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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 16:49:09 +0100
To: "'Rinke Hoekstra'" <hoekstra@uva.nl>
Cc: "'OWL 2'" <public-owl-wg@w3.org>
Message-ID: <A56F4BD2A10C4A09AA8DCA76DD723CAA@wolf>

Hello,

The word "possibly" denoted the fact that you could have either the simple inclusions, or, if you wanted, you could have property
chains. I agree that this was ambiguous, so I just changed it to "object property inclusion (<span
class="nonterminal">SubObjectPropertyOf</span>) with or without property chains". I hope things are clear now.

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 16:44
> To: Boris Motik
> Cc: 'OWL 2'
> Subject: Re: Top property in property chains for the EL fragment.
> 
> 
> Hi Boris,
> 
> On 17 sep 2008, at 17:21, Boris Motik wrote:
> > 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.
> 
> Ok thanks (it got me a bit confused).
> 
> Along the same lines, this means that property chains are allowed in
> SubObjectProperty statements, as there are no syntactic restrictions
> that disallows them. Perhaps the 'possibly' should then be removed in
> [3] to make the line less ambiguous.
> 
> Best,
> 
> 	Rinke
> 
> >
> >
> > 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
> >> -----------------------------------------------
> >>
> >>
> >>
> >>
> >
> 
> -----------------------------------------------
> 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 15:51:08 UTC

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