Dear Pat, (01)
Some clarifications below. (02)
> -----Original Message-----
> From: Pat Hayes [mailto:phayes@xxxxxxx]
> Sent: 31 January 2007 19:23
> To: West, Matthew R SIPC-DFC/D21
> Cc: ontolog-forum@xxxxxxxxxxxxxxxx
> Subject: Re: [ontolog-forum] Visual Complexity
> >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
> >> 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.
> I hoped this would happen :-)
> >First, there are the basic quality principles:
> >A quality ontology is "fit for purpose".
> 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'.
> >This means an absence of
> >defects, which are what prevents an ontology from being fit
> for purpose.
> Hmmm. That seems circular. What am I missing? (05)
MW: Nothing. Defects are just the other side of the same coin.
> >An ontology that supported more purposes would be better
> than one that
> >supported a subset of those purposes.
> 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.) (06)
MW: Well this was in the sense that the ontology is useful
(or not) for some purpose, which might loosely be interpreted
as an application (class). Notice I am stepping away from
correctness here. I'm fairly happy that whilst you can sometimes
prove something is wrong, it is pretty much impossible to prove
something is correct. An absence of evidence that something is
incorrect (absence of defects) is the best we can generally do. (07)
MW: Examples of applications might be:
Answering questions based on common sense/common knowledge
Supporting the design of engineering artifacts
Supporting medical diagnosis
Providing a foundation for more specific ontologies
> >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.
> 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 (?) (08)
MW: This is what Chris Partridge at least likes to call fruitfulness.
A good ontology will often have things in it that turn out to be
unnexpectedly useful, and apply in places and ways that were not part
of the original intent, because of the depth they have.
> 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 :-) (09)
MW: Well I agree with you here ofcourse about the coneptual mistake. But
I think you are more likely to get Barry under simplicity/elegance,
because he has to duplicate a lot of stuff, such as a person becuase he
has to have two objects, one the physical object, and the other the
lifetime activity, and presumably a relationship between them. (010)
MW: Again, I think looking for unexpected fruitfulness is the measure.
> >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.
> Yes, I have noticed that. And it seems to be
> largely independent of whether or not one thinks
> it is correct. (011)
> Thanks for the input.
> >Matthew West
> >Reference Data Architecture and Standards Manager
> >Shell International Petroleum Company Limited
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