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

[lisa colvin]

Hi Nuno!

> So basically unless the study of
> Ontologies brings new
> modeling artifacts that OOA does not have on its
> nature it may well be that it does not bring
anything new 
> from the engineering point of view.

Correct. Most of the current research in ontologies
has been on the more practical side: correctly
integrating multiple ontologies; developing logical
principles for ontology creation to prevent “semantic
drift”, and the challenges of using ontologies in
applications.

> Or probably a multidisciplinary effort could bring
some light on this theme.

Definitely. “Ontology” is term that gets thrown around
to describe any number of things, which is confusing.
Ironically, part of the purpose of having an ontology
is to have a common language ;)

> Individuals are
> instances of a Class
> right? So if they are in OOA they are called Class
> Instances (also Objects) not individuals. 

Sorry! Sloppy of me. I meant “instances”, not
individuals. I’m not sure if instantiation works the
same.

> Instances exists not
> only for Classes in OOA but also Associations (Slots
> of type Instance)
> in this case OOA calls these type of instances
Links.

This may be an area of differentiation. I can’t speak
for all systems, but the ones I worked on didn’t have
instances of predicates. It really didn't make sense
in our system as predicates can take any class or
instance of a class as arguments.

 
> So can in OOA. Actually multiple inheritance (a
> class having multiple
> super classes) in a practical point of view was
> abandoned. It was found
> that it does not actually map the perceived reality
> that well and
> creates "feature" overlap. Instead other patterns
> were discovered that
> can map the world more faithfully.
> 

Multiple inheritance is alive and well in ontology
development! It is considered a key and necessary
feature. There is a tradeoff between ease of
development/consistency and redundancy.  What other
“patterns” are you speaking of? 

> >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.
> 
> Very interesting indeed. I'm not sure if I fully
> understand thought. Do
> predicates exist without classes? If no, then a
> predicate must be
> related to at least one class right, this
> considering that predicates can be unary (The Root
Class)? 

Exactly! 

> Sub classes my restrict the "predicate"
> (association) but restrictions can only be made
> along the set of sub classes of that Root class. 

What I was thinking was this :

Define: DRINK 
(isa DRINK BinaryPredicate)
	 (arg1Isa DRINK SentientBeing)
	(arg2Isa DRINK PotableObject)

So what this says is that the 1st argument to DRINK
must be an instance of the SentientBeing class (or its
subclasses) and the 2nd argument must be an instance
of the Potable Object class. This is written in
pseudo-cycl.

This is useful for many things, including metaphoric
understandings (which I used to work on)…In this case,
we know that the second argument to DRINK must be a
PotableObject so if I say “I drank the glass” then it
is unacceptable, but there may be some
reinterpretation rules that could remap containers to
the objects they contain if there is a constraint type
violation. But I digress… ;)


If so in OOA the same
> can be defined easily.
> As I remember Prolog we could make question over
> predicates too. Most OO

In CycL, for instance, there is quantification over
logical statements. It’s true that performance is
hindered by such flexibility which is why Cyc has a
bunch of optimizations on popular predicates operating
in the inference engine.

> Hum I understand. But to be honest the state of the
> art sample about
> wines provided in the articles do not use that
> feature. I would like to discuss the reasons of this
fact.

I don’t think the wine examples are state-of-the-art.
I think the purpose of the wine example is to show
multiple inheritance along a faceted hierarchy which
is only one end of the spectrum of ontology
development.

> Can you provide me
> with some links and point to me what you think is
> relevant in the light of my statements? 

Nicola Guarino is the best source for the logical
underpinnings of ontology development. He’s quoted the
most. Some of the reading is a bit dense, so not for
bedside! ;)
http://ontology.ip.rm.cnr.it/Publications.html

Thanks for this conversation, Nuno. It’s very helpful.

;)lisa



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