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Re: Order relation on time (Schema comments, 14 Aug 03)

From: Dave Peterson <davep@iit.edu>
Date: Fri, 9 Dec 2005 11:34:48 -0500
Message-Id: <a06230900bfbf6240ca1b@[192.168.0.9]>
To: Schema Comments <www-xml-schema-comments@w3.org>

[N.B.:  This msg was sent to steve.hanna@sun.com on 28 Oct 2005 -DP]

Steve:  I've just had occasion to review your comment; let me point out
the following.

You wrote:

>However, the algorithm I described for calculating answer 2
>above is not easily inferred from the specification. The
>specification says "The order relation on time values is the
>Order relation on dateTime (section 3.2.7.3) using an
>arbitrary date." We believe that this means that for time
>values with time zones, you must normalize the dates into a
>single 24 hour period before applying the Order relation on
>dateTime. An easy way to do this is to normalize the time
>values to UTC and then assign an arbitrary year-month-day
>value to them. But a more natural interpretation of the spec
>would be to skip the normalization step and just assign the
>year-month-day value. This will probably work just fine until
>you encounter a situation like the one given above. We ran into
>this while working on an XACML implementation (which uses the
>XML Schema ordering for time values).

Your "Answer 1" was obviously correct, and it *is* obvious if
you realize that the *values* 2002-02-16T09:00:00+12:00 and
2002-02-16T09:00:00-12:00 are identical.  The two lexical
representations '2002-02-16T09:00:00+12:00' and
'2002-02-16T09:00:00+12:00' map to the same value.  The
possible confusion comes from forgetting that lexical
representations are not values.

Since the only question was whether Answer 1 was sufficiently
obvious (you give the argument why it's correct in your own
msg), I don't expect the Schema WG will make any official
response.  It came up in the WG as they were going through
a list of all not-known-to-be-closed issues.

FYI, in Schema 1.1, now in preparation, things are being changed
to more closely align with QT.  date/time values will "know"
their timezones.

I suppose if nothing ever changed, guys like us would be working
for minimum wage....  ;-)
--
Dave Peterson
SGMLWorks!

davep@iit.edu
-- 
Dave Peterson
SGMLWorks!

davep@iit.edu
Received on Friday, 9 December 2005 16:39:48 GMT

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