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Re: [ontolog-forum] Visual Complexity

To: <matthew.west@xxxxxxxxx>
Cc: ontolog-forum@xxxxxxxxxxxxxxxx
From: Pat Hayes <phayes@xxxxxxx>
Date: Wed, 31 Jan 2007 13:22:32 -0600
Message-id: <p0623090ac1e695dfdf77@[]>
>Dear Pat,
>>  >Hi Everyone,
>>  >
>>  >... I do think, though, that some
>>  >measure of correction of logical constructions is probably also
>>  necessary,
>>  Amen to that. But it is very hard to see how this is to be done. I
>>  REALLY wish there were a nontrivial and useful notion of how to
>>  measure 'correctness' of an ontology. It is not enough to just say,
>>  it is correct if it "fits the facts" in some sense, since ontologies
>>  may be based on very different, possibly mutually contradictory,
>>  conceptualizations, and yet both fit the facts perfectly well.
>>  I have been worrying about this for years but have never managed to
>>  get my thinking to a point where it seemed useful to pursue an active
>>  research direction. If anyone has any ideas about it, I'd love to
>>  engage in a discussion.
>MW: Well I know I have views on this, so here goes.    (01)

I hoped this would happen :-)    (02)

>First, there are the basic quality principles:
>A quality ontology is "fit for purpose".    (03)

Great. Chris Menzel said something like this 
also. Now I want to know what a purpose is. Not a 
definition, but some entries in a list of 'uses 
for ontologies'.    (04)

>This means an absence of
>defects, which are what prevents an ontology from being fit for purpose.    (05)

Hmmm. That seems circular. What am I missing?    (06)

>An ontology that supported more purposes would be better than one that
>supported a subset of those purposes.    (07)

OK. Can I translate 'support a purpose' into 
'entails a set of sentences'? So that entailing 
more is supporting more? Im going to guess the 
answer is NO. So, what other kinds of purpose can 
it be used for? Or do you want to leave this 
open, and just take 'purpose' as a kind of token 
word for an open-ended set? (Which is fine, Im 
just asking.)    (08)

>Clearly at this level, as you point out, two ontologies can fit the facts
>but be wildly different. As the next level of differentiation I would
>look at the empirical/mechanistic degree of the ontologies. This distinction
>comes from mathematical modelling. Nearly any curve can be modelled by a
>polynomial expression, but this does not give you an insight into
>what is going on. On the other hand a mechanistic model is based on
>equations that give insight into how it works. I think the same principle
>applies to ontologies, and would be reflected in the degree and nature of
>the structure and axioms it contained.    (09)

That is interesting; so a good ontology provides 
insight as well as mere description? I agree that 
makes sense. And one might even approach 
measuring 'insight' by the number of useful 
extensions it has, or elaborations it supports (?)    (010)

What bothers me is that one man's insight can be 
another man's conceptual mistake :-) Barry thinks 
(what he calls) the SNAP/SPAN distinction is 
insightful, I think its a philosophical error. We 
aren't likely to agree on what counts as 
'structure', I'm going to guess :-)    (011)

>Finally, as a tie breaker I would appeal to elegance and simplicity.
>Admitedly, these are hard to pin down, but, given that, it is surprising
>how often people agree about what is more elegant/simple.    (012)

Yes, I have noticed that. And it seems to be 
largely independent of whether or not one thinks 
it is correct.    (013)

Thanks for the input.    (014)

Pat    (015)

>Matthew West
>Reference Data Architecture and Standards Manager
>Shell International Petroleum Company Limited
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