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Re: Reified relations in OWL

From: Pat Hayes <phayes@ihmc.us>
Date: Fri, 26 Feb 2010 17:09:00 -0600
Cc: "Uli Sattler" <sattler@cs.man.ac.uk>, <public-owl-dev@w3.org>
Message-Id: <8F2C97E5-A8FD-40D1-9BAB-A0758A4D173C@ihmc.us>
To: "Paul Oude Luttighuis" <Paul.OudeLuttighuis@novay.nl>

On Feb 26, 2010, at 10:16 AM, Paul Oude Luttighuis wrote:

> Dear Uli,
>
> Thanks for your swift reply.
>
> I'm hesitant about extensively elaborating on our modelling approach  
> in this forum. It's not the place. If you like, we can do that via  
> direct e-mail.
>
> But, to answer your last question: basically, I would like relations  
> to be able to participate in relations themselves. In fact, in the  
> modelling approach we study, this is the rule, not the exception.  
> Relations are hence first-class citizens, or even, the only  
> citizens ... Each concept is represented by a relation that connects  
> the concepts it is existence-dependent upon. So, it requires  
> relations to have their own instances. This is what I know as  
> "reified relations".
>
> We are looking for modelling languages that might nicely express  
> such reified-relations-only models. OWL is only one of them. Our  
> first concern is not reasoning, but plain representation, preferably  
> with a nice graphical syntax.
>

Apart from that last requirement, the purely logical aspects of what  
you describe are probably best handled by ISO Common Logic, which   
treats all relations and classes as fully fledged individuals, which  
can themselves stand in other relationships, be included in classes,  
etc., without restriction; moreover, the same name can be used for a  
class, relation and individual, so that relations which apply to  
themselves, etc., are OK. CL has the advantage over UML of  having a  
very exactly specified semantics, which generalizes the OWL model  
theory quite precisely. See ISO/IEC 24707 (available free as a PDF  
download from the ISO site.)

Pat Hayes

PS. Your use of 'reified' is not the standard use, and is going to go  
on causing confusion. I'd suggest a different terminology. BTW, you  
should also check out the new OWL 2 standard, which allows 'punning'  
between classes, properties and individuals. This might provide the  
functionality you need.


> Does this help?
>
> Regards,
>
> Paul
>
> From: Uli Sattler [mailto:sattler@cs.man.ac.uk]
> Sent: vrijdag 26 februari 2010 15:24
> To: Paul Oude Luttighuis
> Cc: public-owl-dev@w3.org
> Subject: Re: Reified relations in OWL
>
>
> On 25 Feb 2010, at 21:53, Paul Oude Luttighuis wrote:
>
>> Dear OWL mailing list,
>>
>> In a current project, we take an approach to semantic modelling  
>> based on reified relations only. In that context, I am looking for  
>> ways of using reified relations in OWL. I am aware of the ways of  
>> mimicking reified relations proposed in http://www.w3.org/TR/swbp-n-aryRelations/ 
>> , but these yield awkward models. Also, such mimicking takes away  
>> the graphical visualisations we need, as these tend (as in Protégé)  
>> to visualise the subtyping hierarchy only, not the relations  
>> (properties). In our case, subtyping is refrained from/not  
>> interesting.
>
> sorry for skipping over your initial question: why would you refrain  
> from 'subtyping'?! The fact that you use the term 'subtyping' seems  
> to indicate a misunderstanding of the OWL semantics...so perhaps  
> this should be clarified first: e.g., in OWL, if you define the  
> class "Waterbirds" as those Birds who live close to water, and Ducks  
> as those Birds who say quack and live close to water, then the  
> subclass relationship between Ducks and Waterbirds will be entailed,  
> and thus inferred by the reasoner...as a consequence, every instance  
> of Duck will also be an instance of Bird, automatically, simply due  
> to the OWL semantics...
>
> Now, perhaps you explain your 'reified relation' scenario a bit  
> more: I assume you want to model n-ary relations/tuples, for n>2? Do  
> you have an example?
>
> Cheers, Uli
>
>>
>> Am I overlooking something. Can anybody point me to more natural  
>> ways of modelling and graphically representing reified relations  
>> with OWL?
>>
>> I'd be grateful for your suggestions.
>>
>> Best regards!
>> Paul
>>
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>>
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>>
>>
>

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Received on Friday, 26 February 2010 23:09:36 GMT

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