Re: owl:sameAs temptation

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