Hi, David, Bernard, Kingsley,
Thank you for your answers. Bernard you're right, I fell into the trap. No way to define a "canonic" prop with the intended semantics and make it a subProp of owl:sameAs because if you state s :canonic canonicRes . you can infer canonicRes :canonic s . Regarding con:preferredURI, "a priori dedicated to agents": I would have preferred property described by "the URI that the owner of a resource recommends to identify the resource in question". Very close to xhv:canonical, I guess. Best, fps De : Kingsley Idehen [mailto:[email protected]] Envoyé : vendredi 4 janvier 2013 01:39 À : [email protected] Objet : Re: canonicURI property On 1/3/13 6:24 PM, Bernard Vatant wrote: Hi folks Sorry to differ with Kingsley on this, but this is an old trap :) On 1/3/13 11:19 AM, SERVANT Francois-Paul wrote: what property should be used to write in RDF links such as those denoted by <link rel="canonical" href="...">? Is it con:preferredURI? Although con:preferredURI is a priori dedicated to agents, I guess you can extend its use to other resources, since the domain is left open in this vocabulary. If the creator TBL is lurking, he can confirm his intentions :) Why is the object of con:preferredURI a string and not a resource? Because the preferred URI value is what it is : a URI, hence a rdf:Literal, and not the resource named/identified by this literal con:preferredURI is a simple rdf:Property because contact vocabulary is expressed in RDFS, but it's clear by its definition ... <rdf:Property rdf:about="http://www.w3.org/2000/10/swap/pim/contact#preferredURI";> <comment>A string which is the URI a person, organization, etc, prefers that people use for them.</comment> <label>preferred</label> </rdf:Property> ... that if this vocabulary were to be translated in OWL, it would become a owl:DatatypeProperty with range xsd:anyURI I have in a linked data set URIs in my namespace that are owl:sameAs, and among them one which is a "canonical one". When dereferencing one of these URIs, I want to state in the returned RDF something like: :OneOfThoseURIs x:canonicURI :TheCanonicOne. and then have triples about :TheCanonicOne You can't do that, because :TheCanonicOne is a rdf:Literal which cannot be in subject position (so far ...) My goal is to make clear that the preferredURI (the one that should be used - and the one that actually is used in the returned RDF) is :TheCanonicOne. Of course: x:canonicURI rdfs:subPropertyOf owl:sameAs. Of course not! This is the trap. You confuse the URI (the string) with the resource it identifies. What you mean is that all sameAs resources share the preferred URI. For example IF :x con:preferredURI 'myNiceURI' THEN ( :y con:preferredURI 'myNiceURI'' ) <=> ( :y owl:sameAs :x ) A system can rely on the preferredURI value e.g., to use it as the rdf:about value in a RDF/XML. But that's all. If you have owl:sameAs declarations, all sameAs URIs would be equivalent in rdf:about with the same semantics. preferredURI is akin to skos:prefLabel, no more, no less. Best regards Bernard Bernard Vatant Vocabularies & Data Engineering Tel : + 33 (0)9 71 48 84 59 Skype : bernard.vatant Blog : the wheel and the hub<http://blog.hubjects.com/> -------------------------------------------------------- Mondeca 3 cité Nollez 75018 Paris, France www.mondeca.com<http://www.mondeca.com/> Follow us on Twitter : @mondecanews<http://twitter.com/#%21/mondecanews> Yes, I stated: :canonicalURI owl:equivalentProperty xhv:canonical; rdfs:subPropertyOf owl:sameAs. ## for good measure xhv:canonical rdfs:subPropertyOf owl:sameAs . Note, my instinctive thinking was: x:canonicalURI :notOwlSameAs :canonicalURI . :-) So the question, as I now see it, is this: What does xhv:canonical denote ? Answer: a URI, an Identifier rather than an entity denoted by said Identifier. Conclusion: You are correct :-) -- Regards, Kingsley Idehen Founder & CEO OpenLink Software Company Web: http://www.openlinksw.com Personal Weblog: http://www.openlinksw.com/blog/~kidehen Twitter/Identi.ca handle: @kidehen Google+ Profile: https://plus.google.com/112399767740508618350/about LinkedIn Profile: http://www.linkedin.com/in/kidehen -- Disclaimer ------------------------------------ Ce message ainsi que les eventuelles pieces jointes constituent une correspondance privee et confidentielle a l'attention exclusive du destinataire designe ci-dessus. Si vous n'etes pas le destinataire du present message ou une personne susceptible de pouvoir le lui delivrer, il vous est signifie que toute divulgation, distribution ou copie de cette transmission est strictement interdite. 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