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Re: PRD review, part 2

From: Michael Kifer <kifer@cs.sunysb.edu>
Date: Sat, 16 Feb 2008 03:06:58 -0500
To: Gary Hallmark <gary.hallmark@oracle.com>
Cc: W3C RIF WG <public-rif-wg@w3.org>
Message-ID: <6869.1203149218@cs.sunysb.edu>


Gary Hallmark wrote:
> 
> 2.2.
> 
> I find the semantics hard to understand.  The semantics in the simpler 
> case of no quantifiers (save for an enclosing forall) and only ground 
> uniterms in WM should be something fairly easily understood.  For example:

The semantics has not been specified, and there is nothing to understand :-)
As I said in my earlier message, the problems in this document are too
numerous and have much to do with the lack of rigor. 

> 3.
> 
> Many PR systems have "truth-maintenance".  This is sort of like a rule 
> head that gets asserted if the rule condition is true, but then gets 
> retracted should the rule condition later become false.  An action named 
> "Conclude" might capture this.

Right! I made the same point in my earlier message. When negation is
involved, it splits not only the logical rules into several different
streams, but also the semantics of the different PR languages diverge.
So, including it in the "core" of PR dialects is wrong.


> 4.1.
> 
> There should be some nontrivial intersection of PRD and BLD rules with 
> exactly the same syntax and semantics (even though the semantics is 
> written down differently, test cases should give the same answers).  
> Otherwise, I think we will have failed...

Horn gives the same semantics. Now, the question is how to massage that
into the PRD syntax. For instance, do we necessarily need "assert" in the
head of the PRD rules? Maybe this could be an option? In that case, we have a
common subset.



	--michael  
Received on Saturday, 16 February 2008 08:08:05 GMT

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