Re: Closure Axiom and inferences issues
Gabriela Medina <[email protected]>
| Newsgroups | gmane.comp.misc.ontology.protege.general |
|---|---|
| Message-ID | <[email protected]> |
Hello Thimoty, Thanks for your answer. It's very clear! The realized that the problem that I had is that I didn't use the "closure axiom" for the instances to say that was the only thing they had. Actually I didn't know it was possible. Thanks for your help! It was very useful! Best regards, Gabriela ________________________________ De : Timothy Redmond <[email protected]> À : [email protected] Envoyé le : Lundi 2 juillet 2012 17h46 Objet : Re: [protege-discussion] Closure Axiom and inferences issues On 06/29/2012 05:51 AM, Gabriela Medina wrote: Thanks for your answer Timothy. My ontology is the classical Pizza example (is included as an example when you download Protégé). You can do the test by yourself by adding some instances at the Pizza level (Pizza class) with VegetarianTopping and you'll see that they are not re-classified after the inference. This inference worked for me. There are two issues that might have given you trouble. First of all, in order to deduce that a pizza is a vegetarian pizza, you need to know all the toppings of the pizza, not just some of them. Thus if I give the myPizza individual two toppings, I also need to add another statement asserting that these are the only two. The other issue is that VegetarianPizza is an inferred superclass of the VegetarianPizzaEquivalent1 pizza class. So my pizza individual classifies into VegetarianPizzaEquivalent1 (or 2) and is not shown in VegetarianPizza. The particular view in the attached screenshot only shows the direct inferred instances. Also you can do the same but instead of VegetarianToppings you can add other toppings such as Mozzarella and Tomato.... (they're supposed to be classified after inference as instances of the Margherita Pizza)... The problem with Margherita pizza is different. The original pizza ontology does not give an equivalent class for the Margherita pizza; there are no axioms that force an individual to belong to the Margherita pizza class. I made a screenshot showing this. If I change the ontology slightly so that the MarghertaPizza class is defined (see attached image) then I can generate inferences about individuals being in the Margherita class. -Timothy Thanks in advanced for your help! Gabriela > > >________________________________ > De : Timothy Redmond <[email protected]> >À : [email protected] >Envoyé le : Jeudi 28 juin 2012 15h17 >Objet : Re: [protege-discussion] Closure Axiom and inferences issues > > > > > >>Those instances are supposed to be a member of the "VegetarianPizzaEquivalent1" and "Margherita" classes after the inference process. Those classes use in their definition the Closure Axiom (i.e. ONLY). > >Conceptually your plan with the closure axiom should have worked and no sub properties should have been necessary. If you send the ontology I can perhaps have a look and see what went wrong. > >-Timothy > > >On 06/22/2012 07:19 AM, Gabriela Medina wrote: > > >> >>Hello, >> >> >>I've been recently using Protégé and I have one question. I have used the Pizza example to see how inferences performed by reasoners (Pellet, Hermit...) worked. In that sense, I have introduced instances of the "Pizza Class" to see how they were classified after the inference (I have mainly worked with Pellet but i have also used other reasoners). Those instances have the following characteristics: >>1. One of the instance has a Vegetarian Topping. >>2. Another of the instances has Mozarella and Tomato Topping. >> >> >> >>Those instances are supposed to be a member of the "VegetarianPizzaEquivalent1" and "Margherita" classes after the inference process. Those classes use in their definition the Closure Axiom (i.e. ONLY). However, when i performed the inference, those instances weren't classified as members of the "VegetarianPizzaEquivalent1" and "Margherita" classes. >> >> >>I have performed several tests to understand how reasoners worked and I have one possible explanation that i would like to confirm with you. Actually I think that when one use an Object Property with a large Range (for example in the Pizza example, the hasTopping property has as a Range the PizzaTopping class) and when one use the Closure Axiom for the definition of class, the reasoner suppose that the instances of the "defined class" could have the all the classes of the Range (i.e. all kind of Pizza Toppings) and NOT ONLY the specified classes precised for the Closure Axiom. In that sense, the definition of the Margherita Classprecised that this class "hasTopping ONLY (MozzarellaTopping or TomatoTopping)". However, hasTopping property has a very large Range which is "Pizza Topping. For this reason, inference is not performed. >> >>As a solution to this issue, I have created sub-ObjectProperties such as "hasToppingMargherita" with Domain "Margherita Pizza" Class and with Range "Tomato" and "Mozarella Toppings". This solution worked and instances were classified in their respective classes. Nevertheless I found this solution demands harder modeling efforts. Besides, in that case, it isn't worthy to use the Closure Axiom, since Range will be already limited in the SubProperty. >> >>What do you think about my explanation? and about my solution? any suggestion? >> >>Thanks in advanced for your reply and for your help, >>Kind regards, >>Gabriela >> >> >> >> >> >> >> >>_______________________________________________ protege-discussion mailing list [email protected] https://mailman.stanford.edu/mailman/listinfo/protege-discussion Instructions for unsubscribing: http://protege.stanford.edu/doc/faq.html#01a.03 > > >_______________________________________________ >protege-discussion mailing list >[email protected] >https://mailman.stanford.edu/mailman/listinfo/protege-discussion > >Instructions for unsubscribing: http://protege.stanford.edu/doc/faq.html#01a.03 > > > > > >_______________________________________________ protege-discussion mailing list [email protected] https://mailman.stanford.edu/mailman/listinfo/protege-discussion Instructions for unsubscribing: http://protege.stanford.edu/doc/faq.html#01a.03 _______________________________________________ protege-discussion mailing list [email protected] https://mailman.stanford.edu/mailman/listinfo/protege-discussion Instructions for unsubscribing: http://protege.stanford.edu/doc/faq.html#01a.03 _______________________________________________ protege-discussion mailing list [email protected] https://mailman.stanford.edu/mailman/listinfo/protege-discussion Instructions for unsubscribing: http://protege.stanford.edu/doc/faq.html#01a.03