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RE: Top property in property chains for the EL fragment.

From: Boris Motik <boris.motik@comlab.ox.ac.uk>
Date: Wed, 17 Sep 2008 16:21:37 +0100
To: "'Rinke Hoekstra'" <hoekstra@uva.nl>, "'OWL 2'" <public-owl-wg@w3.org>
Message-ID: <F9C67357043A4F87A345FEFE4A013CFF@wolf>

Hello,

Yes, this is intentional. The goal in the design of all the profiles of OWL 2 was to make them syntactic fragments of OWL 2 DL;
otherwise, the entire language hierarchy becomes quite messy. As a consequence, the restrictions on not using owl:TopObjectProperty
in EL++ is "unnecessarily"; however, hardly seems like a reason for concern.

Regards,

	Boris

> -----Original Message-----
> From: public-owl-wg-request@w3.org [mailto:public-owl-wg-request@w3.org] On Behalf Of Rinke Hoekstra
> Sent: 17 September 2008 16:10
> To: OWL 2
> Subject: Top property in property chains for the EL fragment.
> 
> 
> Hi,
> 
> After reading Uli's response to a question from Jeff Thompson (below),
> I just checked the global restrictions section for the EL profile in
> [1]. It doesn't mention the fact that the top-property is allowed in
> role chains in the EL fragment (but not in DL itself [2]). Is this
> intentional?
> 
> The EL feature overview states "possibly involving property chains"
> for SubObjectProperty [3]... does this mean we don't know whether
> property chains can be used in EL? Or that using property chains is
> allowed?
> 
> -Rinke
> 
> [1] http://www.w3.org/2007/OWL/wiki/Profiles#Global_Restrictions
> [2] http://www.w3.org/2007/OWL/wiki/Syntax#Global_Restrictions_on_Axioms
> [3] http://www.w3.org/2007/OWL/wiki/Profiles#Feature_Overview
> 
> 
> Begin forwarded message:
> 
> > Resent-From: public-owl-dev@w3.org
> > From: Uli Sattler <sattler@cs.man.ac.uk>
> > Date: 29 augustus 2008 11:33:31 GMT+02:00
> > To: Jeff Thompson <jeff@thefirst.org>
> > Cc: public-owl-dev@w3.org
> > Subject: Re: owl:TopObjectProperty in property chains?
> >
> >
> >
> > On 28 Aug 2008, at 08:52, Jeff Thompson wrote:
> >
> >>
> >> Thanks for the references!  These are right on target.  I will
> >> study them.
> >> In "Tractable Rules for OWL 2", top of page 6, there is the example
> >> to translate:
> >>
> >> NutAllergic(x) ? NutProduct(y) ? dislikes(x, y)
> >>
> >> to
> >>
> >> NutAllergic ? ?RNutAllergic.Self
> >> NutProduct ? ?RNutProduct.Self
> >> RNutAllergic ? U ? RNutProduct ? dislikes
> >>
> >> I'm temporarily gratified that this has the use of the universal role
> >> in a role chain, similar to my original example (hence the name of
> >> this
> >> thread).  But as I study the paper, I suspect it will say that this
> >> example is not a tractable rule for OWL 2 (despite the title of the
> >> paper).
> >>
> >
> > Hi Jeff, I didn't mention this example/way of approximating roles in
> > my previous emails because they require, additionally, some lengthy
> > explanation about when you can and can't use them without violating
> > the 'regularity' condition i mentioned......this regularity
> > condition ensures decidability of reasoning and that our reasoning
> > techniques work.
> >
> > The thing is that, in OWL2  DL, you cannot use owl:TopObjectProperty
> > in subproperty chains -- you could do so in EL++, a DL described in
> >
> > http://www.webont.org/owled/2008dc/papers/owled2008dc_paper_3.pdf
> >    Pushing the EL Envelope Further. Franz Baader, Sebastian Brandt,
> > and Carsten Lutz. In Proc. of the Washington DC workshop on OWL:
> > Experiences and Directions (OWLED08DC), 2008.
> >
> > If you want to know more about this, let me know.
> >
> > Cheers, Uli
> >
> >
> >> Thanks again,
> >> - Jeff
> >>
> >> Uli Sattler wrote:
> >>>> >> 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
> >>> *
> >>
> >>
> >>
> >
> 
> -----------------------------------------------
> Drs. Rinke Hoekstra
> 
> Email: hoekstra@uva.nl    Skype:  rinkehoekstra
> Phone: +31-20-5253499     Fax:   +31-20-5253495
> Web:   http://www.leibnizcenter.org/users/rinke
> 
> Leibniz Center for Law,          Faculty of Law
> University of Amsterdam,            PO Box 1030
> 1000 BA  Amsterdam,             The Netherlands
> -----------------------------------------------
> 
> 
> 
> 
Received on Wednesday, 17 September 2008 15:23:18 UTC

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