>On Feb 12, 2007, at 12:12 PM, Pat Hayes wrote:
>>> You're right that import statements should not be considered part of
>>> an ontology. I agree it's the imported axioms that are part of the
>>> ontology.
>>
>> Wait. Of course the imports statements are part
>> of the ontology. What are you guys talking about?
>
>*If* ontologies are logical theories (01)
Well, if "theory" has to mean deductively closed,
then I would say no, they are not. That is, an
ontology to me means a set of sentences (usually
finite, usually not deductively closed) in an
ontology language. Which is, roughly, a formalism
with a model theory. (02)
>, then it seems to me that this
>confuses a mechanism for saying what (some of) the axioms of an
>ontology are with the ontology. (03)
Why do you call this "confuses"? The assertion of
what some of the axioms are can be part of the
theory. You seem to be insisting on a 'levels'
distinction here which I fail to see the reason
for (and plenty of reasons to reject.) BTW, Cyc
has been doing this for years. (04)
> Suppose I'm writing my ontology for
>TAMU faculty and admin again, and you've got a nice higher-level
>ontology for universities over there at IHMC. My statement "import
>(reiterate, endorse, whatever) Pat's university ontology" is not part
>of my ontology (05)
YES IT IS. Check out the specs. In both OWL and
CL , the imports is a *sentence*, and the
truth-recursions apply to it like any other
sentence. True, they involve paying attention to
some rather unusual non-traditional matters, like
network identifiers denoting theories; but they
are sentences, and they are part of the ontology.
They are not in some other meta-level, they are
not written in a different language, and they are
not a mechanism. Their meaning is specified
semantically, not operationally. (Tamel even
suggested allowing imports sentences to partake
in the usual sentence recursion, so one could
have conditional or quantified import sentences.
In IKL we could make the identifier denote the
proposition expressed by the ontology, but CL
wasn't ready for that, so we didn't bite that
particular bullet.) (06)
>; it's a mechanism for saying what my axioms are that
>makes efficient use of an open network.
>
>I'm not dogmatically wedded to the idea that formal ontologies are
>logical theories of some ilk, but if you're right, and my import
>statement is literally part of my ontology, then formal ontologies
>are not (in general) logical theories, (07)
Well, it depends on what you count as a logic, I
guess. Is CL a logic? Because CL has importing
with a full model theory, cf. section 6.3 in the
ISO final draft (08)
http://cl.tamu.edu/docs/cl/24707-31-Dec-2006.pdf (09)
See also lines E17 and E20 in the semantics table
in 6.2. As I put quite a lot of work into
getting this (I hope) right, I guess I am rather
unwilling to admit that it is broken or
irrelevant. (010)
>and we'd better get clear
>about the connection between the former and the latter. You seem to
>be favoring the idea that ontologies are rather more concrete than
>I'd been thinking. Do you think it would be better to say that a
>logical theory is only one of several components of an ontology? (011)
See above. Whatever we decide should be the
definition of "ontology" (God alone knows why we
need a definition, but...), it had better be the
case that the 10,000 or so existing OWL
ontologies turn out to be ontologies by our
definition. Now, *they* are collections of
assertions in OWL (or maybe the XML documents
which encode those assertions, or the RDF graphs
which encode..., etc.; choose your favorite
encoding level). These are finite entities and
their sentences satisfy semantic constraints
which fully determine their meanings. And the
'imports' sentences that they contain are part of
them, just as much as any other sentences. I'm
happy to say that they are sets of logical
sentences, myself. (012)
Pat (013)
>
>-chris
>
>
>
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