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RE: BLD: two issues with the BNF

From: Boley, Harold <Harold.Boley@nrc-cnrc.gc.ca>
Date: Fri, 11 Jul 2008 12:44:47 -0400
Message-ID: <E4D07AB09F5F044299333C8D0FEB45E904FFE24A@nrccenexb1.nrc.ca>
To: "Jos de Bruijn" <debruijn@inf.unibz.it>, <kifer@cs.sunysb.edu>
Cc: "RIF" <public-rif-wg@w3.org>

We say
If a CLAUSE in the RULE production has a free (non-quantified) variable,
it must occur in the Var+ sequence.


-----Original Message-----
From: public-rif-wg-request@w3.org [mailto:public-rif-wg-request@w3.org]
On Behalf Of Jos de Bruijn
Sent: July 11, 2008 1:38 PM
To: kifer@cs.sunysb.edu
Subject: Re: BLD: two issues with the BNF

Michael Kifer wrote:
> On Fri, 11 Jul 2008 09:29:54 +0200
> Jos de Bruijn <debruijn@inf.unibz.it> wrote:
>>>> The second issue is not an error, but it can be considered
>>>> (the BNF is too liberal): in the presentation syntax, rules are 
>>>> quantified rule implications.  So, an atomic formula is not a rule
>>>> may thus not be directly included in a group.  According to the
BNF, an 
>>>> atomic formula can be considered a rule; this is misleading.
>>> There was a mistake in the math syntax. Groups should also allow
>>> formulas. Fixed.
>> One more thing: atomic formulas can also contain variables.  I guess 
>> that such non-ground atomic formulas should not be allowed in groups?
> I see no reasons why such formulas should be disallowed. They are
allowed as part of the KB, so why disallow them in groups?

I thought all variables in BLD need to be explicitly quantified?

Jos de Bruijn            debruijn@inf.unibz.it
+390471016224         http://www.debruijn.net/
If knowledge can create problems, it is not
through ignorance that we can solve them.
   - Isaac Asimov
Received on Friday, 11 July 2008 16:45:30 UTC

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