Re: [ontac-forum] Future directions for ontologies and terminologies

[Lucian_Russell/ESI/CSC <Lucian_Russell/ESI/CSC@xxxxxxx>]

Static vs. Dynamic Queries

Hello from a former lurker. My
name is Lucian Russell and my specialty is applying the principles of uncertain
reasoning to data, all kinds. I have been in the computer science field
for several decades.

One of the decisions one needs
to make about an upper Ontology is whether it is needed at all.  If
the answer is “yes” then the choice is to create a single upper Ontology
that categorizes all human knowledge into a small number of categories.
This is by definition static. The other alternative is to have a large
number of categories which can be combined on the fly; this is by definition
dynamic. This decision entails recognizing the form it would take.  

This initial submission will lay
out one issue: the need or not for concept lexicalization for the highest
level of a static Ontology. As John Sowa cited the philosopher Aristotle’s
timeless insight, I will cite the timeless insight of Gloria Estphan who
in the 1980s sang the hit “The Words Get in the Way”. 

First off, let me recommend to
those who know of WordNet but have never read the book to do so, especially
Chapter 1 (nouns) and Chapter 3 (verbs); subsequently read Chapter 2 (adjectives
and adverbs) and re-read the two surrounding chapters. To those who have
read the book, congratulations for being so well organized and prescient.
For those not following WordNet it is up to Release 2.1 and is completing
a mapping of words in explanations to senses in WordNet. This latter work
will be finished up in April. The current release is available for downloading;
it is also on-line for any single word. 

Prof. Christiane Fellbaum is the
current Principal Investigator (PI) on the WordNet project (Prof. George
Miller who started WordNet is old enough that I had him as an instructor
for a General Education course while an undergraduate, so is no longer
working full time).  She makes the following distinction between WordNet
and other Ontologies. WordNet is a lexical ontology. That means that it
is based on words in the English Language, though some noun phrases are
also included (the words are separated by the underscore character). Although
this is generally true, even WordNet contains some non-lexicalized nodes,
which brings me to the key question:

1. Should a class name in an Ontology,
especially an upper level class, be restricted to a word or phrase?

It would seem that there is something
to be said on both sides of this issue. 

On the “no” side, for example,
WordNet shows that in English verbs there are two senses of the verb “move”.
One is movement with a translation in space and one is movement without
this change in special position (e.g. spinning). The two senses are not
lexicalized but are rather distinct senses of a word with a given spelling
(homograph).

On the “yes side” if for a static
Ontology there is a single word (or a well known noun phrase) that is used
for the name of a class then we have a sound basis for looking at sub-classes
and the class membership of instances. In this case we say that the concept
is lexicalized.  

A further “yes” argument is that
if a concept in the Ontology is not lexicalized then we have to create
a name for that concept’s class. But to name it is not to claim it: we
cannot claim that our work is done just because we have stung two or more
words together. Lacking a linguistic history of our new phase we need to
either (1) enumerate the subclasses (in set theory an extensional description)
or (2) define a set of inclusion rules (in set theory an intensional description).


Of course we could lexicalize the
concept by taking a word from another language that does lexicalize the
concept, but if the Ontology is meant for English speakers that new word
still needs to be explained to them (the same is true for any language
whose words are used to name concepts). 

In practice the class membership
criteria for instances of an Ontology are specified by a set of constraint
rules on property values. Using Descriptive Logic one must be able to reason
about the assertion “if X is a class and x in an instance of a thing with
property values (a1, a2 …..an) then x is a member of the class X “. The
answers are “Yes” and “No”. So for an Ontology a non-lexical class
name is really a substitute for a mathematical description. 

Static Ontologies, therefore, should
probably be ones that primarily use lexicalized concepts in classes. That
being the case, it would seem that the logical consequence is that for
the top Ontological categories one should use WordNet’s “beginning names”
unless there was a REALLY good reason not to do so. 

Some researchers in Artificial
Intelligence claim they have a better top level Ontology, and maybe they
are justified. However, WordNet has some 15 years behind it, so the set-descriptions
of the any different concepts should be carefully spelled out so that we
may judge.

In the end we can choose what we
want; we just should be sure of why we made the choices and know the consequences.


If I have repeated well worn arguments,
I will take my deserved newbie lumps and be suitable chastened :-)

Lucian Russell, PhD
___________________________
Lucian Russell, PhD
Sr. Architect - Principal
Federal Consulting Practice
Computer Sciences Corporation
3110 Fairview Park Drive 
Falls Church VA, 22042
Ph: (703)-645-5237
Fax: (703)-645-5233
Cell:(703)-340-5807


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