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Re: OWL datatype questions, with references

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Mon, 10 Feb 2003 07:16:21 -0500 (EST)
Message-Id: <20030210.071621.91550339.pfps@research.bell-labs.com>
To: lobrst@mitre.org
Cc: www-webont-wg@w3.org

From: Leo Obrst <lobrst@mitre.org>
Subject: OWL datatype questions, with references
Date: Sun, 09 Feb 2003 18:28:44 -0500

> Folks, 
> I am relaying these questions from a prospective user and close reader
> concerning inconsistencies or confusions on how OWL uses datatypes. I
> looked at the documents and couldn't answer definitively. Raphael raised
> some issues in datatype inconsistencies last week, but I don't know that
> these questions have been resolved. 
> The primary issue here seems to be: will OWL allow user-defined
> datatypes (not just those predefined by XML Schema)? 

Right now, no.  It would be nice, but 1/ apparently there is no way to refer
to datatypes in XML Schema documents and 2/ there is no way in RDF to use
datatypes other than the ones named in the RDF documents.

> Is OWL and the
> statements in RDF-CONCEPTS correlated, i.e., consistent? 

This should be the case.

> I point to the references below.
> Do we have a clear answer on this?
> Thanks,
> Leo
> -------- Original Message --------
> Subject: OWL datatype questions references
> Date: Thu, 06 Feb 2003 08:58:26 -0500
> From: amy kazura <alk@mitre.org>
> Organization: The MITRE Corporation
> To: "Obrst,Leo J." <lobrst@mitre.org>
> Leo -
> per our conversation yesterday, below are the references that i found
> unclear on
> exactly what datatypes are allowed in OWL.
> the statements in RDF-CONCEPTS lead me to believe that while it is
> expected that
> the majority of datatypes used will be the ones pre-defined by XML
> Schema, that
> it is certainly possible to define one's own, so long as the datatype
> URI is a
> URIref and the defining authority defines the value space, mapping, etc.

Actually, although it is possible to introduce datatypes to RDF, there is
no way of using them, because there is no way in RDF to provide a URI
reference for the datatype.  The only exception is the built-in datatype
XMLLiteral and the built-in XML Schema datatypes, which are explicitly
given URI references.

> a few of the statements regarding datatypes in the OWL docs also give
> this
> impression (e.g., ABSTRACT-SYNTAX 4.2 and GUIDE 3.2.2), but others seem
> to imply
> that the only datatypes allowed are those defined in the xsd namespace
> (http://www.w3.org/2001/XMLSchema#).

This is correct.

> if i mentally substitute the phrase "datatype defined in accordance with
> XMLSCHEMA2" each time i see "XML Schema datatype", then the OWL docs
> seem to
> mean what RDF-CONCEPTS does;  is this the intended interpretation ? 

No, OWL cannot use datatypes defined in XML Schema documents because such
datatypes do not have URI references.

> have i just
> been reading these incorrectly ?

We did think that it was possible to provide URI references for
user-defined XML Schema datatypes, so some of the wording in the OWL
documents may have been written with that in mind.


Received on Monday, 10 February 2003 07:17:05 UTC

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