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From Ian Dickinson <>
Subject Re: symmetry of class-equivalence relation in OWL
Date Tue, 21 Dec 2010 09:13:23 GMT
Hi Sean,
On 21/12/10 08:30, Chris Dollin wrote:
> On Tuesday, December 21, 2010 06:21:21 am Sean Champ wrote:
>> Hi folks, just a question:
>> Given an OWL class A, with A denoted as (the subject) having an equivalent
>> class B: I've seen that Jena will return B within the return value of
>> A.listEquivalentClasses(). However - in my experience with using Jena 2.6.3
>> - the return value of B.listEquivalentClasses() will not contain A, in that
>> same situation.
> What reasoner are you using?
> The different OntModelSpec's give you different reasoning power. The
> /default/ reasoner for createOntologyModel only does RDFS reasoning,
> which knows not owl:equivalentClass.
> So show us how you create your model.

Just to follow-up on what Chris wrote with a brief explanation: the 
convenience methods in the Ontology API, such as 
listEquivalentClasses(), are designed to work on whatever triples it the 
OntModel can see - those methods don't do any computation themselves. 
Jena's layered architecture means that if you use a reasoner, it will 
/appear/ as though additional triples are in the model, when in fact 
they're entailed from the triples asserted in the base model. So with 
listEquivalentClasses as an example, the symmetry of the 
owl:equivalentClass relationship entails

:B owl:equivalentClass :A


:A owl:equivalentClass :B

But this has to be handled by a reasoner that can process the semantics 
of OWL. As Chris wrote, the default model, for historical reasons, 
handles only the semantics of RDFS. If you create your OntModel with (wteo):

OntModel m = ModelFactory.createOntologyModel( 

you should see the symmetry you're expecting.


Ian Dickinson                   Epimorphics Ltd, Bristol, UK
cell: +44-7786-850536              landline: +44-1275-399069
Epimorphics Ltd.  is a limited company registered in England
(no. 7016688). Registered address: Court Lodge, 105 High St,
               Portishead, Bristol BS20 6PT, UK

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