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Re: owl:TopObjectProperty in property chains?

From: Uli Sattler <sattler@cs.man.ac.uk>
Date: Wed, 27 Aug 2008 10:51:25 +0100
Cc: public-owl-dev@w3.org
Message-Id: <FEE0A981-52B3-4152-B504-40CACE4FC11A@cs.man.ac.uk>
To: Jeff Thompson <jeff@thefirst.org>

On 27 Aug 2008, at 05:51, Jeff Thompson wrote:

>
> Uli Sattler wrote:
> >
> > 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
>
> The rule "hasParent(x, y) ^ ownsCastle(y, z) -> hasRichParent(x, y)"  
> is trying
> to define the property hasRichParent, but in both these examples,  
> HasRichParent
> is a class, not a property (unless I don't understand the notation).
>

Hi Jeff, I understood this -- but from the context of the example, I  
would have rather modelled it in the 'class'-y way, and I was simply  
trying to get at what the 'real' examples are that motivate these  
questions....

> >> 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?
>
> I am interested in the algorithm details but fear I don't have the  
> proper
> context for what I was reading.  "Tight Integration of Description  
> Logics and Disjunctive Datalog"
> by Rosati talks about integrating DL database with a Datalog rules  
> engine
> but you are still expected to write the rules in Datalog.

aaah, so I can understand your difficulties...you can find a worked- 
out example that tries to explain the differences between OWL and  
rules and their interaction in

B. Motik, U. Sattler, and R. Studer. Query Answering for OWL-DL with  
Rules. In  Proc. of the Third International Semantic Web Conference  
(ISWC 2004), Vol. 3298 of Lecture Notes in Computer Science. Springer- 
Verlag, 2004.
http://www.springerlink.com/content/3ah2ypj3p628ft4m/fulltext.pdf

...and you can find out more about translating *some* rules  
*faithfully* into OWL axioms in

E	Francis Gasse, Ulrike Sattler, Volker Haarslev: Rewriting Rules into  
SROIQ Axioms. Description Logics 2008
http://ceur-ws.org/Vol-353/GasseSattlerHaarslev.pdf

Markus Krötzsch, Sebastian Rudolph, Pascal Hitzler. ELP: Tractable  
Rules for OWL 2. ISWC2008,  2008.
http://korrekt.org/papers/KroetzschRudolphHitzler_ELP_TR_2008.pdf

Markus Krötzsch, Sebastian Rudolph, Pascal Hitzler. Description Logic  
Rules. ECAI2008,  2008.
http://korrekt.org/papers/KroetzschRudolphHitzler_SROIQ-Rules_TR_2008.pdf

> However,
> "Rewriting Rules into SROIQ Axioms" was the first place I heard about
> "rules can be directly embedded into the knowledge base (KB) so
> we do not need a rule format standard".

...we might still want to have a rule standard because the above  
mentioned approaches only work for *certain* rules.

Cheers, Uli

> This is so compelling to me
> but I don't have the background to know if people have been pursuing  
> this
> goal directly for years, or if they haven't whether that's because  
> they
> didn't think of it, or believed it is not possible.
>
>
>
Received on Wednesday, 27 August 2008 09:50:06 GMT

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