Thanks Scott! Thanks for hanging in there. Two points. A. The hasValue rules do not contain the restriction part, so it could be applied to a named class.
B. it is possible in TBC to give classes properties such as hasPrice and a value for hasPrice. Which seems ok from the perpective that classes can have properties. But I think such modeling is a mistake since it will result in things like Limes being oranges. Given that RL rule. Best wishes, LFJ On Fri, Aug 26, 2011 at 2:47 PM, Scott Henninger <[email protected] > wrote: > <<But it does not seem reasonable to assert that a lime is an orange > simply because it has the same price as an orange. > >> > > No, it's entirely consistent with the model. I purposefully created the > example to show that the logical relationships created by the restriction > are what matters, not the name. > > <<What would happen is the model contains 'Lime is distinct from Orange". > This would create an inconsistency...no?>> > > Yes, if you had the assertion {:Lime owl:disjointClass :Orange} then there > would be an inconsistency since :alime is a member of both. > > You can also specify a cardinality restriction that there can only be one > price. This doesn't result in an inconsistency, but a SPIN constraint can > easily be created that checks for multiple prices. > > <<Also, the practice of attaching a property and a value restriction to a > class might make sense from an OO perspective, but it seems incorrect from a > modeling perspective. In fact, this is listed among the "Anti- patterns" in > Dean's book.>> > > I think I understand the misunderstanding. The anti-pattern, I'm guessing, > is the expectation that a property defined on a class is automatically > copied to (sometimes incorrectly called "inherited by") the instance. This > is an entirely different topic from what I stated - please note the careful > placement of the term "akin" in my statement below. > > First, let's be clear about the semantics of hasValue. A hasValue > restriction on a property means that in a consistent model all members of > the class (yes, the unnamed restriction class) have that property-value > (e.g. :hasPrice ".25"^^xsd:float). This is often referred to as > "entailment" - the restriction entails that all members of the class have > this property-value pair. If an instance does not, then the model is > inconsistent, and the reasoner will add the property-value pair to the > instance to make it consistent. > > The semantics of hasValue also states that if any resource matches the > property-value pair, then it is a member of the class. This is where the > fact that "the class" is the restriction class becomes important. The > inference occurs for the restriction class always. But if the restriction > is a subclass of the named class, then we can't infer that the instance is a > member of that class - members of the class may not be members of the > subclass. If the restriction is on an equivalent class property, then we > can make the inference on the named class since the members of the unnamed > restriction class and the named class are the same. > > I believe the OWL spec does not allow for named classes for defining the > restrictions. > > -- Scott > > On 8/25/11 5:59 PM, Leonard Jacuzzo wrote: > > Thanks Scott, > > But it does not seem reasonable to assert that a lime is an orange simply > because it has the same price as an orange. > What would happen is the model contains 'Lime is distinct from Orange". > This would create an inconsistency...no? > > Also, the practice of attaching a property and a value restriction to a > class might make sense from an OO perspective, but it seems incorrect from a > modeling perspective. In fact, this is listed among the "Anti- patterns" in > Dean's book. > > As another question regarding rules. > > Let's say that I avoid this OO pattern and instead define Orange as a > sublcass of a restriction on the property hasPrice to the value 25 cents. > (because that is better and true and would not result in anything having the > same price as an orange being classified as an orange).... > > How would a rule look that produces the fact that an individual orange(u) > hasPrice 25 cents?. > So what I would have something like > > Orange rdfs:subClassOf owl:restriction > owl:onProperty 'hasPrice' > owl: hasValue "..25" xsdfloat. > And > OrangeB rdf:type Orange. > > How do I go from there to > > OrangeB hasPrice value '.25' xsdfloat. > > Sorry for the sloppy fake code..I am a neophyte. > Thanks again for your help. I have learned a great deal. > > Best, > LFJ > > > So this rule is not truth preserving...in itself. It would only be truth > preserving with the appropriate "distinct' values. > On Thu, Aug 25, 2011 at 6:24 PM, Scott Henninger < > [email protected]> wrote: > >> Hello Leonard; Yes I do believe this is a typo in the rule set. We >> will look into this some more and get it fixed for the 3.6 release. >> >> The two rules, cls-hv1 and cls-hv2, are converses of each other. cls- >> hv1 covers the case where if a class defines a hasValue restriction >> property, then all members of the class must have that property >> value. The rule infers this, in typical OWA fashion, making the model >> consistent. So given a [:hasPrice value ".25"^^xsd:float] restriction >> on :Orange, the triple {?u :hasPrice ".25"^^xsd:float} is inferred for >> all members of Orange. Note that members of :Orange can also have >> other :hasPrice values - e.g. {?u :hasPrice ".50"^^xsd:float} - and >> that is consistent with the model. >> >> The cls-hv2 covers the case that if a resource meets the hasValue >> criteria, then it is a member of the class. So let's say we have an >> instance with the triple {:alime a :Lime ; :hasPrice ". >> 25"^^xsd:float}, since the value of :hasPrice is .25, it meets the >> criteria of :Orange membership and therefore the rule infers {:alime >> a :Orange}. The tricky part to understand in this query is that ?u >> refers to any resource. In our example the graph pattern is matched >> as: >> WHERE >> { ?x owl:hasValue ?y . ## ?x bound to bnode representing the >> restriction, ?y bound to ".25" >> ?x owl:onProperty ?p . ## ?p bound to :hasPrice >> ?u ?p ?y . ## ?u bound to : alime >> } >> >> Try this in your SPARQL view by applying the above to a model that has >> some hasValue restrictions. I'd suggest using 'SELECT *' so you can >> follow the variable mappings. >> >> <<BTW: what does it mean to assert that a class X hasValue y on >> property P? >> The class Orange does not have a price, only individual oranges have a >> price.>> >> >> If you are familiar with OO programming, this is akin to a class >> variable. hasValue restrictions are defined on the class and applies >> "automatically" to all instances. This is basically what cls-hv1 >> does. cls-hv2 allows you to also infer that anything with the >> property-value pair is a member of the class. >> >> -- Scott >> >> On Aug 25, 3:39 pm, Leonard Jacuzzo <[email protected]> wrote: >> > Hello list, >> > >> > Thank you for all of the help that you have been to me in understanding >> how >> > to use SPARQL for rule creation. >> > >> > I have a few questions. >> > >> > I was looking over the specification of OWL-RL athttp:// >> topbraid.org/spin/owlrl-all.html >> > >> > The rule cls hv1 has a typo in it. The last triple in the WHERE clause >> has >> > not function in the rule and is not part of the W3C specification. That >> is >> > "?u?p ?v should be removed. Here is the rule as it stands. >> > # cls-hv1 >> > CONSTRUCT { >> > ?u ?p ?y .} >> > >> > WHERE { >> > ?x owl:hasValue ?y . >> > ?x owl:onProperty ?p . >> > ?u a ?x . >> > ?u ?p ?v . >> > >> > } >> > >> > I am also confused by the following rule, which conforms to the W3C, but >> > makes no sense to me. Can you explain it to me? >> > Here is the rule: >> > # cls-hv2 >> > CONSTRUCT { >> > ?u a ?x .} >> > >> > WHERE { >> > ?x owl:hasValue ?y . >> > ?x owl:onProperty ?p . >> > ?u ?p ?y . >> > >> > } >> > >> > The reason that I am confused is that it seems easy to come up with a >> > counter example. E.G. imagine that the class "Orange' hasvalue .25 on >> the >> > property "hasPrice" (so oranges are priced at 25 cents) Further imagine >> that >> > some individual lime(u) hasPrice .25. It does not follow from this that >> Lime >> > (u) is a lemon. >> > >> > What am I missing in my understanding of this rule? >> > >> > BTW: what does it mean to assert that a class X hasValue y on property >> P? >> > The class Orange does not have a price, only individual oranges have a >> > price. Should this be a Orange is a subclass of the restriction on the >> > property "hasPrice" to the value 25 cents? When would a person use the >> > structure in the WHERE clause? >> > >> > I have one more question about rules, but I will wait until I think some >> > more. >> > >> > Thank you for reading this. Any help will be great, >> > LFJ >> >> -- >> You received this message because you are subscribed to the Google >> Group "TopBraid Suite Users", the topics of which include TopBraid >> Composer, >> TopBraid Live, TopBraid Ensemble, SPARQLMotion and SPIN. >> To post to this group, send email to >> [email protected] >> To unsubscribe from this group, send email to >> [email protected] >> For more options, visit this group at >> http://groups.google.com/group/topbraid-users?hl=en >> > > -- > You received this message because you are subscribed to the Google > Group "TopBraid Suite Users", the topics of which include TopBraid > Composer, > TopBraid Live, TopBraid Ensemble, SPARQLMotion and SPIN. > To post to this group, send email to > [email protected] > To unsubscribe from this group, send email to > [email protected] > For more options, visit this group at > http://groups.google.com/group/topbraid-users?hl=en > > -- > You received this message because you are subscribed to the Google > Group "TopBraid Suite Users", the topics of which include TopBraid > Composer, > TopBraid Live, TopBraid Ensemble, SPARQLMotion and SPIN. > To post to this group, send email to > [email protected] > To unsubscribe from this group, send email to > [email protected] > For more options, visit this group at > http://groups.google.com/group/topbraid-users?hl=en > -- You received this message because you are subscribed to the Google Group "TopBraid Suite Users", the topics of which include TopBraid Composer, TopBraid Live, TopBraid Ensemble, SPARQLMotion and SPIN. 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