Where to start (was: Ontology for Dummies)

[Bernard Vatant]

A little more about TM, to follow-up with Sean

*Tony Linde:
> > I don't want to spark an OntoWar, but could people (participants and
> > lurkers alike) say if there is any significant difference between a
> > topic map approach to ontologies and an OWL (or its ancestors') language
> > approach.

* Sean Bechhofer
> Topic Maps and OWL (hereafter referred to as TM and OWL to save
> typing) *are* different. This is not to say that one is "better" than
> the other though -- they are *different*, and are suitable for
> different purposes. TMs provide a kind of model of "back of the book
> indexes", a way of indexing particular occurrences of topics or
> subjects. In my opinion, they are not a framework for representing
> ontologies (** see below).

This is controversial, even TM folks are not quite clear on that.
TM are a framework for representing taxonomies and semantic networks.
What is missing (so far) is the constraint and inference layer.

> Again, in the interests of world peace and
> harmony, this is not intended as a diss or put-down of TMs -- there
> are other things that TMs will do better than an approach like OWL.

Agreed :)  But could you expand on what you expect TM to express better than OWL?

> OWL is a language and framework for representing ontological knowledge
> and information about the way that the world is structured and fits
> together. As such it has a well-defined semantics (in terms of a model
> theory) that allows us to know precisely what we mean when we use the
> constructors in the language to define a particular class of
> individuals.
>
> Turning back to an old example from KR, what does the following mean?
>
>    -------------             ---------
>    | telephone |--- colour ---| black |
>    -------------             ---------
>
> o Telephones are black?
> o All telephones are black?
> o Telephones can be black?
> o There is a telephone which is black?
>
> The crucial point with OWL is that we have a well-defined notion of
> what it means when we say:
>
> telephone -> all colour black
>
> i.e. all telephones can *only* have the colour black.

Well. Maybe we should use more astronomical examples :)

Anyway. I don't see why TM could not express that by using specific topics and
associations.

Define a topic representing the class "telephone"
Define a topic representing the concept "colour'
Define a topic representing the colour "black"
Define a topic representing the concept "class"
Define a topic representing the association type "class_colour"

Every one of the above being defined as a Published Subject if possible.

Then define an instance of the association-type "class_colour"
where "telephone" plays the role of "class" and "black" plays the role of "colour"

class_colour (class: "telephone" ; colour: "black")

And, at will, constrain the domain of validity of this assertion by a convenient scope,
like "1930, USSR" ;-)

Is there less semantics in the TM expression than in the OWL expression?
Let alone the capacity of the latter to draw inferences ...

Bernard

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Bernard Vatant
Consultant - Mondeca
www.mondeca.com
Chair - OASIS TM PubSubj Technical Committee
www.oasis-open.org/committees/tm-pubsubj/
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