|To:||"[ontolog-forum] " <ontolog-forum@xxxxxxxxxxxxxxxx>|
|From:||Pat Hayes <phayes@xxxxxxx>|
|Date:||Mon, 21 Jan 2008 10:18:26 -0600|
At 9:37 AM -0500 1/21/08, John F. Sowa wrote:
There are a lot of ontologies for time, in various notations, all pretty similar except of course for the all-important details. I wrote a survey of some of the many options some time ago (all written in KIF), which is available here
and since then a fairly 'standard' ontology was put together for the W3C OWL-based SWServices project by Jerry Hobbs and Feng Pan, originally written in a conventional FOL notation and then as far as possible transcribed into OWL.
There is a lot of commentary, advice, etc.., about this, see for example http://www.geospatialsemanticweb.com/2006/09/29/tips-on-using-the-w3c-owl-time-ontology
and it contains a lot of new stuff, eg a complete ontology of international time-zones and so on. It is probably the most thoroughly worked out 'practical' time ontology.
BTW, if you see a reference to DAML-Time, it was the early version of this, now obsoleted.
The XMLSchema datatype scheme has a fairly complex temporal naming system worked out for dates and times, but it gets rather tangled when it tries to merge months and days.
As I use it, the first argument of PTim is some physical event
specified as true points, there is always an implicit granularity.
Pity you called them 'points', then, as they are in fact intervals :-) How do you handle endpoints of intervals: are they intervals also? One problem with this approach is that the Allen relationships change when you change granularity levels, which wrecks some reasoners.
Therefore, the second argument could be any of the following,
Cute. The OWL-Time used a similar device, borrowed I believe from the CYC temporal ontology, in which each successive layer of granularity is treated as a 'selection' function on the previous level, so that 21 January 2008 has the structure 'the 21st day of( the first month of( the 2008th year of(The Christian Calender)))'. This makes both temporal and logical sense.
Do you have any granularity axioms? That is one of the hardest ontological problems, in my experience.
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