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Re: Dataypes, literals, syntax

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Fri, 19 Jul 2002 09:21:30 -0400
To: jonathan@openhealth.org
Cc: www-rdf-logic@w3.org
Message-Id: <20020719092130G.pfps@research.bell-labs.com>

From: "Jonathan Borden" <jonathan@openhealth.org>
Subject: Dataypes, literals, syntax
Date: Fri, 19 Jul 2002 08:56:02 -0400

> 
> I just noticed:
> http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2002Jul/0121.html
> 
> It got me thinking about literal datatypes (the above considers XML
> datatypes).
> 
> Why not:
> 
> <rdf:Description rdf:about="foo://bar">
>     <ex:property xsi:type="xsd:integer">10</ex:property>
> </rdf:Description>
> 
> being defined to parse to:
> 
> <foo://bar> ex:property xsd:integer"10" .
> 
> wouldn't this solve much of the datatypes debate -- it would _syntactically_
> distinguish typed literals, as Drew McDermott correctly points out is the
> way to go, and would avoid issues related to nonmonotonicity related to
> interpreting a triple based on a schema that may or may not be present.

This has been proposed several times, by several people, including myself,
most recently in
  http://lists.w3.org/Archives/Public/www-rdf-comments/2002JulSep/0024.html
The RDF Core WG has, for some reason, chosen not to accept this in any
guise, even as part of a datatyping facility for RDF.

> Such a facility is compatible with XML Schema. This is how an XML Schema
> compatible application -- xsi: stands for XML Schema Instance -- would
> interpret explicit datatyping info for an XML document.

Yes.  It almost seems that XML compatability is considered a bad thing by
the RDF Core Working Group.

> Suppose that RDF were defined 'on top of' the _post schema validation_
> infoset (PSVI) or alternately a _type adorned infoset_ (TAI), rather than
> the plain XML infoset. In that case, datatypes would be explicitly provided
> to RDF applications.

Good idea.  See
   http://www-db.research.bell-labs.com/user/pfps/papers/yin-yang.pdf 
and
   http://www-db.research.bell-labs.com/user/pfps/papers/building.ps 
for an even more radical proposal along these lines.

> Otherwise RDF is not really using XML Schema _datatypes_ which really means
> that the PSVI/TAI is being used as the input for an application that defines
> semantics, rather in the absense of the PSVI/TAI -- i.e. the current
> situation -- RDF is merely trying to use the XML Schema _datatype qnames_
> which for which I don't see a clear consensus on how to proceed.

There are lots of difficult issues in integrating XML Schema and RDF,
partly due to different non-technical pressures on the solution, and the
RDF Core Working Group has been wrestling with them for quite some time
now.  If all that can be done is using named XML Schema datatypes, but this
is done well, then I think significant progress will have been made.  I am
not optimistic that even this can be done.

> Jonathan

peter
Received on Friday, 19 July 2002 09:21:39 GMT

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