[Pellet-users] Inferred Subsumption
JPQ
jpq.semantics at gmail.com
Fri Mar 7 20:14:19 UTC 2008
Oops... one adjustment. Per the OWL specs <owl:Restriction> is a subclass of
<owl:Class>. A property restriction, therefore, is wrapped in an anonymous
class described by <owl:Restriction>. As before, this can be shown in the
"Diagram" view of TopBraid Composer. A gray box containing the property
restriction signifies the anonymous class defined by the <owl:Restriction>
language construct.
On 3/7/08, JPQ <jpq.semantics at gmail.com> wrote:
>
> Evren,
>
> Thanks for the reply; it sheds new light on my understanding of OWL.
>
> Basically, OWL describes classes in one of two ways:
>
> 1. A named (ie, Type-1) class, which is formed from the <owl:Class>
> construct, including a URI reference
> 2. An unnamed (ie, anonymous) class, which is formed from the
> <owl:Class> construct and lacks a URI reference
>
> As for class descriptions:
>
> 1. A class identifier is defined by point 1 above
> 2. An enumeration contains a list of invidividuals. Lacking other
> class description types, a class (named or anonymous) having an enumeration
> class description means its class extension has EXACTLY those individuals
> and no others.
> 3. A property restriction defines value and cardinality constraints.
> Lacking other class description types, a class (named or anonymous) having
> property restrictions means its class extension must adhere to the value and
> cardinality "rules" described by the restrictions, and these "rules" are
> local to the class.
> 4. Class descriptions 4-6 (the set operations) limit the selection
> of individuals from other classes described in the set operations. Lacking
> other class description types, a class (named or anonymous) utilizing set
> operations means its class extension is EXACTLY described by individuals of
> other classes that meet the criteria of the set operations.
>
> If this is an accurate description, then it is clear that class
> equivalency can ONLY be established through the <owl:equivalentClass>
> construct. In fact, this can be demonstrated in TopBraid Composer with the
> following example.
>
> 1. Create a named class, and define a union set operation only.
> 2. Select the class in the "Classes" pane, and then switch over to
> the "Diagram" view. The union operation does not displayed, because it does
> not signify a class.
> 3. Modify the named class as follows.
> 1. Wrap the union operation in an anonymous class
> 2. Wrap the anonymous in <owl:equivalentClass>
> 4. Save the file
> 5. Select the named class in the "Classes" pane; switch to the
> "Diagram" view. The union operation is not displayed inside a gray box. The
> gray box signifies an anonymous class. There is an equivalency relation (ie,
> a thick double-head black arrow) drawn between the anonymous class (ie, the
> gray box) and the named class.
>
>
> On 3/6/08, Evren Sirin <evren at clarkparsia.com> wrote:
>
> > [Note: please send Pellet questions to the mailing list not privately]
> >
> > On 3/5/08 2:26 PM, JPQ wrote:
> > > As a follow-up to my last post, a recent discussion elsewhere
> > suggested that
> > > Pellet does not return inferences on blank nodes. This would explain
> > why
> > > Pellet infers a subsumption and not an equivalency. More specifically,
> > here
> > > is what Pellet returns in Topbraid Composer.
> > >
> > > Another_Ontology:Lat rdfs:subClassOf LatLon
> > > Another_Ontology:Lon rdfs:subClassOf LatLon
> > >
> > > I accepted to see the following inference, also.
> > >
> > > LatLon rdfs:subClassOf
> > > [Another_Ontology:Lat or Another_Ontology:Lon]
> > >
> > > These inferences collectively describe the equivalency between
> > "LatLon" and
> > > "[Another_Ontology:Lat or Another_Ontology:Lon]".
> > >
> >
> > In you snippet there is no blank node that describes the union class. If
> > your definition was written as follows (using an anonymous class for the
> > union description):
> >
> > <owl:Class rdf:ID="LatLon">
> > <owl:equivalentClass>
> > <owl:Class>
> > <owl:unionOf rdf:parseType="Collection">
> > <rdf:Description rdf:about="Another_Ontology.owl#Lat"/>
> > <rdf:Description rdf:about="Another_Ontology.owl#Lon"/>
> > </owl:unionOf>
> > </owl:Class>
> > </owl:equivalentClass>
> > </owl:Class>
> >
> > then you would get a bnode in the inferences (but Jena will not pretty
> > print the bnode in the Manchester syntax you have above). Also note that
> > Pellet will only return asserted relations regarding bnodes. See this
> > FAQ entry for more information [1].
> >
> > If you are interested in seeing why the subclass relation holds then you
> > can take a look at the explanation feature Pellet provide. Pellet will
> > give you the set of asserted axioms for a given inference. See the
> > explanation example program from Pellet distribution.
> >
> > Cheers,
> > Evren
> >
> > [1] http://pellet.owldl.com/faq/different-results/
> >
> >
> > > On 3/4/08, JPQ <jpq.semantics at gmail.com> wrote:
> > >
> > >> Thanks for your reply.
> > >>
> > >> Let me phrase it a bit differently.
> > >>
> > >> First, we have the following OWL class, which is contained within an
> > >> OWL-DL ontology. In fact this ontology only contains this one class
> > and no
> > >> properties. Additionally, it imports a second ontology, which I have
> > called
> > >> "Another_Ontology".
> > >>
> > >> <owl:Class rdf:ID="LatLon">
> > >> <owl:unionOf rdf:parseType="Collection">
> > >> <rdf:Description rdf:about="Another_Ontology.owl#Lat"/>
> > >> <rdf:Description rdf:about="Another_Ontology.owl#Lon"/>
> > >> </owl:unionOf>
> > >> </owl:Class>
> > >> The named OWL class, "LatLon", is equivalent to the nested anonymous
> > class
> > >> that is formed by the "unionOf" set operator. For example, suppose
> > the class
> > >> extension of "Lat" is represent by the set {1, 2, 3}, and the class
> > >> extension of "Lon" is represented by the set {4, 5, 6}. Then the
> > class
> > >> extension of "LatLon" is exactly the same as the union of those two
> > sets -
> > >> namely, {1,, 2, 3, 4, 5, 6}.
> > >>
> > >> Yet, when run through Pellet, it is inferred that
> > >> "Another_Ontology.owl#Lat" & "Another_Ontology.owl#Lon" are
> > subclasses of
> > >> "LatLon".
> > >>
> > >> My question is what is the basis of these inferences?
> > >>
> > >> Thanks.
> > >>
> > >> On 3/4/08, Evren Sirin <evren at clarkparsia.com> wrote:
> > >>
> > >>> On 3/4/08 11:51 AM, JPQ wrote:
> > >>>
> > >>>> I'm running the Pellet inferencing engine in TopBraid Composer on a
> > >>>>
> > >>> valid
> > >>>
> > >>>> OWL-DL document. Here are the details.
> > >>>>
> > >>>> An OWL-DL ontology contains the following class.
> > >>>> <owl:Class rdf:ID="LatLon">
> > >>>> <owl:unionOf rdf:parseType="Collection">
> > >>>> <rdf:Description rdf:about="Another_Ontology.owl#Lat"/>
> > >>>> <rdf:Description rdf:about="Another_Ontology.owl#Lon"/>
> > >>>> </owl:unionOf>
> > >>>> </owl:Class>
> > >>>>
> > >>>> The anonymous class formed by the "unionOf" set operation is
> > >>>>
> > >>> equivalent to
> > >>>
> > >>>> the named class, "LatLon".
> > >>>>
> > >>>> This ontology imports a second ontology.
> > >>>>
> > >>>> The second OWL-DL ontology ("Another_Ontology") has the following
> > >>>>
> > >>> features:
> > >>>
> > >>>> 1. The "Lat" & "Lon" classes are Type-1 OWL classes (ie, they are
> > >>>>
> > >>> simply
> > >>>
> > >>>> identified as RDF nodes using the rdf:ID construct)
> > >>>> 2. There exist "lat" & "lon" datatype properties
> > >>>> a. The "lat" property domain is "Lat"; its range is
> > "xsd:double".
> > >>>>
> > >>> The
> > >>>
> > >>>> same applies with "lon",
> > >>>> except its domain is "Lon".
> > >>>> (I've also tried an alternate version where the "lat" &
> > "lon"
> > >>>> datatype properties only define
> > >>>> ranges and not domains.)
> > >>>>
> > >>>> b. Both the "lat" & "lon" datatype properties are also typed
> > with
> > >>>> <owl:FunctionalProperty>
> > >>>>
> > >>>> Running the Pellet inference engine on the first ontology results
> > in
> > >>>>
> > >>> the
> > >>>
> > >>>> following inferences.
> > >>>> Another_Ontology:Lat rdfs:subClassOf LatLon
> > >>>> Another_Ontology:Lon rdfs:subClassOf LatLon
> > >>>>
> > >>>> The "LatLon" class subsumes "Lat" & "Lon".
> > >>>>
> > >>>>
> > >>> Ok, everything sounds right until now.
> > >>>
> > >>>
> > >>>> Why does Pellet infer these subsumptions when the "LatLon" class
> > >>>>
> > >>> description
> > >>>
> > >>>> defines an equivalency?
> > >>>>
> > >>>>
> > >>> I don't understand the question or the problem. Are you saying that
> > the
> > >>> subclass relations do not hold when you change the definition of
> > LatLon?
> > >>> If so, what is the changed definition? Providing complete, minimal
> > >>> ontologies would help us understand what is wron.
> > >>>
> > >>> Cheers,
> > >>> Evren
> > >>>
> > >>>> Thanks for your help.
> > >>>>
> > >>>>
> > >>>>
> > >>>>
> > >>>
> > ------------------------------------------------------------------------
> > >>>
> > >>>> _______________________________________________
> > >>>> Pellet-users mailing list
> > >>>> Pellet-users at lists.owldl.com
> > >>>> http://lists.owldl.com/mailman/listinfo/pellet-users
> > >>>> _______________________________________________
> > >>>>
> > >>>> Sponsored by Clark & Parsia, LLC http://clarkparsia.com/
> > >>>>
> > >>>
> > >
> > >
> >
> > _______________________________________________
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> >
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> >
>
>
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