Sandro, Bill, Richard, Hans, Alex, Joel, and Hassan, (01)
There is a big difference between guidelines and requirements. In most
cases, a guideline that permits exceptions is more useful than a strict
requirement or prohibition. Ontology is still a research area with many
unsolved, poorly defined, or even unknown problems. We cannot predict
what may happen to be useful, successful, or required in the future. (02)
SRF
> ... it seems that there is a general agreement that "ontologies can
> have individuals, but only in special cases". (03)
Yes, but I don't believe that we have considered, analyzed, and
precisely specified all the kinds of special cases. (04)
SRF
> I would add that, besides being necessarily true, facts about specific
> individuals can be present in an (domain) ontology only if they are
> shared by the community. (05)
This statement involves too many constraints such as "necessarily true",
"can be present", and "only if". And the term 'community' is much too
vague to be dependable. That statement might be useful as a guideline,
but not for a definition, standard, or requirement. (06)
WA
> I sympathize with your intuition, but it would take some work to
> pin it down precisely. (07)
Bill made this statement in response to Nicola, but it could be applied
to almost every general principle proposed in this thread or email list. (08)
RD
> uniqueness is a very important point to support mathematical analysis. (09)
Yes. That is why functions are important in mathematics and logic.
Whenever you have a function, say x=f(y,...,z), it implies that there
is exactly one x for every combination of the arguments y,...,z. (010)
HP
> Don’t forget that identifiers for individuals are grounded in institutional
> frames of reference with context and scope. (011)
Yes. Every system of unique identifiers specifies a function from
a set of individuals in the universe of discourse to a set of symbols
that somebody chooses to call "identifiers". In practice, implementing
such a function and guaranteeing uniqueness is a non-trivial exercise. (012)
AS
> does anybody have Tbox with individuals? (013)
The term 'Tbox' has never been precisely defined. But any geographical
information system must make provision for special individuals called
the earth, sun, and moon. It must also include many facts about them.
For example, the earth is an oblate spheroid, the moon revolves around
the earth, and the earth-moon system revolves around the sun. (014)
Any ontology for geographical information systems that did not include
those individuals and many such facts about them wouldn't be useful. (015)
JLC
> I wonder if can we commit ourselves to an ontology that does not
> distinguish between types and tokens. (016)
Peirce used the type/token distinction in talking about signs. That is
an important topic. But when we're talking about ontology, it's better
to use metalevel terminology that is directly related to the logic. (017)
To use Quine's criterion, the things that exist in your ontology are
those you can refer to with a quantified variable. Then types are
specified by monadic predicates. Some logics let you use variables
to refer to types (monadic predicates) -- that allows types of types. (018)
HAK
> Why has a specific formalism terminology (namely OWL's TBox, ABox, ...)
> become standard? There have been generic names (Schema, Database,
> Knowledge Base, ...) independent of any specific formalism - as it should be. (019)
Yes. The field of ontology -- more generally, knowledge representation
-- has a large number of terms that are almost synonyms. In fact, every
notation introduces a set of terms that are not quite the same as the
terms used with other notations (even when they have the same spelling). (020)
I prefer to start with a minimal vocabulary for logic: 'and', 'not',
'there exists', and either 'relation' or 'predicate' with the option
of zero or more arguments for each relation or predicate. Then
everything else can be defined in terms of those words. (021)
John (022)
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