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Re: [ontolog-forum] Levels

To: Kathryn Blackmond Laskey <klaskey@xxxxxxx>
Cc: "[ontolog-forum] " <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Pat Hayes <phayes@xxxxxxx>
Date: Mon, 12 Feb 2007 14:19:23 -0600
Message-id: <p06230904c1f65c218f84@[]>
>>As I have said many times, I have no objection whatever
>>to saying that microtheories are part of the ontology.
>To clarify, by "the ontology," you emphatically do NOT mean the same
>thing as what your previous email called the "base ontology (i.e.,
>what is usually called the 'upper level').
>You are distinguishing among several levels:
>   - Upper ontologies such as sets, arithmetic, space and time, ...
>   - A base ontology for a domain such as medicine.
>   - Microtheories for particular sub-domains, such as theories
>     about particular diseases. You have said you're willing to
>     call these "extended ontologies".
>Am I tracking you?    (01)

I think the terminologies are getting rather 
scrambled here. I have no idea what is meant by 
'base', but 'microtheory' is a term of art: it 
refers to a comparatively small 'context' logical 
theory used to narrow down the the attention of a 
logical reasoner to a relatively small set of 
axioms, and possibly also to narrow the sense of 
one or more concepts to a particular sense (so 
that the axioms for "bank" in a financial context 
will be in one microtheory, while different 
axioms for "bank" will be found in a microtheory 
devoted to aircraft dynamics, say). "Microtheory" 
is often treated as a synonym for "context" .    (02)

>Practitioners use the word "ontology" for all three, and may not
>differentiate among levels.  This creates some of the very problems
>ontologies are supposed to solve.  For example, we don't want a
>medical ontology contains highly specialized axioms for calculating
>dosages of drugs from patients' weights, which turn out on careful
>analysis to be reinventions of arithmetic.  It would be much better
>to have the medical ontology reuse a standard ontology for arithmetic.    (03)

Er... why 'standard'? I suggest that we never 
think of ontologies (as opposed to ontology 
languages) as 'standard'.    (04)

>I'm in agreement that we need different levels.  Some purists argue
>that only the uppermost level deserves the name ontology.  But the
>engineering community seems to have co-opted the term and given it a
>much broader meaning.    (05)

It always has had the broader meaning; I don't think that your 'purists' exist.    (06)

>  It's probably not possible to close Pandora's
>box now.  So we need to differentiate the levels.    (07)

This really isn't clear. It isn't even clear that 
there are well-defined 'levels'. What use is this 
'levels' notion? What utility does it provide? I 
can see all sorts of ways it might cause harm 
(e.g. if one is obliged to classify an ontology 
into some predefined 'level') and none in which 
it is useful. Suppose I know that on ontology is 
one of those in level 3 (say). How does that help 
me use the ontology better, or affect the meaning 
of anything in it?    (08)

>Should we go for "upper ontology", "base domain ontology", and
>"extended domain ontology"?
>These questions are entirely orthogonal to the question of whether
>ontologies should be formalized in classical logic, probabilistic
>logic, or some appropriate combination for the purpose.
>>   > SUMO hasn't been officially adopted yet, has it?
>>I don't know what you mean by "adopted".  A lot of people
>>use it.  I think that SUMO, Cyc, and many other ontologies
>>are quite good for their purposes.
>>But the fact that there are multiple widely used ontologies...
>That's what I meant.  There are multiple widely used ontologies even
>at the "upper" level where you said all reasonable people were
>supposed to agree.
>The point I was making was was that reasonable people don't agree.    (09)

Indeed. Which is why we shouldn't try to standardize them.    (010)

>>implies that any common upper level should contain only
>>the intersection, not the union of them.
>Is the intersection non-empty?    (011)

Good question. I suspect it is nonempty but *extremely* small.    (012)

>Wouldn't you want to require your ontology to explicitly name the
>ontologies from which it was drawing terms?    (013)

The SWeb has an answer to this, which is that all 
ontology names are global (are IRIs or 
UIRreferences), so there is no notion of 'drawing 
names from'. Any name can occur in any ontology. 
And, by the way, ontologies do not *define* 
names: they make assertions using them.    (014)

>Otherwise, we could have
>any number of meanings assigned to the terms not defined in the
>ontology, if there were multiple external ontologies that defined
>them in conflicting ways.    (015)

Ignoring the 'define' words: yes, that is 
correct. You can have this situation (other 
ontologies use names which all occur in ontology 
A and make further assertions about them which 
are not all consistent with one another.) Get 
used to the idea.  There is absolutely no way to 
prevent this happening on an open network. It 
could be a terrible problem, in a theoretical 
worst case. It does not in fact seem to be a real 
problem in practice, for essentially 
social/network/economic reasons.    (016)

Pat    (017)

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