[Sigia-l] CMS and IA-Ontologies vs. Data Modelling

[lisa colvin]

Hi Nuno,

Great discussion.

--- Nuno Lopes <nbplopes at netcabo.pt> wrote:

>In other words, most of the topics being addressed I
see equivalences
>with Relational Modeling and OOA at some point (even
between them). 
>With
>leads me to suspect that probably they don't solve
much more then what
>we already have mainstream (RDBMS, OODMS, etc) from
the point of view 
<of
<engineering.

Modelling is modelling so from that perspective many
of the issues are transparent along the different
disciplines. I think the problems in a generic sense
(interoperability) are similar. Most of the power of
having an ontology, however, is in coupling it with a
logical inferencing engine and have the data is
represented in an RDBMS.

>This leads me to the next question, what is the main
difference >between
>"Ontology" and an Object Oriented Data Model defined
in UML for
>instance? 

An ontology is a model. UML is a modeling language.
Similarly, ontologies are expressed in different
ontology languages, varying in expressivity.

>Are the so called Slots not more then Class
attributes? Is it that in 
>classical OODM we can extend or restrict Class
attributes and Classes 
>in
>the scope of Ontologism we may only restrict the
possible values of
> Slots in the sub classes?

The term “slots” is a carryover from frame systems.
Sometimes you may hear the word “predicate” to mean
the relationship between two classes or individuals
(of a class). A predicate is an n-nary relationship
between classes and individuals. You can define a
predicate to exist between 2 classes, for example or
between a class and an individual or multiple
individuals. Further, in more complex systems, you can
also define the mathematical relationships (e.g.
transitivity) for that particular predicate.
Similarly, some predicates could have predicates
themselves as arguments.

So you are not just restricting values, but also
potentially the type of classes that can be arguments
to that predicate. These “type” restrictions are very
helpful in many applications, like natural language
processing.

>Within this
>scope aren't these Sub Classes nothing more then
information views >over
>the extent of a more generic OODM that merely define
common abstract
>properties without fixing values for attributes for
each class (Class
>Wine only)? 

The scope of subclasses is a bit different than the
database views. Sometimes the information on lower
nodes is an expansion rather than a contraction of
higher nodes. Because an ontology is a graph rather
than a tree, the lower nodes may be inheriting
information from other parents.

Hope that’s helpful. It’s difficult to have knowledge
sharing when our descriptions of knowledge are so
different!

:)lisa
<p.s. disclaimer: my background is as an
ontologist/linguist from research (cyc) to software
design…so that's my bias ;)>



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