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Re: [ontolog-forum] Time representation

To: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: "John F. Sowa" <sowa@xxxxxxxxxxx>
Date: Mon, 21 Jan 2008 13:43:35 -0500
Message-id: <4794E7D7.8080907@xxxxxxxxxxx>
Pat,    (01)

Your note of 12:15 is now in the same size as the note of 11:18.    (02)

JFS>> An approach with explicit time represents time with a linear
 >> coordinate system.    (03)

PH> Why linear? There are branching-time ontologies, circular-time
 > ontologies, etc.. And it need not be a coordinate system exactly:
 > many temporal ontologies have no metric information in them at all.    (04)

I agree.  Sandewall's examples, which I cited, include those.
When I contrasted explicit time with temporal logics, I just
happened to be thinking of the default model.    (05)

JFS>> But finite intervals with domain-dependent granularity
 >> are more realistic.    (06)

PH> But such intervals tend to have points at their ends, and meet
 > at points. Its usually most useful to have both kinds of entity,
 > or if you must restrict to one, use points and treat an interval
 > as a pair of (end)points.    (07)

You could also consider a grain to be specified by a probability
distribution of measurements whose median, mean, or mode is the
designated point.  Or variations of fuzzy or rough methods.    (08)

PH> And there are other options in more expressive notations,
 > such as treating relations as predicates on time-intervals:
 > (HasPart(x,y))(t)    (09)

Yes, that's another example of the open-ended range of ontologies
that may be useful for various purposes.    (010)

PH> Sure they [RDF and OWL] do [have the option of representing
 > extra arguments for time]. One simply has to use the (now standard)
 > trick of introducing 'facts' (not the best word) which have temporal
 > properties and also are systematically related to the arguments and
 > property of the predication. So the above becomes (there is fact of
 > type HasPart with the haver role being x and the having role being y
 > and the time-extent being t)    (011)

I admit that one can indeed define such constructions.    (012)

PH> In the N-triples notation for RDF this would look like this
 > _:x rdf:type HasPart .
 > _:x rdf:type PredicationFact .
 > _:x ex:whole X .
 > _:x ex:part Y .
 > _:x ex:timeTrue T .
 > Now, I will admit immediately that such a representation has its
 > problems: but it does actually work, if used consistently; and it
 > is systematic. In fact, if you think of the _:x here as being a
 > proposition, it can be viewed as a restricted subset of IKL.    (013)

But I still recall Guha's original argument for RDF as "simple".
And I cringe at the thought of what those N-triples would become
when expanded to the full XML form.    (014)

John    (015)

PS: Speaking of bloatware, have you seen the reports that Microsoft
is already testing a replacement for Vista with "key partners":
http://www.tgdaily.com/html_tmp/content-view-35641-118.html ?    (016)

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