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Top property in property chains for the EL fragment.

From: Rinke Hoekstra <hoekstra@uva.nl>
Date: Wed, 17 Sep 2008 17:09:43 +0200
Message-Id: <30FF0B53-03A9-499C-BF4A-53ABF4A581EE@uva.nl>
To: OWL 2 <public-owl-wg@w3.org>

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 15:10:18 UTC

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