- From: Uli Sattler <sattler@cs.man.ac.uk>
- Date: Tue, 26 Aug 2008 18:43:46 +0100
- To: Jeff Thompson <jeff@thefirst.org>
- Cc: public-owl-dev@w3.org

On 26 Aug 2008, at 16:50, Jeff Thompson wrote: > > Uli Sattler wrote: > >> In > >> other words, suppose you have the OWL 2 axiom: > >> > >> ObjectProperty: childRelatedToBrother > >> SubPropertyChain: hasParent o owl:TopObjectProperty o hasBrother > >> > >> would that be the same as this rule: > >> hasParent(x, y) ^ hasBrother(w, z) -> childRelatedToBrother(x, z) > >> > >> In other words, the parent of x does not need to be the same as > the brother of z. > >> > > > > Now this example looks very strange indeed: could you explain to > us what the idea behind it is? Cheers, Uli > > I'm trying to fill out the table of combinations of variables for > rules > which can be converted to axioms without variables. You already have: > > hasParent(x, y) ^ hasBrother(y, z) -> hasUncle(x, z) > > and > > hasPerformer(x, y) ^ loves(y, y) -> hasPrimadonna(x, y) > > How about this one: > > hasParent(x, y) ^ ownsCastle(y, z) -> hasRichParent(x, y) > hm, in this case, I would rather add the following axiom: hasParent some (owns some Castle) subClassOf HasRichParent or rather (owns some Castle) subClassOf Rich hasParent some Rich subClassOf HasRichParent > Notice that the consequent has (x, y), not (x, z) so that z is > unbound. I think this > can done by turning ownsCastle(y, z) into a class description for y > like OwnsCastle(y) with > a someValuesFrom restriction on ownsCastle > > Class: OwnsCastle SubClassOf: ownsCastle some owl:Thing > > Then the rule becomes one which can be converted to OWL: > > hasParent(x, y) ^ OwnsCastle(y) -> hasRichParent(x, y) > > You see what I'm getting at. In general, I'm interested in the way > that > "Rewriting Rules into SROIQ Axioms" turns > rules with variables into axioms without variables. it's described in the papers mentioned earlier...but I think have a question in mind but you don't want to go through the algorithm's details? > Is there other work which turns > all the forms of rules into axioms without variables, even if they > aren't tractable OWL axioms? hmmm, no: all approaches only work for certain kinds of rules, and you have to be even careful to check, when you translate a *set* of rules, that the result doesn't violate the 'regularity restrictions' of OWL2 subproperty axioms... Cheers, Uli > > > - Jeff > > > > >

Received on Tuesday, 26 August 2008 17:42:30 UTC