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

From: <jos.deroo@agfa.com>
Date: Thu, 25 Aug 2005 14:02:48 +0200
To: kifer@cs.sunysb.edu
Cc: Dan Connolly <connolly@w3.org>, public-rule-workshop-discuss@w3.org, public-rule-workshop-discuss-request@w3.org
Message-ID: <OFBC04D7B6.480A5A64-ONC1257068.0039CAEE-C1257068.0042251E@agfa.com>

Michael Kifer wrote:
> Dan Connolly wrote:
>> 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.
>
> Hi Dan,
> Welcome to the discussion! Yes, it is very important to
> get to the bottom of it so that everybody will start
> speaking the same language.
>
> No, the above rule is nonmonotonic. If you add a color
> specification to that car then :car.auto:specification
> will now include a color specification and log:notIncludes
> will become false. Therefore 
>    :car auto:color auto:black
> will no longer be derived.

I'm aware of following sentence from
http://www.w3.org/2000/10/swap/doc/Reach

[[
Also, if we start to just loosely talk about defaults in
the sense of "if you don't already know a color", then
different agents will end up drawing different conclusions
from the same data, which is not a good foundation for a
scalable web.
]]

and believe that

<uri-of-document> log:semantics ?F.
?F log:notIncludes {set-of-triples}.

is a robust approach and is monotonic
(you cannot add things to ?F)
 
-- 
Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/
Received on Thursday, 25 August 2005 12:03:08 GMT

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