Thanks Scott. I haven't really looked at SPARQL property paths until now, and your examples and explanation make it a lot easier to understand. Property paths seems to solve most of the problems I've had with property chain axioms in the past.
On Aug 25, 4:31 pm, Scott Henninger <[email protected]> wrote: > Gerrit; this is a known limitation for the current set of OWL 2 RL > profile rules, and we plan to fix for 3.6. > > In the meanwhile, I'd suggest you take a look at the much more > expressive SPARQL property paths. Let's take a great grandfather > example where you may express this using property chain axioms as: > > ex:hasGreatGrandFather > owl:propertyChainAxiom > (ex:parent ex:parent ex:father) . > > Using SPARQL property paths you need to specify precisely the same > information needed in a property chain axiom: > > CONSTRUCT {?me :hasGreatGrandFather ?ggfather} > { ?me ex:parent/ex:parent/ex:father ?ggfather . > > } > > Property chain axioms stops there, but you can go much further with > SPARQL. For example, suppose you're trying to link some other > resource to ancestors - like citizenship - and this is modeled in a > couple of ways - :citizenship or :legalCountry. You can specify the > following: > > CONSTRUCT {?me :ancestorCitizenship ?ggparentCitizenship} > { ?me ex:parent/ex:parent/ex:parent/( ex:citizenship | > ex:legalCountry) ?ggparentCitizenship . > > } > > This is a very common modeling pattern, particularly when merging data > from multiple sources, and it just can't be expressed conveniently in > OWL. > > The expressiveness of property paths is much richer that these simple > examples - seehttp://www.w3.org/TR/sparql11-property-paths/. It > provides for inverse links, transitivity, alternative paths and > multiple paths in addition to the harcoded path sequence in property > chains. In fact the above can be expressed as: > ?me ex:parent{3}/(ex:citizenship | ex:legalCountry) ? > ggparentCitizenship . > > ...and you could get the citizenship for all grandparent and > greatgrandparents with: > ?me :parent{2,3}/(ex:citizenship | ex:legalCountry) ? > ggparentCitizenship . > > So there's quite a bit more you can specify with property paths, with > the tradeoff that the expressions are in rules rather than the data, > which is sometimes an advantage. > > -- Scott > > On Aug 25, 8:28 am, Gerrit <[email protected]> wrote: > > > > > > > > > Looking at the definition of OWL 2 property chains in owlrl.spin.rdf: > > > # prp-spo2-2 > > CONSTRUCT { > > ?u1 ?p ?u3 .} > > > WHERE { > > ?p owl:propertyChainAxiom ?x . > > ?x list:length 2 . > > ?x list:index ( 0 ?p1 ) . > > ?x list:index ( 1 ?p2 ) . > > ?u1 ?p1 ?u2 . > > ?u2 ?p2 ?u3 . > > > } > > > it seems that any property chain axiom containing more than two > > properties is not supported. Am I reading this correctly and if so, > > are there plans to extend it in future? > > > Regards, > > Gerrit -- 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
