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Re: proposal to close Issue 5.8 Datatypes

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Mon, 25 Nov 2002 17:22:33 -0500 (EST)
Message-Id: <20021125.172233.68531521.pfps@research.bell-labs.com>
To: connolly@w3.org
Cc: www-webont-wg@w3.org

From: Dan Connolly <connolly@w3.org>
Subject: Re: proposal to close Issue 5.8 Datatypes
Date: 25 Nov 2002 15:57:23 -0600

> On Thu, 2002-11-21 at 19:12, Peter F. Patel-Schneider wrote:
> > 
> > I propose that we close issue 5.8 with the following resolution(s):
> > 
> > 1/ The exchange syntax for OWL will use RDF datatyping.
> 
> I'm not sure what it means to agree to that.
> 
> I suppose that "RDF datatyping" refers to something like
> http://www.w3.org/TR/2002/WD-rdf-syntax-grammar-20021108/#section-Syntax-datatyped-literals

... and the section of the RDF MT WD on datatyping

> but I'm not sure how this would show up in our
> ref/guide/semantics specs.

Well, I'm not sure how this would show up in our guide document as well.
My editor's draft of the semantics already has the appropriate wording.
The reference document would also have to change in some way.

> > 2/ The abstract syntax for OWL will use <datatype><lexical> as the syntax
> >    for typed data values and will only allow lexical forms that are valid
> >    for the datatype, i.e., <xd:integer>1.5 is not a valid typed literal in
> >    the abstract syntax.
> 
> It seems more clear to refer to the abstract syntax
> as being for OWL DL, since it's not a syntax
> for all of OWL.
> 
> > 3/ OWL will include all XML Schema built-in non-list simple types, using the
> >    canonical URI reference for them.
> 
> I'm not sure what it means for OWL to include a type.
> And I'm not sure why this is in the list in
> addtion to 1/.

The formal definition of RDF datatyping, in the RDF MT WD, does not require
any particular datatyping.  I'm proposing that OWL *does* include XML
Schema built-in non-list simple types.

> > 4/ OWL can use XML Schema non-list simple types defined at the top
> >    level of an XML Schema document and given a name, by using the URI
> >    reference constructed from the URI of the document and the local name of
> >    the simple type.  That is, if U is the URI of an XML Schema document
> >    that contains, 
> >    <xsd:schema ...>
> >      <xsd:simpleType name="foo">
> >        <xsd:restriction base="integer">
> >         <xsd:minInclusive value="1700">
> >        </xsd:restriction>
> >      </xsd:simpleType>
> >      ...
> >    </xsd:schema>
> >    then the URI reference U#foo will be that datatype.
> 
> Hmm... it doesn't seem reasonable for our spec to say what
> somebody else's URIref means. I'm not sure how to state
> my objection clearly, since of course we can use OWL
> to express constraints on the meaning of somebody
> else's URIs...
> 
> But the form of specification you used doesn't work...
> "if U is the URI of an XML schema document" is
> an ill-formed definite description; there isn't
> a well-defined mapping from XML Schema documents
> to URIs.

Huh?  Are not XML Schema documents WWW documents?  Do not all WWW documents
have URIs?

> >    Implementations of OWL may choose to ignore the facets such a type.
> 
> I don't know what it means to agree to that either.

This is simply an acknowledgment that user-defined XML Schema simple types
may be too complicated for any current reasoner to handle.  

> > 5/ Cardinality restrictions in the exchange syntax for OWL will use typed
> >    literals, as in 
> >              _:x rdf:type owl:Restriction .
> >              _:x owl:onProperty ex:foo .
> >              _:x owl:cardinality "5"^^xsd:decimal . 
> > 
> > The semantics document has been updated to reflect all this,
> 
> If you could refer me to specific text, I'd appreciate it.

Looking for ``datatype'' (case insensitive) should do the trick.

> > but some
> > changes probably need to be made to the other documents.
> 
> -- 
> Dan Connolly, W3C http://www.w3.org/People/Connolly/

peter
Received on Monday, 25 November 2002 17:22:43 GMT

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