Leo, I would like to volunteer to capture all of the notes concerning the "Dimensions/Aspects" of ontology types. For now, I'll leave the "Logical Theory(?)" topic to someone else . . . The topic interests me a great deal, and as I've already contributed at least two potential dimensions to the conversation, I would like to see it continue and be recorded. Chuck Charles Turnitsa Project Scientist Virginia Modeling, Analysis & Simulation Center Old Dominion University Research Foundation 7000 College Drive Suffolk, Virginia 23435 (757) 638-6315 (voice) (757) 686-6214 (fax) cturnits@xxxxxxx
-----ontology-summit-bounces@xxxxxxxxxxxxxxxx wrote: -----
To: <gruninger@xxxxxxxxxxxxxxx>, "Ontology Summit 2007 Forum" <ontology-summit@xxxxxxxxxxxxxxxx>
From: "Obrst, Leo J." <lobrst@xxxxxxxxx>
Sent by: ontology-summit-bounces@xxxxxxxxxxxxxxxx
Date: 28/01/2007 06:41PM
Subject: Re: [ontology-summit] dimensions/aspects of ontology types?
I think we need to capture these notions in the wiki. It will be
difficult but, I hope, possible.
Peter, what do we need to do to accomplish the above?
Because we are at the (relative) beginning of our discussion, I'd like
to ask for topic volunteers who would capture our evolving notions
about these notions. Note that they can be just quick notes and
extractions from emails now. These may evolve toward coherent notes,
form the bases of potential statements eventually: who knows?
Unfortunately, email doesn't capture discourse.
Thanks,
Leo
ps. Any volunteers? Maybe by topic? Ontology as logical theory.
Dimensions/aspects of ontology types? There will be more; in fact,
propose others.
Expressiveness and complexity of modeling language vs. complexity of
computation performed on content in that language?
_____________________________________________
Dr. Leo Obrst The MITRE Corporation, Information Semantics
lobrst@xxxxxxxxx Center for Innovative Computing & Informatics
Voice: 703-983-6770 7515 Colshire Drive, M/S H305
Fax: 703-983-1379 McLean, VA 22102-7508, USA
-----Original Message-----
From: ontology-summit-bounces@xxxxxxxxxxxxxxxx
[mailto:ontology-summit-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Michael
Gruninger
Sent: Sunday, January 28, 2007 6:25 PM
To: Ontology Summit 2007 Forum
Subject: Re: [ontology-summit] dimensions/aspects of ontology types?
Hi Bill,
Quoting Bill Andersen <andersen@xxxxxxxxxxxxxxxxx>:
> Hi Leo...
>
> I have some comments about some of these proposed dimensions..
>
> On Jan 28, 2007, at 14:40 , Obrst, Leo J. wrote:
>
> > Dimensions of Ontology Types:
> >
> > 1) Formality: Informal (Formality = 0) vs. Formal (Formality = 1)
>
> I don't quite get what this means. If we're not talking about
> artifacts that are somehow used to influence software to do things we
> want, I don't see the point. So, for some thing O, if Formal(O)
> means that O is a logical theory, then, following ChrisM, I don't see
> what anything not formal should even be considered, since otherwise,
> it would be pretty close to impossible to say how it could be used
> for some computational end.
The ecumenical definition of "ontology" that Mike Uschold and I have
used is:
"An ontology includes a vocabulary of terms together with a
specification of
the intended meaning of the terms."
Different approaches to ontologies are distinguished by the latter
condition,
that is, in the way that they specify the intended meanings.
Leo is pointing to a basic partitioning of these approaches.
A formal ontology is a set of sentences in a language that has a model
theory,
that is, a notion of interpretation that supports truth assignments,
satisfiability,
and entailment.
(As observed by recent discussions, this is a necessary but not
sufficient
condition,
since there are sets of sentences that not everyone would consider to
be an
ontology,
but this is not my point here).
On the other hand, the specification of intended meanings in an
informal
ontology relies on
extralogical mechanisms (natural language, diagrams, canonical software
implementations).
The line does become a little blurry when the expressiveness of the
underlying
logical language
for an ontology is insufficient to axiomatize the intended
interpretations of
the terms.
For example, in OWL-S (the OWL ontology for web services), different
classes of
processes
such as Unordered,Sequence,etc are axiomatized in OWL.
Nevertheless, OWL is not expressive enough to capture the full intended
interpretations
of these classes, which is specified in natural language as
documentation.
>
> > 2) Expressivity: Expressivity of the semantic model (i.e.,
underlying
> > knowledge
> > representation language or logic) [No scale determined yet]
>
> This is a property of a logical system, independent of the instances
> of which we wish to regard as "ontology", so I'd exclude this
dimension.
It is a property of a class of structures AND the logical language.
There are classes of structures that are not first-order definable,
and classes of structures that are not definable in DL.
This is an important issue because we need to be able to determine
whether the intended interpretations of the terms in the ontology
can be defined within the advertised formal language.
- michael
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