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[protege-owl] Layered Ontologies?

Thomas Russ tar at ISI.EDU
Wed Mar 4 14:21:38 PST 2009

On Mar 3, 2009, at 11:00 AM, Pitonyak, Andrew D wrote:

> The constraints are required for OWL DL to fall into the domain of a  
> "Description Logic". In other words, people that study logic and  
> reasoners know that if you stay in OWL DL, then your reasoner is  
> able to make decisions (things are "decidable"). Examples include  
> things like: Is an instance a particular type, checking relations,  
> is a concept a subset of another concept, and is a concept  
> consistent. I expect that consistency is a real problem in OWL FULL.

Actually, I would think that completeness rather than consistency is  
the issue.

There is (or at least has been) more than one school of thought in the  
development of description logics.

The fundamental issue is that one has four useful characteristics of a  
reasoning and representation system that one would like to have  

  1.  Sound reasoning.
  2.  Complete reasoning.
  3.  Expressive language.
  4.  Efficient implementation.

But the problem is that you can't have all four.  You have to choose  
at least one of these items to restrict in order to get the other  
three.  The OWL language design chooses to sacrifice #3 so items 1, 2  
and (mostly) 4 can be realized.  Other systems in the past have made  
other design trade-offs.  One other popular choice was to sacrifice #2  
to emphasize 1, 3 and 4.  That happens to be the design school that I  
identify with.

But different applications have different needs, so a single choice is  
not always right for what you want to do.

Thomas A. Russ, Ph.D.  Senior Research Scientist             tar at
USC/Information Sciences Institute     
4676 Admiralty Way, Marina del Rey, CA 90292              (310) 448-8775

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