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RE: Question about problems with top/bottom property

From: Boris Motik <boris.motik@comlab.ox.ac.uk>
Date: Mon, 2 Jun 2008 15:18:50 +0100
To: "'Rinke Hoekstra'" <hoekstra@uva.nl>, "'Ivan Herman'" <ivan@w3.org>
Cc: "'Bijan Parsia'" <bparsia@cs.man.ac.uk>, "'Alan Ruttenberg'" <alanruttenberg@gmail.com>, "'Michael Schneider'" <schneid@fzi.de>, <public-owl-wg@w3.org>
Message-ID: <002301c8c4bb$94a5a030$7212a8c0@wolf>

Hello,

We don't disagree regarding the computational complexity: the worst-case computational complexity is the same in both cases.

Judging from all the discussion, I am more and more inclined to believe that having the universal property might be convenient in
many cases. I just believe that we should check how this feature fares in practice. To answer that, when I find some free time, I'll
implement it in HermiT and see whether it causes problems in practice.

Regards,

	Boris

> -----Original Message-----
> From: Rinke Hoekstra [mailto:hoekstra@uva.nl]
> Sent: 02 June 2008 14:55
> To: Ivan Herman
> Cc: Bijan Parsia; Alan Ruttenberg; Boris Motik; 'Michael Schneider'; public-owl-wg@w3.org
> Subject: Re: Question about problems with top/bottom property
> 
> 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?
> 
> -Rinke
> 
> 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
> 
> 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 Monday, 2 June 2008 14:20:25 GMT

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