William Frank wrote:
Pat, my point is that when you describe something, you are ipso
facto classifying it. That is just what a description does. It
specifies the set of things that fit the description, even if that is a
singleton.
I think what Pat is saying is that a
well-defined 'classifier' is a razor. You can apply it to decide
unequivocally whether a given thing satisfies it or fails to. A
'description' is not a razor. A 'description' is
merely some set of properties and observations that are true of the
object or category, and may or may not be sufficient to differentiate
the thing from other things that are similar but not intended.
In particular, I think you HAVE classified the thing, as
something locallizable in space and sherical in shape, and occupying a
particular position at a particular time. this distinquishes it from
Pakistan, topology, hurricane Dora, my brother, and many other things
that do not fit the classifier you created.
Indeed. But that is hardly the primary mechanism for distinguishing
basketballs from Pakistan, and it may or may not distinguish
basketballs from planets. The point of classifiers is to create a
set of well-defined categories for a certain domain
of interest.
Put another way, descriptions include properties the things are noticed
to have. Classifiers are necessary and sufficient properties for being
such a thing, which often do not include properties commonly appearing
in descriptions of such things.
To use a particularly NIST example, many properties of materials are a
direct consequence of the crystal structure of the material.
Therefore, a classifier for a material may specify its composition and
crystal structure, which is a hard razor, while a typical description
of the material will report its commonly observable physical
properties, or properties that have been empirically measured. While
the description is very useful for engineers contemplating the use of
the material for some particular purposes, those properties are not
necessarily distinctive of the material, especially in comparison to
its close relatives.
But, on reflection, I think my point was beside you all's
point.
Because you all are discussing rules for **constructing** an ontology,
and one of the rules is, we have a universe of discourse of atomic zero
order things, and each of those has to have a classifier that it fits.
Yes, in that many ontologies involve the development of rigourous
classification systems (where that is possible and appropriate to the
intended use).
So, this is a good rule for the completeness of an ontology,
only it is
not a rule about the world, where everything DOES have a classifier. It
is a rule about how to build a human aritifact, a formal ontology.
I don't follow. It seems to me that "things of interest" to a given
sentient group have "classifiers" imposed on them by that sentient
group. But there are many things that don't have classifiers other
than "uninteresting thing" or "something I never heard of" except for
vary narrow interest groups. And in many cases, we tend to be utterly
unaware of the existence of things outside our ken.
-Ed
"There are more things in heaven and earth, Horatio, than are dreamt of
in your philosophy."
-- a different William (Shakespeare), "Hamlet, Prince of Denmark"
--
Edward J. Barkmeyer Email: edbark@xxxxxxxx
National Institute of Standards & Technology
Manufacturing Systems Integration Division
100 Bureau Drive, Stop 8263 Tel: +1 301-975-3528
Gaithersburg, MD 20899-8263 Cel: +1 240-672-5800
"The opinions expressed above do not reflect consensus of NIST,
and have not been reviewed by any Government authority."
Wm
>
> Pat Hayes
>
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>
--
William Frank
413/376-8167
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