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SNAF, NAF, and monotonicity [was: Comments on * DRAFT * Rules...]

From: Dan Connolly <connolly@w3.org>
Date: Wed, 24 Aug 2005 23:01:02 -0400
Message-Id: <cde60d9cffb261df764e32afcbd97a60@w3.org>
Cc: public-rule-workshop-discuss@w3.org
To: Michael Kifer <kifer@cs.sunysb.edu>

On Aug 24, 2005, at 8:11 PM, Michael Kifer wrote:
[...]
> No, you got me wrong. I do believe that nonmonotonicity is important,  
> but
> you already have it in the form of SNAF.

I'm having trouble understanding that. I see it shows up in several of  
your recent messages, e.g.

"SNAF is nonmonotonic."
http://lists.w3.org/Archives/Public/public-rule-workshop-discuss/ 
2005Aug/0029.html

My understanding is that SNAF is monotonic.

Earlier[1] we discussed this example rule...

{ :car.auto:specification log:notIncludes {:car auto:color []}}
     => {:car auto:color auto:black}.

That rule is monotonic; if the antecedent is true, the consequent  
remains
true regardless of how many other things are also true.

[1] car color defaults
http://lists.w3.org/Archives/Public/public-rule-workshop-discuss/ 
2005Jul/0021.html

Your flora-2 translation[2] (for which thanks; I've been studying it  
for a while...)
also seems monotonic:

?X[realColor->?Color] :- ?X[color->?Color]@allAboutCars.
?X[realColor->black] :- not ?X.color[]@allAboutCars.

[2]  
http://lists.w3.org/Archives/Public/public-rule-workshop-discuss/ 
2005Jul/0033.html

Earlier you wrote that
"NAF is a special case of SNAF."
http://lists.w3.org/Archives/Public/public-rule-workshop-discuss/ 
2005Aug/0012.html

I don't see how that's the case. The whole point of SNAF is that the  
scope is
explicit and hence the construct is monotonic. I don't see how to look  
at NAF
as a special case of that.

Monotonicity is an important scaling property of a language, so I'm  
very interested
to understand this point.

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Thursday, 25 August 2005 03:01:06 GMT

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