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Re: S&AS comments

From: Jeff Z. Pan <pan@cs.man.ac.uk>
Date: Mon, 23 Jun 2003 10:39:05 +0100
Message-ID: <006101c3396b$49ab68c0$6401a8c0@percival>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: <public-webont-comments@w3.org>

Peter,

Thanks for your reply to the last call comments. This email contains
comments to your reply and the online editor's draft of the S&AS document
[1].

In section 2.1 of [1],

> The other built-in OWL Schema datatypes are problematic for OWL, as
                              ^^^^^
discussed in the RDF Semantics [RDF MT].

Do you mean the other built-in "XML" schema (instead of OWL schema)
datatypes? And it is not clear to me where in RDF MT can I locate the
discussion about why the datatypes are problematic. It might be easier for
the readers to follow if some more details (e.g. section number in the RDF
MT document) are provided.

> Because there is no standard way to go from a URI reference to an
> XML Schema datatype in an XML Schema, there is no standard way to
> use user-defined XML Schema in OWL.

I am not sure about this. Usually a URI reference of this form
http://any.domainname/anyxsdfile.xsd#sss will be understood to denote a
user-defined XML Schema datatype named sss.  Even though it is not a
standard way in XML Schema, there is no harm adding that in OWL (implicitly
require that the datatype sss be derived from one of the built-in OWL
datatypes). Or do we want to support more datatypes than XML Schema
datatypes, so we don't like the file extension xsd?

> Sections 2 and 3 have been modified to make rdf:XMLLiteral a built-in OWL
> datatype and rdfs:Literal not a built-in OWL datatype.  Data ranges now
> include rdfs:Literal as a special case.  VD is then the built-in OWL
> datatypes plus rdfs:Literal.  This has no real effect on the semantics.
> You can see the revised document at
> http://www-db.research.bell-labs.com/user/pfps/owl/

Yep, it is clearer now.

> > (3) In the definition of datatype theory, it is not clear that what
kinds
> > of datatypes can be in the set D. Does it contain only the built-in OWL
> > datatypes, or also their derived datatypes? If it can only consist of
> > built-in OWL datatypes, the datatype theory is quite limited and seems
to
> > me not enough in many cases.
>
> Datatype theories could include more than the built-in datatypes.
However,
> there would have to be a private understanding as to the meaning of these
> datatypes, as OWL has no mechanisms for providing such meaning.

It is good to have more than the built-in datatypes. However, it is not
clear to me how this "private understand" approach works.

[1] http://www-db.research.bell-labs.com/user/pfps/owl/semantics/

Regards,
Jeff
--
Jeff Z. Pan  ( http://DL-Web.man.ac.uk/ )
Computer Science Dept., The University of Manchester
Received on Monday, 23 June 2003 05:29:31 GMT

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