Chris, (01)
On Fri, 2010-12-24 at 13:54 -0600, Christopher Menzel wrote:
> On Dec 24, 2010, at 9:58 AM, Patrick Durusau wrote:
> > ...My point is that useful ontologies are not limited to those constructed
>based on formal logic and avoidance of modeling mistakes.
>
> So, if I understand you, Patrick, your point is that
>
> (D) There can be useful models that are either (a) not based
> on formal language or (b) contain modeling mistakes.
>
> Before addressing that, let's first be sure that we mean the same thing by
>"based on formal logic." By that I certainly don't mean an ontology that is
>written in an explicitly formal language like CLIF. There are, in particular,
>some very nice, user-friendly graphical languages that are entirely rigorous.
>To say that a language for constructing ontologies is based on formal logic is
>only to say that the language has a sound logical foundation -- specifically,
>the syntax of the language must be clearly defined (so that well-formed
>constructs can be clearly distinguished from ill-formed) and the basic
>constructs of the language must have a rigorous semantics so that assertions
>in the language can be meaningfully interpreted. (Both are necessary, in
>particular, if the ontology is going to be subject to any sort of useful
>automated reasoning.) A well-designed tool like Protege will simply
>incorporate those logical foundations into the tool itself and a user will
>adhere to them simply in virtue of using the tool. So to say ontologies must
>be "based on formal logic" is only to say that the representation language of
>the ontology meets strike me as entirely minimal standards of rigor and
>coherence.
>
> Given this, part (a) of your thesis (D) is that there are, or at least can
>be, useful ontologies such that either it is not clear what is a well-formed
>construct of the language and what isn't, or it is not clear what the meanings
>of its basic constructs are. I wouldn't want to go so far as to say such an
>ontology could not be useful in some very limited way; perhaps in a small
>organization in which people can clarify what the ontology is supposed to mean
>with verbal explanations and where there is no need for the ontology to be
>shared by others outside of that small setting. So let me revise my claim to
>be that ontologies "not based on formal logic" are useful at best in some very
>limited setting.
> (02)
I think we agree that "based on formal logic" does not involve questions
of representation or syntax but your "entirely minimal standards of
rigor and coherence." (03)
My claim is that useful ontologies can exist that violate your "entirely
minimal standards for rigor and coherence." (04)
When you say such ontologies "...are useful at best in some very limited
setting" what puzzles me is the lack of adoption of formal ontologies
that would meet your "entirely minimal standards...." (05)
Yet, we know that ontologies (in the broad sense of the word) are in use
in databases around the world, for instance, that I suspect have
numerous formal modeling errors. (06)
> As for part (b) of (D), I have to say I am nonplussed. What do you have in
>mind? Obviously, it is unlikely that any large ontology with be completely
>free of modeling errors, but surely the usefulness of an ontology is inversely
>proportional to the extent of its errors.
> (07)
Not really, depends. Much like a software program that doesn't catch
buffer overflows can be quite useful, so long as no input causes the
buffer overflow condition to obtain. (08)
Depends on where the errors in the ontology are to be found. (09)
> > I happen to agree that construction of logic based ontologies requires
> > more than "...a clear head, a bit of common sense, and a copy of
> > Protégé." Having said that, I would not exclude ontologies developed
> > without a formal logic basis from being ontologies.
>
> Oh, that's a different claim. I myself would have no problem saying there
>are ontologies that are not based on formal logic in the sense above. I would
>simply say, once again, that they are, at best, marginally useful or, at
>worst, incoherent.
> (010)
It is the claim that ontologies not based upon formal logic (in the
sense we agree on above) are "...marginally useful or, at worst,
incoherent" where I disagree. (011)
I hear those as separate claims. (012)
1) Such ontologies are "marginally useful." I am not sure we would agree
on "marginally useful" but suspect it might be possible to collect
evidence of ontologies that meet the criteria for "not being based on
formal logic." What judgments we would reach on their usefulness would
have to await such a collection process. (From the indictments in this
forum, it should not be a tough collection process.) (013)
2) Such ontologies are "incoherent." See my buffer overflow argument
above. Not sure that is an indictment. (014)
What happens if an ontology based on formal logic is found to have a
fundamental error that is seldom encountered. Does its later discovery
invalidate results up to that point? Does it then become incoherent? (015)
Hope you are having a great evening! (016)
Patrick (017)
> Chris Menzel
>
>
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