At 4:47 PM +0000 1/22/08, Ian Bailey wrote:
>Hi Pat,
>
>In a 4D Ontology, what you refer to as a point in time is actually an extent
>with one dimension (time) tending towards zero and the other three tending
>towards infinity. (01)
Hi. I'm familiar with the 4-d approach, and like
it: but the 4-d vs. continuant debate is a tarpit
of endless debate which we can avoid while
sticking closely to the topic of time. (02)
When discussing 4-d, time is indeed a dimension,
so the intervals/points discussion is about the
structure of that particular coordinate. (03)
>More usually, one is interested in a "point in time" over
>a finite 3D extent though (ignoring relativistic considerations, which in
>most earth-bound situations we can (04)
Yes, lets please ignore relativity. Never mind
earth-bound: the Voyager probe got all the way to
the Kuiper belt using Newtonian physics. (05)
>). We can talk about 4:00 UST all over the
>world. That is not a point, it's an extent in four dimensions. (06)
4:00 all over the world is a 3-d extent in 4
dimensions, forming the temporal boundary of a
4-d entity which we might call 3:00-to-4:00 all
over the world. However, 4pm is indeed a point on
the time axis, the projection of 4:00 all over
the world onto that axis. (07)
>I'm sure Chris Partridge or Matthew West can explain this more precisely
>than me, so apologies if my terminology is not quite correct.
>
>>From a purely pragmatic point of view (I'm what Chris describes as a
>"hairy-arsed engineer"), 4D works and works very well - we've been working
>with for years in ISO15926, and we chose the same approach for the IDEAS
>Ontology (www.ideasgroup.org) 'cos it works. I've seen far too many bodged
>and inconsistent attempts to manage time in data models and ontologies over
>the years. The 4D approach gives you a pattern for representing change over
>time that works in all cases and works consistently. (08)
I agree wholeheartedly. One of the worst
decisions in recent ontology engineering has been
the rejection of the 4-d approach in the medical
ontology standards such as BOF and DOLCE. Putting
these into a 4-d framework eliminates the useless
and confusing need to duplicate content in two
'styles', once for continuants (things) and the
other for occurrents (events). (09)
Pat (010)
>
>Cheers
>--
>Ian Bailey
>www.modelfutures.com
>T: +44 207 193 4605
>M: +44 7768 892362
>Skype
>
>Model Futures Limited is a company registered in England and Wales with
>company number 05248454
>Registered Company Address: 1 Nelson Street, Southend-On-Sea, Essex, SS1 1EG
>VAT Number: 848 7357 75
>
>
>But those start and end times ARE points. Really,
>you can't get away from it: if you have
>intervals, you have the points at their ends.
>They might not be points in the mathematical real
>line, but they are points in the following senses:
>
>1. they are indivisible (unless you change your interval topology)
>2. they are the places where intervals meet one another
>3. they are uniquely determined by your intervals
>4. they determine the time ordering on the intervals
>
>And this is independent of whether or not you have continuous or dense time.
>
>Pat
>
>
>>All this for me is independent of whether time is ultimately granular
>>or continuous. Ultimately this only means at what point we can not longer
>>tell whether one event happened before another.
>>
>>
>>Regards
>>
>>Matthew West
>>Reference Data Architecture and Standards Manager
>>Shell International Petroleum Company Limited
>>Registered in England and Wales
>>Registered number: 621148
>>Registered office: Shell Centre, London SE1 7NA, United Kingdom
>>
>>Tel: +44 20 7934 4490 Mobile: +44 7796 336538
>>Email: matthew.west@xxxxxxxxx
>>http://www.shell.com
>>http://www.matthew-west.org.uk/
>>
>>
>>> -----Original Message-----
>>> From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
>>> [mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx]On Behalf Of
>>> John F. Sowa
>>> Sent: 21 January 2008 17:48
>>> To: [ontolog-forum]
>>> Subject: Re: [ontolog-forum] Time representation
> >>
>>>
>>> Pat,
>>>
>>> The position I most strongly advocate is not a specific ontology,
>>> but a framework of conventions for organizing a multiplicity
>>> of special cases (not necessarily consistent with one another),
>>> making the implicit relationships explicit, and providing tools
>>> and guidelines for mixing and matching. The lattice of theories
>>> is an example. Robert Kent's IFF is a much more ambitious example.
>>>
>>> I would recommend a fairly simple framework for starters, since
>>> there's a danger of freezing half-baked ideas before they're fully
>>> baked. (RDF, for example, was hardly out of the oven before
>>> Tim Bray tried, unsuccessfully, to pull it back in.)
>>>
>>> > Do you have any granularity axioms? That is one of the hardest
>>> > ontological problems, in my experience.
>>>
>>> There are so many hard problems, it's hard to say which are harder.
>>> But the idea of taking the least significant digit as the criterion
>>> for implicit granularity is fairly common for experimental data
>>> (unless some explicit margin of error is stated).
>>>
>>> Re PTim: I realize that calling an interval a point is problematical.
>>> But in anything that has to do with the physical world, there is no
>>> way to specify a true point. Perhaps a better term would be "grain
>>> in time", abbreviated "Grit".
>>>
>>> John
>>>
>>> PS re HTML email formats: Your note of 11:18 was in a readable font
>>> for Thunderbird, but your note of 11:37 appeared in a tiny, tiny font.
>> > I had to increase the font size by two steps to make it the same as
>>> the previous note. But then the fonts for all other notes were too
>>> big, and I had to decrease the default by two steps.
>>>
>>> At least each of your notes was entirely in one font size. I've
>>> received some email in which each paragraph was in a progressively
>>> smaller font. That's why I hate HTML email.
>>>
>>>
>>> _________________________________________________________________
>>> Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/
>>> Subscribe/Config:
>>http://ontolog.cim3.net/mailman/listinfo/ontolog-forum/
>>Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx
>>Shared Files: http://ontolog.cim3.net/file/
>>Community Wiki: http://ontolog.cim3.net/wiki/
>>To Post: mailto:ontolog-forum@xxxxxxxxxxxxxxxx
>>
>>
>>
>>
>>_________________________________________________________________
>>Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/
>>Subscribe/Config: http://ontolog.cim3.net/mailman/listinfo/ontolog-forum/
>>Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx
>>Shared Files: http://ontolog.cim3.net/file/
>>Community Wiki: http://ontolog.cim3.net/wiki/
>>To Post: mailto:ontolog-forum@xxxxxxxxxxxxxxxx
>>
>
>
>--
>---------------------------------------------------------------------
>IHMC (850)434 8903 or (650)494 3973 home
>40 South Alcaniz St. (850)202 4416 office
>Pensacola (850)202 4440 fax
>FL 32502 (850)291 0667 cell
>phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes
>
>
>_________________________________________________________________
>Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/
>Subscribe/Config: http://ontolog.cim3.net/mailman/listinfo/ontolog-forum/
>Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx
>Shared Files: http://ontolog.cim3.net/file/
>Community Wiki: http://ontolog.cim3.net/wiki/
>To Post: mailto:ontolog-forum@xxxxxxxxxxxxxxxx
>
>
>
>_________________________________________________________________
>Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/
>Subscribe/Config: http://ontolog.cim3.net/mailman/listinfo/ontolog-forum/
>Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx
>Shared Files: http://ontolog.cim3.net/file/
>Community Wiki: http://ontolog.cim3.net/wiki/
>To Post: mailto:ontolog-forum@xxxxxxxxxxxxxxxx
> (011)
--
---------------------------------------------------------------------
IHMC (850)434 8903 or (650)494 3973 home
40 South Alcaniz St. (850)202 4416 office
Pensacola (850)202 4440 fax
FL 32502 (850)291 0667 cell
phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes (012)
_________________________________________________________________
Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/
Subscribe/Config: http://ontolog.cim3.net/mailman/listinfo/ontolog-forum/
Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx
Shared Files: http://ontolog.cim3.net/file/
Community Wiki: http://ontolog.cim3.net/wiki/
To Post: mailto:ontolog-forum@xxxxxxxxxxxxxxxx (013)
|