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Re: Grammar presentation syntax FLD and BLD

From: Michael Kifer <kifer@cs.sunysb.edu>
Date: Fri, 29 Feb 2008 10:13:38 -0500
To: Jos de Bruijn <debruijn@inf.unibz.it>
Cc: RIF <public-rif-wg@w3.org>
Message-ID: <22027.1204298018@cs.sunysb.edu>


Jos wrote:
>
> >> Incidentally, I think there is a problem with the syntax for rules, as 
> >> specified in FLD.  Namely, a rule is an implication phi :- psi; no 
> >> quantification seems to be allowed. In the grammar below I also allowed 
> >> rules with universal quantification.
> > 
> > There are also quantified formulas. In FLD you can have arbitrary quantifiers.
> > I could have called phi :- psi a "Rule Implication" instead, but "Rule"
> > seemed shorter and acceptable.
> 
> I guess this means an FLD rule set is a set of formulas?

Yes, because FLD is supposed to cover a possible future FOL dialect,
disjunctive LP, and Lloyd-Topor extensions.

> > Note that the formal syntax uses "universal" for what BNF calls a "rule".
> > These universals correspond to "Implies" in BNF. Unfortunately, Implies is
> > not so good, if FLD is taken into the account, since FLD can have two kinds
> > of "implies": :- and <-. Currently, <- is not used in FLD, but it could be,
> > so it is better to avoid the confusion.
> 
> Actually, I was proposing to get rid of "Implies" in BNF, because I was 
> not convinced of its usefulness.
> 
> Could you actually point me out where the implication <- is defined in 
> FLD?  I could not find it.

I said that currently FLD *does not* use the classical implication
connective (->), but we might include it in the future (for instance, for
FOL and languages that support Lloyd-Topor extensions). For this reasons, I
avoided calling phi :- psi an "Implication" in the formal syntax of FLD
(not to be confused with the BNF of BLD, which used Implies).

So, ideally, to be compatible with FLD and to be extensible, it may be
necessary to call the top level nonterminals in BNF "Formula" or "FormulaSet".
I realize that for BLD the names "Rule" and "RuleSet" seem more
appropriate, but if we think about extensible BNF grammars then we might
need to be more general.


	regards
	  --michael  

> Best, Jos
> 
> > 
> > Proposals for better names would be appreciated.
> > 
> > 
> > 	--michael  
> 
> -- 
>                           debruijn@inf.unibz.it
> 
> Jos de Bruijn,        http://www.debruijn.net/
> ----------------------------------------------
> One man that has a mind and knows it can
> always beat ten men who haven't and don't.
>    -- George Bernard Shaw
> 
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> --------------ms050207030102090906040705--
> 
Received on Friday, 29 February 2008 15:14:17 GMT

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