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Re: proposal for dateTime (ISSUE-138)

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 15 Oct 2008 12:44:42 -0400 (EDT)
Message-Id: <20081015.124442.93868486.pfps@research.bell-labs.com>
To: msmith@clarkparsia.com
Cc: public-owl-wg@w3.org

From: "Mike Smith" <msmith@clarkparsia.com>
Subject: Re: proposal for dateTime (ISSUE-138)
Date: Wed, 15 Oct 2008 12:32:23 -0400

> On Mon, Oct 13, 2008 at 12:37, Peter F. Patel-Schneider
> <pfps@research.bell-labs.com> wrote:
> 
> > There has been some discussion of whether OWL can use XSD's new datatype
> > dateTime with required timezone, because our notion of equality derives
> > from the timeline for time, not the XSD 7-value internal data structure
> > for xsd:dateTime.  However, our notion of equality *is* the notion of
> > equality used in XSD for dateTime values with a required timezone, and
> > thus retains compatibility with XSD.
> 
> Has the XML schema group changed the semantics such that identity and
> equality are the same?

Precisely not, and this is why we would be OK.

> The test case at [1] is consistent because with owl:dateTime, equality
> and identity are the same.  If we were to adopt the timezone dependent
> notion of identity, the ontology in the test case would be
> inconsistent.

In OWL equality is semantic identity.  In XSD 1 equality was determined
from data structure identity.  In XSD 1.1 equality can differ from data
structure identity.

Consider float.  In XML 1 -0 and +0 were not data-structure identical,
and were thus unequal.  In XML 1.1 -0 and +0 are still not
data-structure identical, but are equal.  

> -- 
> Mike Smith
> 
> Clark & Parsia
> 
> [1] http://www.w3.org/2007/OWL/wiki/TestCase:Datatype-DateTime-001

peter
Received on Wednesday, 15 October 2008 16:58:55 GMT

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