W3C home > Mailing lists > Public > www-webont-wg@w3.org > May 2002

Re: LANG: number range expressions

From: David Trastour <david_trastour@hp.com>
Date: Thu, 2 May 2002 21:11:53 +0100
Message-ID: <008201c1f215$9b7d7510$0a1a7c0f@trastourd4>
To: "Dan Connolly" <connolly@w3.org>, "Ziv Hellman" <ziv@unicorn.com>
Cc: <www-webont-wg@w3.org>
I agree with Ziv and Dan that OWL needs some constraint mechanism for
datatype properties.
And XML Schema facets could be a solution to this problem.

> But the group decided to keep the datatypes and the rest of the universe
> of discourse separate, and this was one of the related consequences.

I think what has been decided is to keep classes and datatypes disjoint, as
well as object properties
and datatype properties. Now this may be a naive question but could we find
a syntactic solution
to express datatype constraints in an OWL document? Having classes and
datatypes disjoint does
not mean that they cannot coexist in the same document. As shown by Dan's
example, an RDFified
version of XML Schema facets would be much more usable than we currently
have in DAML+OIL.

I would like to bring another point concerning datatypes. As far as I know
DAML+OIL only supports
unary datatype constraints. I would be curious to hear people's opinion
about OWL supporting
n-ary datatype constraints. We could then make a level1/level2 distinction:
o level 1 does not support datatype constraints or only supports unary
constraints.
o level 2 supports n-ary datatype constraints.

Cheers,
David
----- Original Message -----
From: "Dan Connolly" <connolly@w3.org>
To: "Ziv Hellman" <ziv@unicorn.com>
Cc: <www-webont-wg@w3.org>
Sent: Thursday, May 02, 2002 7:53 PM
Subject: Re: LANG: number range expressions


> On Thu, 2002-05-02 at 12:46, Ziv Hellman wrote:
> > I was recently looking through some DAML+OIL documentation and I noticed
> > that in order to, for example, constrain the property 'age' of a class
> > Adult to being 17 or over, one needs the following syntax.
> >
> > <daml:Class rdf:ID="Adult">
> >  <daml:intersectionOf rdf:parseType="daml:collection">
> >  <daml:Class rdf:about="#Person"/>
> >     <daml:Restriction>
> >       <daml:onProperty rdf:resource="#age"/>
> >       <daml:hasClass
> >
> > rdf:resource="http://www.daml.org/2001/03/daml+oil-ex-dt#over17"/>
> >     </daml:Restriction>
> >   </daml:intersectionOf>
> > </daml:Class>
> >
> > <xsd:simpleType name="over17">
> >   <!-- over17 is an XMLS datatype based on decimal -->
> >   <!-- with the added restriction that values must be >= 17 -->
> >   <xsd:restriction base="xsd:decimal">
> >   <xsd:minInclusive value="17"/>
> >   </xsd:restriction>
> > </xsd:simpleType>
>
> In the course of the design of DAML+OIL, I suggested incorporating
> XML Schema datatype facets into RDF/DAML+OIL; it might look
> like this...
>
> <rdf:RDF
>     xmlns:dt="http://www.w3.org/2001/XMLSchema#"
>     xmlns:ex="http://example/vocab#"
>     xmlns:ont="http://www.daml.org/2001/03/daml+oil#"
>     xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
>     xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#">
>
>     <rdfs:Class rdf:about="http://example/vocab#Adult">
>         <ont:intersectionOf rdf:parseType="ont:collection">
>           <rdfs:Class rdf:about="http://example/vocab#Person"/>
>           <ont:Restriction>
>             <ont:hasClass rdf:parseType="Resource">
>               <ont:intersectionOf rdf:parseType="ont:collection">
>                 <rdfs:Class
> rdf:resource="http://www.w3.org/2001/XMLSchema#decimal"/>
>                 <rdfs:Class>
>                   <dt:minInclusive>17</dt:minInclusive>
>                 </rdfs:Class>
>               </ont:intersectionOf>
>             </ont:hasClass>
>             <ont:onProperty rdf:resource="http://example/vocab#age"/>
>           </ont:Restriction>
>         </ont:intersectionOf>
>     </rdfs:Class>
> </rdf:RDF>
>
> or something like that.
>
> But the group decided to keep the datatypes and the rest of the universe
> of discourse separate, and this was one of the related consequences.
>
> I have raised the issue of splitting datatypes out...
>
http://www.w3.org/2001/sw/WebOnt/webont-issues.html#5.1-Uniform-treatment-of
-literal/data-values
>
> But maybe this is worth a separate issue.
>
> In the RDF Core WG's discussions about datatypes, I recently
> suggested we include facets in the design...
>
>   # user-defined datatype (facet) support needed?
>   Dan Connolly (Tue, Apr 30 2002)
>   http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2002Apr/0547.html
>
>
>
> [...]
> > Will OWL inherit this type of behaviout from DAML+OIL?
>
> Unless somebody raises an issue and we decide to resolve
> the issue by changing it, yes.
>
> --
> Dan Connolly, W3C http://www.w3.org/People/Connolly/
>
>
Received on Thursday, 2 May 2002 16:13:21 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:57:49 GMT