As a geographer, I find this discussion interesting although most
geographers would not argue about what a river is - there are
(numerous) very well defined vocabularies and ontologies for
physical features on the earths surface. The would argue more about how to
photo-interpret the river (low water, high water, centerline etc).
The real issue is to figure out how to map between these the various
ontologies to foster data sharing greater interoperability between and
among communities. This, for example, is why the OGC community and the hydrology
community have initiated more intense interactions.
----- Original Message -----
Sent: Monday, February 16, 2009 1:08
AM
Subject: Re: [ontolog-forum] a skill of
definition - "river"
@ John,
I appreciate Waismann's point. I don't think what I said is in opposition
to it, as far as i can tell, it embraces it. Though I like to get at his
insight by thinking that once specified, any system begins to decay.
Suggesting then simply that maintenance / upkeep / revision is a
necessary part of any specification framework.
@ Matthew
Oops. Thanks for clarifying, I was confusing senses of extension
:P.
or whether one
particular ontic category hierarchy is appropriate for all, I think efforts
would be more fruitful in explicating / generating mappings between what
various peoples find useful. I.E. take the IDEAS hierarchy and compare
it to DOLCE or SUMO -- what's being reused?
[MW]
Wrong question. More important is how do you map from one to the
other.
I think those questions (reuse) are part of the process of understanding
and developing such mappings.
[MW]
Well the way this normally plays out is that those who take an intensional
approach do not necessarily think they have something different when the
membership of a set changes. So If I ask "How many cars are there". They
will give a certain answer, and if I ask the same question a year later,
they will give a different number, and will be quite happy that the
membership of the set has changed. An extensionalist, on the other hand,
will insist that these are actually two different sets: Cars-at-time-1 and
Cars-at-time-2, and a 4D extensionalist will say that the set of all cars,
is all the cars that have existed and will exist.
So each ontology interprets the notion of set differently, which affects
the notion of a definition.
Forgive me if what I say is obvious, but for posterity, in the above we
have a statement, "set of all cars" which corresponds to three distinct sets,
depending on what framework one employs.
Let's call them:
Sint - intensional
Sext -
extensional
S4Dex - 4D extensional
which are unique.
So in an intensional framework, depending on when a query is executed (a
question is asked), Sint= Sext@Tquery.
In a 4D extensional framework, set S4Dex = U (forall i) Sext@Ti
where @Tx
is the unique name of each set in the extensional perspective at time x.
Seemingly, the above suggests that if we want mappings to work, while
each group may choose their own framework, if they intend to interoperate, we
need to know what pieces of information we need to track (though perhaps not
ontologically commit to), to enable such mappings. Thus if using an
intensional framework, with an eye on translating to an extensional one, we'd
need to track when extensions are generated, etc.
Is this a semi-accurate catch-up to where people thinking about this
issue are?
Ali
On Mon, Feb 16, 2009 at 2:19 AM, John F. Sowa
<sowa@xxxxxxxxxxx> wrote:
Ali,
Mitch, and Frank,
AH> If you've given a definition of River, and
it is inadequate
> when you encounter something as the Okavango River, ought
it
> not indicate that you only need to update your definition
of
> river? Isn't the whole point of defining something trying
to
> abstract the generalizable qualities / properties of
the
> object/entity under consideration? You can still have
a
> monotonic logic, you just need smart revision
policies...
It's always possible to legislate a definition and to
revise
the definition whenever you encounter an exception. But
the
point of Waismann's notion of 'open texture' is that there is
no
stopping point. If you arbitrarily choose a stopping point,
you
will inevitably exclude unanticipated cases that are just
as reasonable
as the ones you do include.
That is a serious problem for any legal
system. Any system
of laws has inevitable exceptions and borderline
cases that
require a judge and jury to decide.
--
(•`'·.¸(`'·.¸(•)¸.·'´)¸.·'´•) .,.,
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