[topicmapmail] RE: back to the lists

[Murray Altheim]

Bernard Vatant wrote:
> Martin
> 
> Note that I wrote :
> 
> " Expressivity of OWL is flexible enough to express a *wide variety* of
> TM constraints."
> 
> And you answer :
> 
> " I don't see this as being helpful in describing *all of the
> constraints* TMCL is supposed to provide."
> 
> I don't know what "all of the constrains" means, and a big issue indeed
> is to define the limits of TMCL. That's why I said *a wide variety*.
> 
> The example you give is maybe borderline one ...
[...]

I have a few examples that are not borderline.

While one of the things the Topic Map community has not yet
produced is a framework for ontologies, such as might be
provided by some translation of first order logic, modal
logics, description logics, Conceptual Graphs, or some other
foundation of a knowledge representation system, this isn't
for lack of ability in the design of topic maps (since Topic
Maps would simply serve as a graph basis, as does RDF in OWL).
It's just that nobody has tackled it. We're a small community,
and all overbooked.

But one of the things Topic Maps even in their basic functionality
do support is *context*. My understanding is that OWL does not
currently support contexts. I'm not sure if this is due to its
basis in RDF, issues of reification, whatever. But a system that
can't manage various contexts will make comparative analysis,
merging of multiple ontologies from different sources, and many
other important knowledge representation issues impossible to
constrain in a constraint language.

The example in the OWL guide [1] states that OWL cannot currently
support implication, modality, or context:

   Implication:   IF a THEN b
   Modality:      EVENTUALLY, ALWAYS
   Contextuality: "The book states that the earth is 6000 years old"

Something like CG can support the first two, and I believe context
as well. The current work on Common Logic (CL) will IMO likely
yield a more workable framework for at least my own purposes. With
Topic Map's use of scope, it has the ability to express context at
a number of levels.

I think it folly to pretend that the world or KR/ontologies can be
represented in one description logic-based syntax. The field is
too wide, there are too many domains with too many different
requirements.

Murray

[1] http://www.w3.org/2001/sw/WebOnt/webont-issues.html#I5.4-OWL-QUOTE
......................................................................
Murray Altheim                  <http://kmi.open.ac.uk/people/murray/>
Knowledge Media Institute
The Open University, Milton Keynes, Bucks, MK7 6AA, UK

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