At 9:47 AM +0000 1/22/08, <matthew.west@xxxxxxxxx> wrote:
>Dear John,
>
>I'm glad you brought it up, because it was on my mind too:
>
>> 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".
>
>I think one of the constant challenges of ontology is to differentiate
>between common practice ways of representing things, e.g.
>
>> 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).
>
>And what they really are, i.e. in this case an interval or period. Now
>there is, in my mind, nothing wrong with naming an interval 14th Jan
>2008, but it needs to be understood that it has a start time of midnight
>at the start of the day, and an end time of midnight at the end of the
>day, and that it is not in any sense a point in time. (01)
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: (02)
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 (03)
And this is independent of whether or not you have continuous or dense time. (04)
Pat (05)
>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
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>
>Tel: +44 20 7934 4490 Mobile: +44 7796 336538
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>
>
>> -----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.
>>
>>
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