.  That is why I'm arguing for XML Schema---to pick one of the
contenders, and the one that, I think, has the closest relationship to
RDF/XML syntax.

[...]

Peter F. Patel-Schneider
Received on Wednesday, 5 December 2001 09:11:18 GMT

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