- From: PL. Miraglia <pierlu.m@gmail.com>
- Date: Mon, 20 Feb 2006 00:53:10 -0600
- To: Bijan Parsia <bparsia@isr.umd.edu>
- Cc: public-owl-dev@w3.org, www-rdf-logic@w3.org
On Feb 19, 2006, at 11:36 AM, Bijan Parsia wrote:
....
>>
>> This is not what I meant. Logically, it defines a class A that is (a
>> subset of) the intersection of the set {x: Ey(Rxy & Py)} and Q. What
>> I was trying to express is instead:
>>
>> {x: Ey(Rxy & Py)} is a subset of Q
>
>
> Ah, but you seem to think that prefix is the way to do it. It's
> not. subClassOf is always infix:
>
> <owl:Restriction>
> <owl:onProperty rdf:resource="#R"/>
> <owl:someValuesFrom rdf:resource="#P"/>
> <rdfs:subClassOf rdf:resource="#Q"/>
> </owl:Restriction>
Thanks, I had miss this about subClassOf.
>
>> I was trying to figure how to express in owl these 2 logical
>> constraints on an arbitrary property (binary predicate) R:
>>
>> 1. (Ex)(Rxy & Qx) => Py
>>
>> 2. (Ey)(Rxy & Py) => Qx
>
> <http://www.mindswap.org/dav/ontologies/bijan/2006/examples/owl-
> dev-2006-feb>
>
> does both.
>
>> (1) is straightforward in owl (or so I thought, perhaps I am wrong
>> there too):
>>
>> <owl:Class rdf:about="#Q>
>> <rdfs:subClassOf>
>> <owl:Restriction>
>> <owl:onProperty rdf:resource="#R"/>
>> <owl:allValuesFrom rdf:resource="#P"/>
>> </owl:Restriction>
>> </rdfs:subClassOf>
>> </owl:Class>
>
> That gives you Qx => (Ey)(Rxy & Py). See my file for the correct
> encoding.
> And didn't you mean "someValuesFrom"?
No i meant allValuesFrom. The meaning is
Qx => (Rxy => Py) , which in turn is equivalent to
(Qx & Rxy) => Py (all variables are universally quantified).
>
>> (2) is the one I have a question about. It seems that it can be
>> expressed in the "straightforward" form of (1), provided that IR (the
>> inverse of R) is used.
>
> Hmm. I missed the swap of the variables.. Yes, you need an inverse
> in order to bind the first argument of a property with a nested
> quantifier.
>
>> But is the inverse necessary?
>
> Yes. And, unfortunately, in owl you don't have an inverse operator
> (as is standard in DLs), so you have to coin a name for the
> inverse. Curse RDF! :)
>
> Cheers,
> Bijan.
>
This was quite helpful. Thanks,
--
Pierluigi Miraglia
@home Austin, Tex.
Received on Monday, 20 February 2006 06:53:22 UTC