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Re: Question about problems with top/bottom property

From: Rinke Hoekstra <hoekstra@uva.nl>
Date: Mon, 2 Jun 2008 15:55:16 +0200
Cc: Bijan Parsia <bparsia@cs.man.ac.uk>, Alan Ruttenberg <alanruttenberg@gmail.com>, Boris Motik <boris.motik@comlab.ox.ac.uk>, "'Michael Schneider'" <schneid@fzi.de>, public-owl-wg@w3.org
Message-Id: <5920CEEF-D66F-4A20-A30D-6BBDBF0BE148@uva.nl>
To: Ivan Herman <ivan@w3.org>

Topprop or not topprop, that's the question,

It seems Boris and Ulrike disagree on the computational complexity of  
having the universal property. Could someone please explain?

Do we already have some idea of the consequences of adding the bottom  
property, computationally speaking?

As I understand, we can already simulate topprop using existing  
constructs, can we do the same for botprop?


Tracker: this is related to ISSUE-112

On 2 jun 2008, at 15:15, Ivan Herman wrote:

> Bijan, Alan,
> thanks. I think I get it:-)
> Ivan
> Bijan Parsia wrote:
>> On 2 Jun 2008, at 13:16, Ivan Herman wrote:
>>> Alan Ruttenberg wrote:
>>>> Is there any reason not to include bottom role? There is a  
>>>> debugging benefit to computing equivalentProperty to bottom role.
>>> I must admit I do not understand what you mean here.
>>> In general, I would like to understand the clear benefit the top  
>>> and bottom role would bring to OWL users. At the moment, it is  
>>> unclear to me.
>> [snip]
>> We have had extensive discussion on this, so perhaps as summary is  
>> due.
>> From a UI perspective, Top and Bottom properties add symmetry  
>> (i.e., analogues to Thing and Nothing) and thus a more uniform UI.  
>> For example, right now, it is rare (unknown?) for reasoners to  
>> report unsatisfiable properties (which do occur). A natural way to  
>> report this is to show them as equivalent to or subsumed by a  
>> Bottom property (in analogy with how unsatisfiable classes are  
>> handled).
>> Similarly, I find users adding an artifical top property (or asking  
>> for one) just to help organize their properties. (I find this a bit  
>> odd, personally, but that's what it is.)
>> From an expressiveness point of view see:
>>    http://www.w3.org/2007/OWL/wiki/Universal_Property
>> In general, TopProp (my new favored name :)) allows one to express  
>> co-existence constraints *without* specing a particular relation  
>> between the two entities. For example, you might wish to express  
>> that if there is a disease occurrence then there is a cause (germ,  
>> poison, trauma, genetic defect) without necessarily having a "local  
>> top" causal property (i.e., a generic caused by):
>>    DiseaseOccurrence sub (someValuesFrom owl:universal owl:Thing)
>> (or some more specific class of causal agents).
>>    DiseaseAfterTraumaOccurrence sub (someValuesFrom owl:universal  
>> Trauma)
>> (Where the way the trauma causes the disease might be unspecified  
>> or one of a number of disjoint mechanism).
>> In this case, you can capture the structure by other means  
>> (including simulating the TopProp). But it does seem more direct  
>> and flexible.
>> Cheers,
>> Bijan.
> -- 
> Ivan Herman, W3C Semantic Web Activity Lead
> Home: http://www.w3.org/People/Ivan/
> PGP Key: http://www.ivan-herman.net/pgpkey.html
> FOAF: http://www.ivan-herman.net/foaf.rdf

Drs. Rinke Hoekstra

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Received on Monday, 2 June 2008 13:55:53 UTC

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