Re: owl:sameAs temptation

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
>
>


-- 
Antoine Zimmermann
ISCOD / LSTI - Institut Henri Fayol
École Nationale Supérieure des Mines de Saint-Étienne
158 cours Fauriel
42023 Saint-Étienne Cedex 2
France
Tél:+33(0)4 77 42 83 36
Fax:+33(0)4 77 42 66 66
http://zimmer.aprilfoolsreview.com/

Received on Wednesday, 7 March 2012 08:00:40 UTC