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OWL datatype questions, with references

From: Leo Obrst <lobrst@mitre.org>
Date: Sun, 09 Feb 2003 18:28:44 -0500
Message-ID: <3E46E42C.E317C284@mitre.org>
To: W3C Web Ontology WG <www-webont-wg@w3.org>


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

I point to the references below.

Do we have a clear answer on this?


-------- 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.

a few of the statements regarding datatypes in the OWL docs also give
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

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 ? 
have i just
been reading these incorrectly ?

also, i did not get a chance to write up my other questions last night; 
get those to you early next week.




2. Abstract Syntax
"OWL uses some of the facilities of XML Schema. [XML Schema Datatypes].
following built-in non-list XML Schema datatypes, called the OWL
datatypes, can
be used in OWL by means of the XML Schema canonical URI reference for
datatype, http://www.w3.org/2001/XMLSchema#name, where name is the local
name of
the datatype"

2.1. Ontologies
"If a URI reference is a datatype, i.e., the URI reference points to one
of the
useful XML Schema datatypes described above, then that URI reference
cannot be
used as the identifier of a class"

3.1. Vocabularies and Interpretations
"S is extended to typed data literals by utilizing the XML Schema
mapping for
the datatype, i.e., S(d l) is the value corresponding to l for the XML
dataytpe d. (P is the power set operator.)

Abstract OWL interpretations have the following conditions having to do
with OWL

If d is the canonical URI reference for an OWL datatype then EC(d) is
the XML
Schema value space for that datatype."

4.2. Definition of OWL DL and OWL Lite Ontologies in RDF Graph Form
"A node x in G is a datatype if x is a URI reference and there is a
triple of
the form x rdf:type rdfs:Datatype ."


Web Ontology Language (OWL) Reference Version 1.0
Editor's Draft document - no W3C status at this time
This version:
$Id: owl-ref-proposed.html,v 1.165 2003/02/04 05:31:01 mdean Exp $

7. Datatypes

"OWL allows two types of data range specifications:

An RDF datatype specification.
An enumerated datatype, using the owl:oneOf construct."

7.1 RDF Datatypes

"OWL makes use of the RDF datatyping scheme, which provides a mechanism
referring to XML Schema datatypes....
....A typed literal needs to have an RDF attribute rdf:datatype of which
value should be a URI reference to an XML Schema datatype.
The OWL Guide document [OWL Guide] contains a table of frequently-used
types. For a full listing, see the XML Schema documentation [XML Schema


3.2.1. Defining Properties
"datatype properties, relations between instances of classes and RDF
and XML Schema datatypes"

3.2.2. Properties and Datatypes
"Datatype properties may range over strings or they may make use of
simple types
defined in accordance with XML Schema datatypes."



2.2.5 Use XML Schema Datatypes
"RDF can use values represented according to XML schema datatypes

3.3 Datatypes
"RDF uses the datatype abstraction defined by XML Schema Part 2:
[XML-SCHEMA2], and may be used with any datatype definition that
conforms to
this abstraction, even if not actually defined in terms of XML Schema.
Rather, RDF defers to datatypes that are defined separately, and
identified with
URI references.
The defining authority of a URI which identifies a datatype is
responsible for
specifying the datatype's lexical space, value space and datatype

RDF provides no mechanism for defining new datatypes. XML Schema
[XML-SCHEMA2] provides an extensibility framework suitable for defining
datatypes for use in RDF."

6.5 RDF Literals
"The datatype URI being an RDF URI reference."
Received on Sunday, 9 February 2003 18:28:58 GMT

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