Comment: issues with owl time

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Comment: issues with owl time

Antoni Mylka

Many applications use the TZ timezone database
(http://www.twinsun.com/tz/tz-link.htm). Is there a mapping between TZ
timezones and the timezones from the www.w3.org/2006/timezone-world or
www.w3.org/2006/timezone-us?

The DurationDescription class doesn't support negative durations
(as the XSD duration datatype does). Such negatve durations come up in
iCal files. (That's why using a DurationDescription to represent an ical
Duration would need some additional information if it's negative)

The timeZoneProperty of the owl-time ontology points to a timezone, not
to a Region. Doesn't it imply loss of information? It would be nice to
be able to attach a DateTimeDescription to a geographical region.

Antoni Mylka
[hidden email]


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Re: Comment: issues with owl time

Feng Pan

Hi Antoni,

Thank you for your comments.

> Many applications use the TZ timezone database
> (http://www.twinsun.com/tz/tz-link.htm). Is there a mapping between TZ
> timezones and the timezones from the www.w3.org/2006/timezone-world or
> www.w3.org/2006/timezone-us?

No, currenly there is no mapping between them, but it would be useful
to explore that.

> The DurationDescription class doesn't support negative durations
> (as the XSD duration datatype does). Such negatve durations come up in iCal
> files. (That's why using a DurationDescription to represent an ical Duration
> would need some additional information if it's negative)

Thank you for pointing that out. I think the negative durations are only
used for subtractions in temporal arithmetic. For those cases, subtraction
rules can be applied to the positive durations.

> The timeZoneProperty of the owl-time ontology points to a timezone, not
> to a Region. Doesn't it imply loss of information? It would be nice to be
> able to attach a DateTimeDescription to a geographical region.

It seems when we use time zones for dateTimes, we are most interested in
which time zone it is in and how much time offset from GMT/UTC. For
example, XSD:dateTime only has the duration offset from UTC for time
zones.

Thanks,

Feng

--
Feng Pan, Ph.D. Candidate
USC Information Sciences Institute (ISI)
Email: [hidden email]
Web: http://www.isi.edu/~pan/

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Re: Comment: issues with owl time

Pat Hayes

>Hi Antoni,
>
>Thank you for your comments.
>
>>Many applications use the TZ timezone database
>>(http://www.twinsun.com/tz/tz-link.htm). Is there a mapping between TZ
>>timezones and the timezones from the www.w3.org/2006/timezone-world or
>>www.w3.org/2006/timezone-us?
>
>No, currenly there is no mapping between them, but it would be useful
>to explore that.
>
>>The DurationDescription class doesn't support negative durations
>>(as the XSD duration datatype does). Such negatve durations come up in iCal
>>files. (That's why using a DurationDescription to represent an ical Duration
>>would need some additional information if it's negative)
>
>Thank you for pointing that out. I think the negative durations are
>only used for subtractions in temporal arithmetic. For those cases,
>subtraction rules can be applied to the positive durations.

They do have other, more 'ontological' uses. For example, if one is
reasoning about the interval by which one event precedes another -
defined as the interval <start(event1), start(event2)> - it can be
useful to allow a negative interval to represent the fact that event2
started earlier than event1. In general, negative intervals provide
an analogous utility in temporal reasoning to that which negative
numbers provide in arithmetic, in effect by making the algebra more
complete and so providing more solutions to temporal constraints.
They mean for example, that any two timepoints P and Q define an
interval <P, Q>. Just as with negative numbers, however, the cost is
that the algebra is more complicated: the Allen interval algebra
applies only to positive intervals.

Pat Hayes
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