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Re: ISSUE: Classes as instances

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 17 Jul 2002 10:31:09 -0400
To: schreiber@swi.psy.uva.nl
Cc: www-webont-wg@w3.org
Message-Id: <20020717103109Y.pfps@research.bell-labs.com>

From: Guus Schreiber <schreiber@swi.psy.uva.nl>
Subject: Re: ISSUE: Classes as instances
Date: Wed, 17 Jul 2002 15:59:23 +0200

> Peter F. Patel-Schneider wrote:
> > From: Guus Schreiber <schreiber@swi.psy.uva.nl>
> > Subject: Re: ISSUE: Classes as instances
> > Date: Fri, 12 Jul 2002 15:12:46 +0200

[...]

> >>One could
> >>therefore argue that this representation is wrong. 
> > 
> > Please explain.  What is ``wrong'' about this representation?
> 
> I did not say it was (I actually think it's fine). See previous point.
> However, I am not sure you would be happy with it, as it implies that 
> WordNet synsets such as denoted by the terms "animal" and "human" are 
> represnted as RDF/OWL individuals.

I'm not unhappy with representing the wordnet hyponym relationship as an
uninterpreted property at all.  Depending on what one wants to do, it may
be the best way of representing this relationship.

[...]

> >>The tool uses the
> >>hierarchy in several ways. e.g.:
> >>- for making it easy for users to understand the intended
> >>  meaning of a term (e.g. "Venus" as a subclass of "Roman deity" or as a
> >>  subclass of "planet"). This is used in annotation/search term
> >>  disambiguation.
> >>- for query generalization/specialization.
> >>[See [3] for more info]
> > 
> > Why does the tool depend on subclass?  Would it not be just as easy
> > to use a transitive relationship?
> 
> I think many RDF (and OWL) tools and applications will be treating the 
> subclass relation in a special way. What is wrong with that?

Well the subclass relation *is* special, so it should be treated in a
special way.  However, making tools that can only use the subclass
property for retrieval, etc., is not a good idea, as it prevents other
properties from being used for retrieval.  For example, suppose there was
another large KB that had a transitive property that one would want to
query but that this property was not related to the subclass property.  How
would your tool handle this?   Should OWL have to support tools that are
limited in this way?

[...]

> >>3. Implications for OWL
> >>
> >>OWL should not disallow this type of mapping.
> > 
> > 
> > I don't think that you have provided convincing evidence of this
> > conclusion.
> > 
> 
> I disagree. I think it is a realistic example of how things will (need 
> to) work in practice.
> 
> Every time I present an ontology-representation or -mapping problem, the 
> standard answer from some seems to be that either the representation or 
> the mapping is wrong. But what are you going to do: install a higher SW 
> authority to enforce "correct" mappings and representations?

No, of course not.   I'm not saying that what you did was wrong.  I am,
however, saying that I don't see a justification for classes as instances
in what you did, because all that it appears that you did was to use the
transitivity of subclass.  

In essence, you encoded hyponymOf as subClass.  There is nothing wrong with
encoding, but it is not representation, and I don't think that a use of
encoding should be used to justify elevating that use into a representation
language.

> I am afraid that in this way we will not be building a semantic web, but 
> a set of semantic islands with high fences surrounding them....

I am afraid that other ways will lead to buiding a semantic swamp, filled with
quicksand and alligators.


peter
Received on Wednesday, 17 July 2002 10:31:19 GMT

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