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Re: On production rules and phase I&II

From: Peter F. Patel-Schneider <pfps@inf.unibz.it>
Date: Tue, 07 Mar 2006 18:10:02 -0500 (EST)
Message-Id: <20060307.181002.72678621.pfps@research.bell-labs.com>
To: frank.mccabe@us.fujitsu.com
Cc: public-rif-wg@w3.org

From: Frank McCabe <frank.mccabe@us.fujitsu.com>
Subject: On production rules and phase I&II
Date: Tue, 7 Mar 2006 14:56:37 -0800

> Part of the proposed plan is to partition the handling of production  
> rules across the phases, with phase I being the 'pure' subset of  
> production rules.
> The pure subset corresponding to an extremely small subset of horn  
> clause logic (no recursion!) and an extremely small subset of PR (no  
> modify or remove in the action part of the rule)

I don't understand where the "no recursion" comes from here.  Could you perhaps
point to evidence that recursion is not going to be part of phase I?  

> Quite apart from the fact that that to isolate this small subset of  
> PRs is to completely miss the point & approach of PRs, there is a  
> further technical issue.
> It is possible to map a rule of the form
> when A & B then assert C
> into a 'horn clause' of the form
> isTrue(C) <- A ^ B

Well, maybe, but wouldn't it be much better to just map it into 

	C <- A ^ B

> A point to bear in mind: to support chaining, it will be nec. to  
> conclude from
> isTrue(C)
> to
> C
> This appears to imply a Kripke-style possible world semantics.

Why?  Even if one was to utilize isTrue, then why would isTrue just be a truth
predicate, which does not require a Kripke-style semantics.

[ Some interesting issues having to do with retraction removed. ]

> Frank

Peter F. Patel-Schneider
Received on Tuesday, 7 March 2006 23:10:34 UTC

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