Re: what are the best primitives for RDF/OWL?

Richard H. McCullough wrote:
> No.  The idea that X and Y are equivalent, but not sameAs,
> means that the context of X and Y are different.
> I think the most meaningful cases will involve classes whose
> instances change over time.
> 
> Think of it this way.  The context of X, denoted by Cx, can
> be viewed as a hierarchy, with X having a place in Cx which
> is determined by its definition.  Ditto for Cy and definition of Y.
> Now we discover that  Cx:X  equivalentClass  Cy:Y, even
> though they have different definitions.
> But they may not be equivalent tomorrow.

Mmm not sure I see the point. Hold on a sec: owl:equivalentClass can be 
inferred? i.e., given two classes A and B, can I infer that A and B have 
the same instances? My guess is that I can do so only if the definitions 
of A and B are equivalent, because just looking at the set of instances 
I know may turn out to be wrong, assuming the open world assumption 
holds. If so, then the equivalentClass is not inferred from a particular 
context, and cannot turn false tomorrow no matter the context.

> Or, we may discover that there are cause-effect reasons for
> the equivalence, and eventually conclude that Cx:X  sameAs  Cy:Y

if owl:equivalentClass cannot be inferred from the set of instances, 
then what's the difference?

Car  owl:sameAs  Automobile is the same as Car owl:equivalentClass 
Automobile, I'd say: the same cars are sold in UK, France and Italy 
(aside: automobile is the translation of car in french as well, isn't 
it?). In what context are their definition not the same or cover 
different sets of instances?

I.

> 
> The morning-star, evening-star example is similar to this.
> 
> I think the example in the OWL document is a bad one.
> I would say   Car  owl:sameAs  Automobile
> 
> Dick
> ----- Original Message ----- From: "Ignazio Palmisano" 
> <ignazio.palmisano@gmail.com>
> To: "Semantic Web at W3C" <semantic-web@w3.org>
> Sent: Thursday, July 10, 2008 6:20 AM
> Subject: Re: what are the best primitives for RDF/OWL?
> 
> 
>>
>> Richard H. McCullough wrote:
>>>
>>> I'd like to modify the focus of "deprecated URIs" a little bit,
>>> and summarize some of the discussion on this list in 2003 time frame.
>>>
>>> First topic: SubClassOf vs. properSubClassOf.
>>> By definition,  X  SubClassOf  Y has two possible meanings.
>>> 1)  X  sameAs Y
>>> 2)  X  properSubClassOf  Y
>>> Although meaning (1) may seem to have nice mathematical properties,
>>> I think it's harmful to always have to "dispose" of that possibility 
>>> when
>>> reasoning about classes.
>>
>> Why use sameAs in this context? It is more appropriate to use 
>> owl:equivalentClass, whose function is exactly that (at least in my 
>> reading of 
>> http://www.w3.org/TR/2004/REC-owl-features-20040210/#equivalentClass).
>>
>> I.
>>
>>
>>
> Dick McCullough
> http://mKRmKE.org/
> Ayn Rand do speak od mKR done;
> knowledge := man do identify od existent done;
> knowledge haspart proposition list;
> mKE do enhance od "Real Intelligence" done;
> 
> 
>

Received on Thursday, 10 July 2008 15:37:57 UTC