- From: Denny Vrandecic <dvr@aifb.uni-karlsruhe.de>
- Date: Thu, 23 Aug 2007 12:01:59 +0200
- To: semantic-web@w3.org
Hi,
I know I probably have a mistake in here, but I am not sure where it is.
Maybe you can help me.
In OWL DL it is possible to say
A(_1).
with _1 being a blank node. It is also possible to say the semantically
equivalent thing
{_1} ⊑ A
or, if you don't have Unicode:
{_1} \sqsubseteq A
which means that the nominal consisting of the blank node _1 is a
subclass of the class A.
Now, since this is possible, why can't I say
∃father.{_1} ≡ ∀sibling.∀father.{_1}
or
\exists father.{_1} \equals \forall sibling. \forall father.{_1}
which supposedly means that if someone has a father, all his siblings
also have to have the same father.
A colleague, Markus Krötzsch, tried to explain me that the problem lies
with the interpretation of the blank node. But then I don't get the
difference to
∃father.{a} ≡ ∀sibling.∀father.{a}
or
\exists father.{a} \equals \forall sibling. \forall father.{a}
or isn't there any?
A bit confused,
denny
Received on Thursday, 23 August 2007 10:02:10 UTC