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Re: Comments on * DRAFT * Rules Working Group Charter $Revision: 1.60 $

From: <jos.deroo@agfa.com>
Date: Thu, 25 Aug 2005 12:19:13 +0200
To: kifer@cs.sunysb.edu
Cc: public-rule-workshop-discuss@w3.org
Message-ID: <OF38699A27.DDB70733-ONC1257068.0037789E-C1257068.0038A99D@agfa.com>

>>>> [...]
>> >> 
>> >>> Allow me to set things straight please. The inference rules
>> >>> that are often (incorrectly) referred to as NAF ***always***
>> >>> have scope. I am not familiar with any notion of NAF that
>> >>> doesn't refer to a scope. Typically the scope is IMPLICIT,
>> >>> but it is ALWAYS WELL DEFINED. So, NAF is a form of SNAF
>> >>> where the scope is defined implicitly, but always rigorously.
>> >>> All Prolog systems that I am aware of are like that.
>> >>
>> >> Suppose that in my Prolog program I use lots of consult of
>> >> resources on the web and also lots of assert and retract all
>> >> conditioned by the state of the web, then how can you possibly
>> >> say that that scope in which I'm deriving evidence while using
>> >> negation as failure is ALWAYS WELL DEFINED??
>> >
>> > At any moment when NAF is computed the set of rules and facts
>> > is known to the inference engine. What is your problem?
>> It is indeed known internally to the engine, no doubt.
>> Would like to see that "ALWAYS WELL DEFINED" *outside*
>> the engine to support "proof supporting a conclusion".
> First, what you are talking about is way ahead of what W3C
> has in mind. Knowledge base dynamics is not even on the
> horizon as far as the current discussion is concerned.
> Second, what do you mean by "well defined outside the engine"?
> If your KB is dynamic then you can still provide explanations
> to proofs (if this is what you meant), but such things become
> more difficult, of course.

Yes, this is what I meant; agree now with your "well-defined"
I'm indeed not enough familiar with all literature and I will
try to catch up as much as possible :) (I did Prolog in
mid 80's and now again since last 5 years but have a gap
between 90 and 00) 

> If you want to determine the state of a dynamic KB at a
> particular point of execution ahead of time then it is
> undecidable for reasonably expressive languages (recursion
> is all you need for that).


Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/
Received on Thursday, 25 August 2005 10:19:44 UTC

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