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Re: [ontolog-forum] Ontology similarity and accurate communication

To: "[ontolog-forum] " <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Pat Hayes <phayes@xxxxxxx>
Date: Wed, 19 Mar 2008 13:03:40 -0500
Message-id: <p0623090ac40702e95f1d@[]>
At 12:31 PM -0400 3/19/08, Patrick Cassidy wrote:
Cecil Lynch replied:
<CL> The problem here is that "Employee" isA "Role" and a "Role" is NOT a
type of person. It isA "Social Relation" or such and modeling it as a person
will lead to problems as you suggest, but this is a problem because of the
modeler, not the model. This makes the rest of the argument difficult to

No, in this ontology Employee is a subtype of both Role and Person. The
model permits multiple inheritance and is logically consistent.  There is no
logical problem in the model as described.

Perhaps not, but one needs more than this to understand it. Can you give us a reasonably pithy intuitive explanation of the conceptual picture underlying this approach? For example, what kind of thing is a role, that it can have a real person as an instance? In my mental model of roles, they are binary relations (or possibly unary functions), not people. So I have a lot of trouble following this; and I think Im not alone.

I also think this approach might violate some of the often-cited ontology construction best practices, such as identifying 'rigid' properties (those which something can lose only by ceasing to exist). Presumably a rigid property of an employee will not be the same as those of a person.

If it doesn't fit one's
preferences for use of particular word, then just substitute a Gensym for
the offending term.

Not good enough. Nobody can write axioms when they have no idea what the axioms are supposed to be saying.

The logic stays the same.
Of course the type "Role" is not a Person, neither is the type "Person" a
Role.  There are multiple subtypes of Role, and multiple subtypes of Person.
Employee is one of the subtypes of the Role type, and one of the subtypes of
the Person type.

The "problems", as I explicitly said, would only arise if one were to use
the types thus defined in an inappropriate manner.

Quite. But to be sure of not doing this, one needs to have some guidance about what is appropriate; and it has to make sense, to hang together intuitively.

 There is no problem in
the way they are used in the illustration.  One will have problems if one
uses *any* ontology element in a manner inconsistent with its logical

Once again, I would suggest that if one wants to assert some kind of problem
or inconsistency, please do it with an explicit set of logical assertions.
We can often resolve questions purely with language, but discussions of
logical consistency are especially susceptible to misleading interpretation
when we use words whose non-technical meanings get mixed up with the
intended technical meaning.

There are formal inconsistencies, which can be detected by logical machinery. But there are also what one might call mismatches, where a formal ontology, while internally consistent, fails to conform to a human user's intuition so strongly that it becomes incomprehensible to them. Typically this is what gives rise to formally incompatible ontologies, when they are separately developed by folk with these divergent intuitions.

Simply being internally consistent does not guarantee that an ontology is intuitive or even comprehensible.


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