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Re: PROV-ISSUE-45: isDerivedFrom and IVPof are transitive. [Conceptual Model]

From: Graham Klyne <GK@ninebynine.org>
Date: Thu, 28 Jul 2011 14:31:10 +0100
Message-ID: <4E31649E.7080905@ninebynine.org>
To: "Cresswell, Stephen" <stephen.cresswell@tso.co.uk>
CC: Paolo Missier <Paolo.Missier@ncl.ac.uk>, public-prov-wg@w3.org
I don't believe that the mere *overlap* of time intervals is sufficient (of 
itself) to assert the IVP relation.  I think containment would be needed.

#g
--

Cresswell, Stephen wrote:
> 
> 
>  
> 
> Paolo,
> 
>  
> 
> I don’t see how IVPof can be usefully considered transitive in its 
> current definition, as I think it would be possible for some 
> transitively-derived IVPof relations to be valid only over empty time 
> intervals.  This is because B IPVof A is defined to only hold over the 
> temporal intersection of A and B, but the relation of having non-empty 
> temporal intersection is itself not transitive. 
> 
>  
> 
> For example, we can have three time intervals X, Y, Z such that X 
> overlaps Y, Y overlaps Z, but X is disjoint from Z.
> 
> Then if we have bobs Bx, By, Bz which hold over the respective time 
> intervals, and we asserted
> 
> Bx IVPof By
> 
> By IVPof Bz
> 
> … then transitivity would allow us to derive
> 
> Bx IVPof Bz
> 
> … but that is dubious because it would hold only over the temporal 
> intersection of X and Z, which is empty.
> 
>  
> 
> I was hoping that the definition of B IVPof A would turn out to require 
> that the time interval of B was contained in the time interval of A.  I 
> think that would be a simpler and better-behaved relation, which should 
> be glorified with a name, even it’s not “IVPof”.
> 
>  
> 
> Stephen Cresswell
> 
> Tel:  +44 (0) 01603 69 6926
> 
> Web:  www.tso.co.uk <http://www.tso.co.uk/>
> 
>  
> 
> * From: * public-prov-wg-request@w3.org 
> [mailto:public-prov-wg-request@w3.org] *On Behalf Of *Paolo Missier
> *Sent:* 25 July 2011 12:30
> *To:* public-prov-wg@w3.org
> *Subject:* Re: PROV-ISSUE-45: isDerivedFrom and IVPof are transitive. 
> [Conceptual Model]
> 
>  
> 
> Khalid
> 
> I don't think we have ever agreed on that, but I should really check the 
> voting history. The latest definition of IVP-of (or complement-of) is 
> sufficiently precise (i.e., algorithmic) that transitivity follows, but 
> derivation is purely asserted and as such there is no ground to say that 
> it is transitive -- unless we say axiomatically that it should be.
> 
> -Paolo
> 
> 
>      
> 
>      
> 
>  PROV-ISSUE-45: isDerivedFrom and IVPof are transitive. [Conceptual Model]   
> 
>      
> 
>   http://www.w3.org/2011/prov/track/issues/45    
> 
>      
> 
>  Raised by: Khalid Belhajjame   
> 
>  On product: Conceptual Model   
> 
>      
> 
>      
> 
>  If we agree that “isDerivedFrom” and “IVPof” are transitive, then I would suggest that this should be specified in the model working draft.   
> 
>      
> 
>  khalid   
> 
> 
> 
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Received on Thursday, 28 July 2011 13:36:10 GMT

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