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Re: Defeasible logic in N3 Rules?

From: Tim Berners-Lee <timbl@w3.org>
Date: Mon, 24 Mar 2008 18:19:22 -0400
Cc: cwm talk <public-cwm-talk@w3.org>, Benjamin Grosof <bgrosof@mit.edu>
Message-Id: <D45E3513-DEEE-4231-B5EF-4CF4A462557C@w3.org>
To: Jeff Thompson <jeff@thefirst.org>

Jeff,

I have always held out for the design goal that two sets of rules,  
each of which is useful in its own local domain, can be combined into  
a large set.  This requires monotonicity.   Ben Grosof and I have  
argued about this for years, as his systems (like sweetjess) typically  
rely on the sort of prioritization you describe.  In fact, if you have  
a given set of the rules with priorities you can always compile them  
down to a nested expression in monotonic logic.   the problem is in an  
open world like the web, you never know all the rules.  In a non-mon  
world, you can't really do anything as you don't know if somewhere  
something might be out-prioritizing you.   So long as you exlictly  
close the world, by saying which data sources and rulesets are  
relevant, then you can talk about defaults and priorities - and  
negation as failure.  We have called this 'scoped' negation as failure.

Tim

On 2008-03 -22, at 14:08, Jeff Thompson wrote:

>
> Has there been any thought about resolving conflicting conclusions  
> in N3 Rules?
> This paper makes a good case for defeasible logic which lets you  
> prioritize rules
> which may produce conflicting conclusions.
> http://iskp.csd.auth.gr/publications/DKE-Kontopoulos.pdf
>
> Specifically, has there been thought of a non-monotonic version of  
> log:implies
> which allows a superiority relation among rules?
>
> - Jeff
>
Received on Monday, 24 March 2008 22:19:57 GMT

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