ISSUE-177: Appendix B, Time Zone Resource in OWL

Appendix B, Time Zone Resource in OWL

State:

CLOSED

Product:

Time ontology in OWL

Raised by:

Simon Cox

Opened on:

2017-04-12

Description:

From https://www.w3.org/XML/2007/qts-timeont-comments#id64653

3.14. Appendix B, Time Zone Resource in OWL

Time zones as legal entities are subject to change over time. The U.S. changed the dates it transitions to and from daylight savings time in 2007 (Energy Policy Act of 2005). DaylightSavingsPolicy does not seem to be able to represent this complexity.

3.15. Appendix B "Time Zone Resource in OWL" 1st paragraph:

We have developed a time zone resource [15] in OWL for not only the US but also the entire world, including three parts: the time zone ontology file [16], the US time zone instance file [17], and the world time zone instance file [18].

Including support for “the entire world” is a good thing. The resource seems, however, to lack support for parts of the world. The list is long, but this is what struck us off the cuff:

- solar time that was used (just ONE example) in Saudi Arabia until 1950.
- support for different calendars, many of which are not "aligned" with the "ISO" one. Note also that things like the start of the year has changed over time even in the same calendar. [This comment though is not time zone specific.]

3.16. Appendix B, subsection "Time Zone Ontology" 4th bullet:

observesDaylightSavingsTime: true if the region goes on daylight savings time, false otherwise.

This "boolean" is unfortunately time-dependent! Take the example of Sweden:

Daylight savings time was introduced on a trial basis in 1916, but following protests from the farmers it was not repeated the following year. It was re-introduced in 1980. The start and end date has also varied considerably with time, which does not seem to be expressable.

3.17. Using the time zone ontology (Appendix B)

It is not clear how one would use the time zone ontology given, "The expected input to the ontology is a location, e.g. a city, and the output will be its current time offset, say -6 hours, from the Greenwich Mean Time (GMT)." in genealogical research, where one would presumably want the timezone for an historical date (to calculate astrological charts?) For this to work you'd need also to specify a year -- e.g. there was a double DST in effect during WWII, and in most countries summer time was not used at all before WW I.

3.18. GMT Offset (Appendix B.1)

The offset “GMToffset: an XML Schema duration between -12 and +14 hours.” appears to be sufficient to hold any actual timezone in current use, although it's not clear whether it takes DST into account. But the range of actual time zones has changed somewhat in recent years, and there is little likelihood that such changes will cease in the foreseeable future.

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Related emails:

1. OWL-Time - ISSUE-177: Appendix B, Time Zone Resource in OWL (from Simon.Cox@csiro.au on 2017-04-12)

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