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Re: Notes on 7/20 BLD draft

From: Michael Kifer <kifer@cs.sunysb.edu>
Date: Tue, 24 Jul 2007 07:14:11 -0400
To: Chris Welty <cawelty@gmail.com>
Cc: "Boley, Harold" <Harold.Boley@nrc-cnrc.gc.ca>, "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>
Message-ID: <15273.1185275651@cs.sunysb.edu>


> >> * It seems to me a cleaner syntax is to remove existentials from 
> >> conditions and unify all quantifiers outside the rule (as with 
> >> universal now), and add a restriction in horn that existentially 
> >> quantified vars cannot appear in the conclusion.
> > 
> > The RIF Basic Condition Language is meant to be reusable also
> > (in PR and) outside the context of any rule, stand-alone (e.g.
> > for queries and integrity checking), where existentials cannot
> > be rewritten as universals in the Example 3b.->3a. manner.
> 
> Oh, you misunderstood - I did not mean eliminate existentials from the 
> syntax entirely, I meant move them outside conditions into some sort 
> of wrapper or context (like, rules).  This would make, at least, the 
> rule syntax cleaner.

Unless I misunderstood you, what you are proposing is not sound in FOL:

Exists X foo <- bar(X)

is not the same as

foo <- Exists X bar(X).



	--michael  
Received on Tuesday, 24 July 2007 11:14:17 GMT

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