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Re: log:notIncludes (conclusion?)

From: Michael Kifer <kifer@cs.sunysb.edu>
Date: Sat, 27 Aug 2005 21:49:11 -0400
To: Sandro Hawke <sandro@w3.org>
Cc: public-rule-workshop-discuss@w3.org
Message-Id: <20050828014911.01EFFCB5D3@kiferserv.kiferhome.com>


> 
> > Since cwm, Flora-2, Prolog, etc., are real practical languages, it
> > seems a clear indication that nonmonotonicity is an important
> > feature of a web rule language.
> 
> Let me put the definition of monotonicity into the unix command line:
> 
>   bash$ cwm a --think > deductive_closure_of_a
>   bash$ cwm a b --think > deductive_closure_of_a_b
> 
> Is there any file "b" such that deductive_closure_of_a contains a
> triple which is missing from deductive_closure_of_a_b?  Maybe there
> are formatting options to cwm which would let me ask that question
> using diff and grep. :-)
> 
> My guess is that there is such a "b", but it uses some hairy kludge
> feature that should be avoided (accordning to N3/cwm's designer).
> 
> Why do people want non-mon?    For defaults, yes?    Anything else?

Defaults is one. The other reason is that it is impractical (and often
infeasible) to specify all the necessary negative facts. This is the main
reason why NAF is used in databases. In fact, even in LP I think the more
common use of NAF is due to that second reason.



	--michael 
Received on Sunday, 28 August 2005 01:49:15 GMT

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