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Re: class and inviduals

From: Rinke Hoekstra <hoekstra@few.vu.nl>
Date: Wed, 17 Nov 2010 11:13:45 +0100
Cc: Pat Hayes <phayes@ihmc.us>, Marco Colombetti <colombet@elet.polimi.it>, public-owl-dev@w3.org
Message-Id: <2AE5DDA8-5D85-4268-8C34-2ED133132E23@few.vu.nl>
To: Pavel Klinov <pklinov@cs.man.ac.uk>
Hi Pavel,

On 16 nov 2010, at 17:50, Pavel Klinov wrote:
> As for OWL 2, I do agree with Enrico. Punning is a not quite a logical
> pattern - it's a meta-modeling feature and has to be used with care.
> If you pun an object X and a class X they will still be treated as
> separate entities by a reasoner ("X-as-class" and "X-as-individual" if
> you will). It can be confusing, for example, one may place a data
> property assertion on X (as an individual) and then wonder why other
> instances of X (as a subclass) do not inherit that property.

This is indeed what happens if you use punning. However, if you interpret it as OWL 2 Full (without punning), the inheritance wouldn't occur either. 

The fact that some language feature may be confusing is not a very good general argument against using it. 

> At the
> same time other tools, like Protege, may give a false impression that
> "these are really the same thing".

Hm, but for all practical purposes they *are* the same thing, they are just interpreted differently dependent on context. OWL 2 DL reasoners may separate these contexts for efficiency purposes, but an RDFS/OWL 2 Full reasoner or RDF query engine won't. 

This is fine if you ask me... I have yet to come across a situation where this potential confusion had any practical consequences. 



> Apologies if I'm mistaken in my understanding of punning.
> Cheers,
> Pavel
> On Tue, Nov 16, 2010 at 3:08 PM, Pat Hayes <phayes@ihmc.us> wrote:
>> On Nov 16, 2010, at 4:22 AM, Marco Colombetti wrote:
>>> Aldo is right, punning is allowed in OOWL2, but I wonder whether it should be considered as good practice. In my opinion it conceils certain important modelling choices, and is likely to induce confusion.
>>> Any strong opinion about this?
>> Yes, one strong opinion: it is VERY good practice. The ISO Common Logic framework goes slightly further, allowing any 'thing' to be treated simultaneously as an individual, a class or a relation ('property') of any number of arguments; and we have found in many applications that the resulting freedom to express ontological decisions independently from the apparent constraints of the logic is more than 'good' : it represents a quantum jump in ontology engineering.
>> The key point is that 'individual' in a metaphysical sense is one notion, whose merits can be debated; but 'individual' in the logical sense is quite another. The latter means simply 'a member of the universe of discourse' or 'within the scope of quantification'. The traditional 'good practices' typically get these two distinct notions confused, and use syntactic constraints arising from the latter to model the former, to the lasting detriment of good ontological engineering.
>> Pat Hayes
>>> Marco
> --pavel
> http://www.cs.man.ac.uk/~klinovp

Dr Rinke Hoekstra

AI Department         |   Leibniz Center for Law    
Faculty of Sciences   |   Faculty of Law            
Vrije Universiteit    |   Universiteit van Amsterdam
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1081 HV Amsterdam     |   1012 CX  Amsterdam        
+31-(0)20-5987752     |   +31-(0)20-5253497         
hoekstra@few.vu.nl    |   hoekstra@uva.nl           

Homepage: http://www.few.vu.nl/~hoekstra
Received on Wednesday, 17 November 2010 10:14:14 UTC

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