Not sure how well this will be received, and the idea is not 100% mature,
but I've been playing with (what appears to be) a useful set of definitions
for type, class and set. (01)
Type - a categorization of entities (both objects and process), where
similar instances are grouped together based on some common (agreed to)
organizing concept agreed to by the users of the domain. A simplistic
example might be - In the domain of animals there is a type known as
"Mammal", all of the instances of that type share the same properties that
conversants in the domain think of as being definitional of Mammals. (02)
Class - a categorization of entities (objects and process, types and
instances) that are grouped together to serve some semantic or grammatical
purpose. In a grammar, of course, you have a number of non-terminal
symbols that represent "things" from your language that serve a useful role
in the grammar (nouns, verbs, pronouns) in different situations. This is
what I'm thinking of here. Classes are important for establishing rulesets
(such as grammars) on the contents of your ontology. For instance, "the
class of all objects, types and instances, that can be related to location
X at time Y". (03)
Sets - any other ad hoc categorization that a conversant within the domain
of the ontology wishes to make. For instance, the set of all animals that
a young girl thinks are cute. Or the set of all governmental agencies that
might be interested in funding Ontology research. : ) (04)
By my definition, the categorization that I refer to as Type belongs within
a formal ontology. The categorization that I refer to as Class is used by
the rules of discourse that a conversant in the ontology's domain might
use. And the categorization that I refer to as set are just convenient
methods of grouping things together as the conversant sees fit. (05)
Chuck (06)
Charles Turnitsa
Lab Manager/Project Scientist
Virginia Modeling, Analysis & Simulation Center
Old Dominion University Research Foundation
7000 College Drive
Suffolk, Virginia 23435
(757) 638-6315 (voice)
(757) 686-6214 (fax)
cturnits@xxxxxxx (07)
ontac-dev-bounces@xxxxxxxxxxxxxx wrote on 01/27/2006 04:25:05 AM: (08)
>
> > >
> > > Leaving aside administrative domains (e.g. tax collection), types,
> > > like instances, are discovered. They are out there in reality. They
> > > form the subject-matter of scientific inquiry.
> >
> >MW: Well I would say that there is an abundance of sets out there and
> >some of them have greater significance than others.
>
> Interesting to find out why some have greater significance than others
...
>
>
> >BS> Quine used to talk about desert landscapes. You, it seems, are
pining
> > > for desert landscapes from which all traces of the biological have
> > > been eliminated (even, I suppose, the oil and gas underneath).
> >
> >MW: Quite the reverse, I am saying there is every possible set you can
> >imagine (and probably more) and that you are just identifying some as
> >useful for some purpose.
>
> Analogously there is every possible combination of human bodily
> parts; there is Matthew's nose plus John's legs plus Patrick's feet
> (etc.); Patrick's nose plus Leo's legs plus Chris's feet (etc.);
> Matthew's nose plus Matthew's legs plus Matthew's feet (etc.). And
> all have equal civil rights, but you are just identifying some as
> useful for some purpose.
>
> This is silly.
>
> > >
> > > >MW: My problem now is that I understand that you want types to be
> > > >restricted to things like rabbits, not "people with 376
> > > hairs on their
> > > >arms" or "4, the moon, and me". Now, whilst I am sympathetic
> > > >to the idea of natural kinds, it seems to me that these
> > > three examples
> > > >actually sit in a spectrum and there is no clear divide between them
> > > >(though these three being prototypical can be easily distinguished).
> > >
> > > There are many terms for which we have clear examples of entities
> > > which fall under them, clear examples of entities which do not fall
> > > under them, and then a penumbra of problematic cases in between.
> > > Responses to this problem for 'type' might be:
> > >
> > > 1. it is hard work to find out which types exist (this work is called
> > > 'science') (BS)
> > > 2. we should refrain from formulating axioms about what is a type
(JS)
> > > 3. 'type' is redundant; we should talk of sets instead, keeping our
> > > heads under the desert sand to avoid all sight e.g. of
> > > anything biological (MW)
> >
> >MW: Well as usual you indulge in gross misrepresentation when all else
> >fails.
> >
> >MW: In a 4D world I am happy to concede that there will be a set of sets
> >that corresponds to what you would refer to as types. (With an abundance
> >of sets of course its there). In your 3D world you seem to need these
> >things to be able to have varying membership over time. That is simply
> >a problem I don't have.
>
> Indeed. I take it that you when were doing arithmetic tests in
> school, your answer would always have the form: "There is an
> abundance of numbers out there, one of which is the correction
> solution to this problem."
> BS
>
>
> >
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