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Re: Datatype disjointness implemented

From: Alan Ruttenberg <alanruttenberg@gmail.com>
Date: Thu, 12 Mar 2009 15:55:53 -0400
Message-ID: <29af5e2d0903121255m68be9084oa64d27df5a8752ad@mail.gmail.com>
To: Boris Motik <boris.motik@comlab.ox.ac.uk>
Cc: W3C OWL Working Group <public-owl-wg@w3.org>
The change includes:

xsd:double
xsd:float
Value Spaces. The value spaces of xsd:double and xsd:float are
specified in XML Schema Datatypes [XML Schema Datatypes]. Furthermore,
the value spaces of owl:real, xsd:double, and xsd:float are pairwise
disjoint.

This is inconsistent, as it is inconsistent in XML Schema. The value
spaces of both decimal and float and doubles are all "numbers" in XML
Schema, notwithstanding their later protestation that the sets are
disjoint. Specifically, it says, for floats:

"Its value space is a subset of the rational numbers."

This is inconsistent with floats being disjoint with owl:real, which
has as a subset, owl:rational.

We can't repeat this inconsistency in OWL. If the value spaces are to
be disjoint, it needs to be explicitly stated how this comes about.
However I see no such theory other than the informal:

"Thus, the value spaces of xsd:double and xsd:float can be understood
as containing "fresh copies" of the appropriate subsets of the value
space of owl:real."

An appropriate way to do this would be to have the value spaces of OWL
numbers not be numbers, but instead be pairs of numbers and tag. I
interpret this to mean that we are *not* adopting the value spaces as
specified by XML Schema, somewhat nullifying the motivation for the
change.

Note that I do not, in pointing this out, consider such a repair as
removing our overruled objection to the overall change. However, if
the change is to be adopted, it needs to done in a careful and
consistent manner.

-Alan

Speaking as representative of Science Commons



On Thu, Mar 12, 2009 at 7:44 AM, Boris Motik
<boris.motik@comlab.ox.ac.uk> wrote:
> Hello,
>
> I've just implemented yesterday's decision about datatype disjointness.
>
> The changes in the Syntax document are localized to Section 4. Here is the diff,
> although I doubt that it will be of great use, since the changes were many:
> http://www.w3.org/2007/OWL/wiki/index.php?title=Syntax&diff=19585&oldid=19563
>
> Profiles:
> http://www.w3.org/2007/OWL/wiki/index.php?title=Profiles&diff=19586&oldid=19552
> The change here was to remove the reference to owl:realPlus. Also, as far as I
> remember from the F2F, we said that we'd include xsd:float and xsd:double into
> OWL 2 RL after deciding on the disjointness, so this is what I did.
>
> Regards,
>
>        Boris
>
>
>
Received on Thursday, 12 March 2009 19:56:29 GMT

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