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Re: nonmon mapping and punning

From: Alan Ruttenberg <alanruttenberg@gmail.com>
Date: Thu, 6 Mar 2008 03:13:47 -0500
Message-Id: <BABF6EC6-63EE-430C-AA70-ED4E58500F01@gmail.com>
Cc: "Michael Schneider" <schneid@fzi.de>, "Web Ontology Language ((OWL)) Working Group WG" <public-owl-wg@w3.org>, "Jeremy Carroll" <jjc@hpl.hp.com>
To: Bijan Parsia <bparsia@cs.man.ac.uk>

I thought the issue wasn't in adding or removing one triple, but  
rather the general truth maintenance issue. Namely you have rules  
that depend on certain triples existence as antecedents. You don't  
necessarily known when these rules fire, relative to when you need to  
retract a statement. If adding something causes you to retract a  
statement, then you want to also retract all triples that were added  
based on rules which had the retracted triple as antecedent.

The mechanism you refer to below is possibly adequate to retract a  
triple (possibly because it isn't clear to me from the spec whether  
triples added by a reasoner would trigger the event). But it isn't  
adequate to retract the triples that were added as a result of rules  
that fired based on it.

-Alan

On Mar 6, 2008, at 2:32 AM, Bijan Parsia wrote:

>
> On Mar 4, 2008, at 5:31 PM, Michael Schneider wrote:
>
>> [related to ISSUE-68]
> [snip]
>> I don't think that Jeremy really meant that it is technically  
>> impossible,
>> but more that it doesn't match the general concepts behind Jena,  
>> which is an
>> RDF framework after all.
> [snip]
>
> Which has specific support for specifically this sort of feature.  
> This is the part I don't understand.
>
> [snip]
>
> Michael...I'm sorry, but I don't quite see what all that had to do  
> with the reactive event framework. In particular, I don't quite see  
> why you detoured into the "OWL View" part of Jena.
>
> Afaict, Jena has specific support which makes it quite easy to  
> delete some other triples when you add a triple. I point to it again:
> 	http://jena.sourceforge.net/how-to/event-handler.html
>
> So, I fail to see how the non-monotonicity of the mapping is a deep  
> problem for Jena or that Jena, in principle and by design, lacks  
> the facilities to handle this. Note that since Jena has add and  
> delete operations, even without this sort of event listeners, it  
> would be *technically* possible, perhaps straightforward in the  
> naive case, to handle the non-monotonicity of the mapping at the  
> parser level. The unpleasant bit there is that one would have to  
> use a shadowed or variant add statement. With event support, you  
> don't have to do that.
>
> (I'm not arguing pro or con the way the mapping is right now, I'm  
> merely trying to figure out the impact on implementations.)
>
> Cheers,
> Bijan.
>
Received on Thursday, 6 March 2008 08:14:39 GMT

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