W3C home > Mailing lists > Public > public-owl-wg@w3.org > July 2008

Re: Issue-114

From: Rinke Hoekstra <hoekstra@uva.nl>
Date: Tue, 1 Jul 2008 15:07:06 +0200
Cc: OWL Working Group WG <public-owl-wg@w3.org>
Message-Id: <05AC0CA4-1D67-49E6-8F74-9DEE25A2EAD3@uva.nl>
To: Alan Ruttenberg <alanruttenberg@gmail.com>


On 1 jul 2008, at 14:42, Alan Ruttenberg wrote:
> As an aside, I always have have a bit of trouble with "getting"  
> rigid and anti-rigid properties. When I asked Guardino about this he  
> said that rigidity isn't something in reality - it is part of your  
> theory of ontology.  But then Pat Hayes seemed to disagree and says  
> that no, many people consider them not to be a choice. Then there is  
> the aspect of whether to think about them in terms of necessity in  
> possible worlds (but then the question of which possible worlds to  
> quantify over), or as a classification into properties that can vary  
> over time one initially acquired, versus those that can't, assuming  
> one has a theory of the identity of the bearer over time.

That's a nice summary. As a matter of fact, I find the terms a bit  
confusing as well, and that's also why I am doubtful as to whether the  
father property is anti-rigid or just non-rigid. If it were rigid, no  
one could become a father.

> That said, it is a little hard to figure out in what sense Father is  
> anti-rigid. Are you saying that Father is anti-rigid because it is  
> possible that in some possible world you are not a father? In the  
> temporal sense, it's hard to imagine "father" role to be dropped, if  
> defined as the property of having fathered a child, although it is  
> possible to imagine it dropped if defined as active involvement with  
> offspring.

I guess I take a rather practical, more monotonic stance, as in  
information management in a knowledge based system. The father  
property is just one of those properties that, when its value alters,  
does not require me to create a new individual of a new type (or move  
the database record to a different table).

> But even though it's true it doesn't feel definitional. But that  
> said, I can imagine one wanting, for modeling purposes, to reify  
> relations.

Agreed. That was the point I was trying to make.

>> Person equiv context_of exactly 1 father
>
> What's the domain of context_of? Or rather, how should I read this  
> in english?

I took the context_of relation from Searle's counts-as rules that  
construct social facts: X counts as Y in the context of C. In Searle,  
C is a system of other social facts and conventions, but it doesn't  
have to be.

>
>> and the role inclusion axiom
>>
>> context_of o played_by -> father
>
> Neither context_of or played_by are specifically father related (or  
> at leas they don't sound so).

You are right: my bad. There should have been a Self restriction on  
the Father class, or either one of the two properties should be father- 
specific.

> I'm going to try to rephrase to see if I've got the basic idea:
>
> One would like to reify a relation and ideally have it be the case  
> that either use of the reified relation or the relation directly,  
> arranges to have the other inferred. If that were the case, we could  
> equate the property to the class, as the instances of the class  
> would be in a 1:1 relation with the pairs of relata. They could, in  
> this sense, be understood to mean the same thing.

Exactly, thanks,

	Rinke

>
> -Alan
>
>

-----------------------------------------------
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 Tuesday, 1 July 2008 13:07:42 UTC

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