- From: Sarven Capadisli <info@csarven.ca>
- Date: Thu, 08 Mar 2012 11:23:28 -0500
- To: public-lod@w3.org
On 12-03-08 10:35 AM, Antoine Zimmermann wrote: > Le 08/03/2012 16:01, Sarven Capadisli a écrit : >> Hi Antoine, >> >> Thank you for that excellent break down. I have a much better >> understanding now. Of course, only on the surface :) I didn't know about >> punning. >> >> I've decided to go ahead with the switch from skos:exactMatch to >> owl:sameAs in my case for two reasons: >> >> * My resource can easily be seen as the same thing as the other >> resource. That is, the descriptions can be merged and it still makes >> sense, and nothing jumps out at me that suggests otherwise. >> >> * OWL DL is too far down for me to fear the complications. I think the >> benefits here outweigh the possible complications, if any. Fingers >> crossed. :) >> >> Would you mind elaborating on why you think skos:Concept is not >> necessarily a class? > > skos:Concept itself is a class, but instances of skos:Concept do not > need be classes. This is explicit in the SKOS recommendation, at Section > 3.5.1 (http://www.w3.org/TR/2009/REC-skos-reference-20090818/#L896): > > "Other than the assertion that skos:Concept is an instance of owl:Class, > this specification does not make any additional statement about the > formal relationship between the class of SKOS concepts and the class of > OWL classes. The decision not to make any such statement has been made > to allow applications the freedom to explore different design patterns > for working with SKOS in combination with OWL." > > > Best, > AZ That's a great point! Also goes to show that I should follow the seeAlso documents and not rely entirely on the core ontology URI. -Sarven >> >> Thanks again! I'm marking your mail for future reference. >> >> -Sarven >> >> On 12-03-07 03:00 AM, Antoine Zimmermann wrote: >>> If you care about what the OWL spec says and don't want to write >>> something invalid (or inconsistent), you first have to distinguish >>> between OWL DL and OWL Full. >>> >>> In OWL Full, everything is an instance of owl:Thing. Classes, >>> Properties, Literals, Datatypes, etc are instances of owl:Thing. Even >>> owl:Thing itself is an instance of owl:Thing. That is to say that >>> owl:Thing is equivalent to rdfs:Resource. So, owl:sameAs can be used for >>> anything. >>> Which does not mean that it should! >>> >>> In OWL DL, there are restrictions but since OWL 2 is standard, it's been >>> more complicated. owl:Thing does not contain classes. So, in principle, >>> owl:sameAs must not be used to relate an individual to a class. But OWL >>> 2 introduced the idea of "punning" which says that you can use a *class >>> name* as an *individual name*. So, for example, this is legal in OWL 2 >>> DL (Turtle syntax): >>> >>> :c a owl:Class . >>> :x a :c . >>> :x owl:sameAs :c . >>> >>> The fact is that :c on line 2 is a class, while :c on line 3 is an >>> individual. Morever, :c on line 2 and :c on line 3 have absolutely no >>> semantic relationship. They simply have the same name. >>> But again, it's not because it's allowed that it is necessarily good. >>> >>> Now, if you really *need* to say that :a owl:sameAs :b, then by all >>> means do. But remember that this means that :a and :b *is* only one >>> individual. If you don't need to assert this identity, maybe it's better >>> using something like skos:exactMatch. >>> >>> If your application does not treat owl:sameAs in any special way (e.g., >>> you use an OWL reasoner, or you display the owl:sameAs link in a special >>> way) then you really don't need owl:sameAs. If you are doing something >>> special for the owl:sameAs predicate, you have to be conscious of the >>> implications. >>> >>> In any case, there is no problem having a skos:Concept of type owl:Thing >>> in either OWL DL or OWL Full. A skos:Concept is not necessarily a class. >>> >>> >>> AZ >>> >>> Le 07/03/2012 07:43, Sarven Capadisli a écrit : >>>> Hi, >>>> >>>> I'm sure this is talked somewhere, I'd love a pointer if you know any: >>>> >>>> I often see resources of type owl:Class get paired with resources of >>>> type owl:Thing using owl:sameAs. As far as I understand, this is >>>> incorrect since domain and range of owl:sameAs should be owl:Thing. >>>> >>>> I'm tempted to change my resource that is a skos:Concept >>>> skos:exactMatch'ed with a resource of type owl:Thing, and use >>>> owl:sameAs. Sort of like "everyone else is doing it, it should be >>>> okay", >>>> and "don't need to fear the thought police". >>>> >>>> However, I don't wish to do that with a clear conscience, hence, I'd >>>> appreciate it if anyone can shed some light here for me and help me >>>> understand to make an informed decision based on reason (no pun >>>> intended). >>>> >>>> Related to this, I was wondering whether it makes sense to claim a >>>> resource to be of type owl:Class as well as of type owl:Thing, where >>>> may >>>> be appropriate, or one could get away with it e.g., a country. If this >>>> is okay, I imagine it is okay to use owl:sameAs for the subject at hand >>>> and point to yet another thing. >>>> >>>> Thanks all. >>>> >>>> -Sarven >>>> >>>> >>> >>> >> >> >> >
Received on Thursday, 8 March 2012 16:23:59 UTC