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RE: Cutting the Patrician datatype knot

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Thu, 29 Nov 2001 08:37:42 -0500
To: Patrick.Stickler@nokia.com
Cc: www-rdf-interest@w3.org
Message-Id: <20011129083742M.pfps@research.bell-labs.com>
From: Patrick.Stickler@nokia.com
Subject: RE: Cutting the Patrician datatype knot
Date: Thu, 29 Nov 2001 13:27:57 +0200

> > > I don't read the charter as saying that RDF must use XML Schema
> > > data type *definition mechanisms*. Only that it should make best
> > > use of XML Schema defined data types. Those are not quite the
> > > same thing. 
> > 
> > Maybe not, but what would be the rationale for not using it?  
> > You gets lots
> > of benefits, including the ability to use existing XML Schema 
> > software.
> 
> But you can use XML Schema software with the P/DAML idioms
> as well. 

Sure, but, again, why invent new mechanisms when there already are existing
ones for the purpose?  Particularly as this is supposed to be a standards
effort, and the existing mechanisms are standards from the same
organization?  I really don't understand this seeming aversion to using the
results of other W3C working groups in the RDF Core working group.

> You don't, of course, expect the XML Schema parser
> to be interpreting typed data literals in the RDF serialization,
> right? 

No, I expect that the only way of typing literals, i.e., providing a
lexical-to-value map via syntactic means, would be via XML Schema
mechanisms.  I further expect that it should be possible to get *all* this
by passing RDF/XML through an XML parser and an XML Schema validator.

> So no matter what, some application has to provide
> an interface between the XML Schema validator/parser and
> the RDF graph, and the key information that is needed is the
> lexical form and the URI of the data type. The interface
> can then provide a meaningful serialization such as
> 
>    <some:datatype>lexical form</some:datatype>
> 
> to the XML Schema parser/validator and let it "do its thing"
> according to some XML Schema.

I don't think that this is necessary, except, perhaps, for literals (text
nodes) that do not get types from syntactically-local mechanisms.

> The important thing is that this pairing is clearly and
> consistently represented in the RDF graph so that it can
> be provided to all applications that need it, even XML
> Schema applications ;-)

I don't see this at all.  There are *lots* of other ways to represent typed
literals in an RDF graph.  Requiring in advance that an RDF graph represent
literals as pairs consisting of a datatype and a lexical form may eliminate
the best solution to typed literals in RDF.

> Cheers,
> 
> Patrick

Peter F. Patel-Schneider
Bell Labs Research
Received on Thursday, 29 November 2001 08:39:15 GMT

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