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Re: [OWLWG-COMMENT] ISSUE-55 (owl:class)

From: Jim Hendler <hendler@cs.rpi.edu>
Date: Mon, 10 Dec 2007 21:23:40 -0500
Message-Id: <D00E6C40-64FA-402E-ABFC-0805D19AB703@cs.rpi.edu>
Cc: Michael Schneider <schneid@fzi.de>, "Owl Dev" <public-owl-dev@w3.org>, <boris.motik@comlab.ox.ac.uk>, <pfps@research.bell-labs.com>, <ian.horrocks@comlab.ox.ac.uk>, <dlm@ksl.stanford.edu>, <hans.teijgeler@quicknet.nl>
To: Alan Ruttenberg <alanruttenberg@gmail.com>
hmm,  I think I do know the difference between an RDFS ontology and  
an OWL ontology in usage.  If I am a user who comes from an RDF  
perspective or is not convinced of the value of OWL, I use a tool  
(usually a reasoner done procedurally) for RDFS.  I am happy, my  
stuff works, and I use rdfs:class.  I write webapps using Sparql, I  
create very large triple stores, I create a Web 3.0 startup and make  
money.  I know some day it might be worth looking at OWL, but right  
now, I have no reason to - what it adds is not worth the extra work  
of converting things.
  On the other hand, I could be a user who has come into things from  
AI (like most of the people on the cc of this message).  I'm  
convinced OWL is a good thing, and I use owl:class (and maybe even  
make my ontology expressive).  When I create Aboxes to go with my  
ontology, I do them in RDF, and things seem to work okay.  I tend not  
to use huge triple stores, and I tend to use a single ontology at a  
time.  I work for a drug company or doing some "intranet" data  
integration.  I like OWL DL. I also make money.
  So basically, we have two different groups who end up coming at  
things from different directions and not meeting in the middle.  I'd  
love to see a fix, but I also understand the worldview that cannot  
live with this.
  but I'll tell you this based on experience and analysis of lots of  
stuff out there - telling people that the "right thing" to do is to  
use owl:class won't change much, because the people using rdfs:class  
to start with generally aren't coming from an OWL perspective, and  
therefore don't see a reason to change.
   So I see that if there was a solution in resolving these, we would  
make it easier for people to come to OWL - on the other hand, they're  
probably using inverseFunctional datatypes (the most commonly used  
construct we found in the RDFS and OWL Full documents) so it may not  
matter...
  JH
p.s. finding a way to reconcile the two worldviews seems  to be  
pretty much opposite the direction we're going w/OWL 1.1 - so maybe  
the "multi stack" solution is the best we can hope for.


On Dec 10, 2007, at 1:23 PM, Alan Ruttenberg wrote:

> Here's my understanding of the situation (if I've got it wrong  
> somewhere, please correct me).
>
> On Dec 8, 2007, at 3:20 PM, Michael Schneider wrote:
>
>> But, AFAICS, this would only become a real problem, if in this  
>> ontology some class is used as an individual (metamodelling).
>
> Or if the class has instances that are literals.
>
>> But in such a case, even after changing rdfs:Class to owl:Class,  
>> the resulting ontology would still be an OWL-Full ontology: There  
>> would, for example, be an 'rdf:type' triple with some class being  
>> at the individual position, or a class with an object or data  
>> property
>> attached.
>
> The type triple is inferred in OWL Full - it doesn't have to be  
> explicit.
>
>> The OWL-DL reasoner would refuse to work in such a situation, of  
>> course.
>
> Because the triple would sometimes need to be inferred by the  
> reasoner itself, the DL reasoner can't detect the situation in all  
> cases. Strictly speaking, it can only detect the case where it  
> certainly shouldn't work.
>
>> So it looks to me that this recommendation is safe.
>
> I would say, no. However it might be ok if the user was warned, or  
> made an explicit declaration to that effect.
>
>> Or to summarize these recommendations in a simple rule of thumb:  
>> Assume 'rdfs:Class' in RDFS ontologies, assume 'owl:Class' in OWL  
>> ontologies.
>
> How do you tell the difference between and RDFS ontology and and  
> OWL ontology?
>
> I think what might "work" is commonly called "duck typing", as in,  
> if it walks like a duck and quacks like a duck, then....
>
> The application in this case would be to look for an *explicit*  
> mention of something that might be only *inferred* in an OWL Full  
> ontology. Absent the explicit mention, you might assume that that  
> the author did not intend there for such statements to be inferred  
> either. This would be a change from the current semantics, and  
> possibly a reasonable ones, depending, IMO, on how the OWL Full  
> advocates voted.
>
> -Alan
>

"If we knew what we were doing, it wouldn't be called research, would  
it?." - Albert Einstein

Prof James Hendler				http://www.cs.rpi.edu/~hendler
Tetherless World Constellation Chair
Computer Science Dept
Rensselaer Polytechnic Institute, Troy NY 12180
Received on Tuesday, 11 December 2007 02:23:46 GMT

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