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Re: draft of LC comment to XML Schema WG

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Mon, 04 Aug 2008 09:58:51 -0400 (EDT)
Message-Id: <20080804.095851.47282026.pfps@research.bell-labs.com>
To: schneid@fzi.de
Cc: public-owl-wg@w3.org

From: "Michael Schneider" <schneid@fzi.de>
Subject: RE: draft of LC comment to XML Schema WG
Date: Mon, 4 Aug 2008 15:40:25 +0200

> Hi Peter!
> 
> Sounds like a pretty clear read to me. A few remarks/questions follow
> inline. 
> 
> Peter F. Patel-Schneider wrote:
> 
> >Here is my proposed LC comment to the XML Schema WG concerning datetime.
> 
> [snip]
> 
> >For the purposes of reasoning in OWL, it is much easier to deal with
> >dateTime values where the timezone is present.  Such values can be
> >converted to single time points (using timeOnTimeline) 
> 
> What is 'timeOnTimeline'? Is this something that XSD people know? 

They should.  It is how dateTime values are compared.

> >and a complete
> >order determined from the time points.  We would thus like to have a
> >derived XML Schema datatype for dateTime with a required timezone.  [I
> >added this last sentence based on some evidence but the WG should
> >confirm.]
> 
> How is the XSD group supposed to understand "derived XML Schema datatype"?
> As a datatype different from the original xsd:dateTime?

Derived datatype is a technical term in the XML Schema datatype
specificaiton.

> [snip]
> 
> >This treatment of dateTime values appears to violate the document, as
> >different dateTime values that compare equal according to the document
> >are turned into dateTime values that do not compare equal. 
> 
> I am not clear whether I correctly understand this sentence. Does this refer
> to the situation that a non-timezoned dateTime is compared to a dateTime
> with a timezone? Because the comparison between two dateTimes without a
> timezone should always lead to the same result for both XSD and OWL, or do I
> overlook something here?

Yes.  If a tool "repairs" dateTime values without a timezone by putting
in a local timezone, then two dateTime values that are identical
according to XML Schema datatypes may end up being unequal (because they
receive different timezone values).

> Cheers,
> Michael

peter
Received on Monday, 4 August 2008 14:09:52 GMT

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