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

From: Rinke Hoekstra <hoekstra@uva.nl>
Date: Wed, 17 Sep 2008 17:58:41 +0200
Cc: "'OWL 2'" <public-owl-wg@w3.org>
Message-Id: <6A2C5BFF-CC2F-4218-BD0D-F1948DCD7ED2@uva.nl>
To: "Boris Motik" <boris.motik@comlab.ox.ac.uk>

Excellent, thanks!

-Rinke

On 17 sep 2008, at 17:49, Boris Motik wrote:

> 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
>> -----------------------------------------------
>>
>>
>>
>>
>

-----------------------------------------------
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 15:59:24 UTC

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