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[protege-owl] Transitivity isn't working!! Why?

Bram Gadeyne gadeynebram at gmail.com
Wed Nov 3 07:23:15 PDT 2010


Hi all,

I'm also using the transitivity relation with protege owl 3.4.

But the log of Pellet indicates that it ignores the transitivity relation
because of a cardinality restriction on the object property.

I did not indicate this restriction in with the property itself. The only
things I can find are within the necessary and sufficient blok of some
classes where I state the following:

1) isPeriodPartOf only abstract_period (with isPeriodPartOf beiing defined
as a transitive property.)
2) hasPeriodParts min 2 (with hasPeriodParts beiing the inverse of
isPeriodPartOf and also transitive.)

But I would think that such a restriction in a necessary and sufficient
block would not generate such a warning in pellet since it is not a global
cardinality restriction.

With kind regards
Bram Gadeyne



2010/11/1 Timothy Redmond <tredmond at stanford.edu>

>
> In Protege 4, these inferences are easily seen (more below).  I think that
> the problems you are having are:
>
>    1. Protege 3 does not seem to show these types of inferences.
>    2. SPARQL doesn't understand OWL semantics and can't be expected to
>    infer things about transitive properties.  There is SPARQL-DL capability
>    which is supported by pellet but I don't know of a Protege plugin providing
>    a ui for accessing these capabilities.
>
> In the latest Protege 4.1, the following will show these inferences:
>
>    1. If you haven't changed your reasoning preferences, this step is not
>    needed.  Click Reasoner->Configure and ensure that "Object Property
>    Assertions" is selected near the bottom of the displayed inferences tab.
>    2. In the reasoner menu, choose a reasoner (HermiT should be there
>    after a fresh install) and then click Reasoner->Start Reasoner.
>    3. Go to the individuals tab, select the Class People and then select
>    the user Alice.  You will see a highlighted property towards the right,
>    indicating that Carol is senior_to Alice.  This property value was put there
>    by the reasoner.
>
> You can also do other more complicated queries in the DLQuery tab (which
> also uses the reasoner).  For example if you put
>
>  senior_to value Carol
>
>
> in the Query widget, select Individuals and click "Execute" you will see
> that the reasoner knows that both Bob and Alice are senior to Carol.  You
> can make many different types of queries here.  In particular, you could ask
> who is junior to Alice with the query
>
>  inverse(senior_to) value Alice
>
>
> More information on the expressions that you can enter in the DLQuery tab
> can be found here [1].
>
> -Timothy
>
> [1] http://www.co-ode.org/resources/reference/manchester_syntax/
>
>
> On 11/01/2010 01:58 PM, Alex Macfie wrote:
>
> I am defining an OWL ontology that extensively uses transitive
> properties. However, I  find that no reasoner infers any transitive
> relations. I would naturally expect, if I define property senior_to as
> transitive, and assert the following:
>
> Individuals: Alice, Bob, Carol
> Alice senior_to Bob
> Bob senior_to Carol
>
>  I expect to be able to infer through the transitive senior_to
> relationship that
> Alice senior_to Carol
> Yet the Pellet reasoner does not add any new relationships, and SPARQL
> only lists the direct relationships when I do a query like
> SELECT ?subject ?object
> WHERE { ?subject :senior_to ?object }
>
> What is going on here? What is the point of the "transitive" tick-box
> when creating a property if it cannot be used to actually infer
> transitive relationships? I am fairly new to OWL and Protege but I know
> what transitivity is and what one would expect to infer with a
> transitive property. So I find it very frustrating that this elementary
> concept doesn't actually seem to *work*.
>
> Regards
>
> Alex
>
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-- 
Bram Gadeyne
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