- From: <jos.deroo.jd@belgium.agfa.com>
- Date: Wed, 7 Mar 2001 14:56:53 +0100
- To: sandro@w3.org
- Cc: www-rdf-logic@w3.org, timbl@w3.org
> > No, that's not what [] means - (you can't just remove them!) they mean...
> You can remove them if you replace them with an existentially
> quantified variable, yes?
I think so (in so far one can think while having fever ...)
> And you can remove an existentially quantified variable in an asserted
> context by replacing it with a new term (that is, by skolemization),
> right?
Well, you could replace that existentially quantified variable with a
(Skolem) constant if it is not falling within the scope of universally
quantified variables. In that case you can replace it with a (Skolem)
function (which has as arguments those universally quantified variables.
BTW this thread is actually about function terms ...
How could we express these Skolem functions?
> In another context, like a negated context or a query, I agree
> skolemization would be wrong. I guess I should have been more explicit.
Sandro, what do you mean with "negated context"?
I could understand that negation changes the "kind" of quantifier (I mean
a universally quantified variable becomes an existentally quantified
variable and vice versa).
I also think that so called "negation-verbs" such as in TimBL example
</etc/passwd.rdf> log:doesntSay { :<#timbl> unix:inGroup <#www> }.
is a very good thing to use (it was actually the only way we could
deal with paradoxes like the Russell set paradox
http://www.agfa.com/w3c/euler/russell.axiom.n3
(where :keine is meaning "not an element of"))....
--
Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/
Received on Wednesday, 7 March 2001 08:57:24 UTC