Re: [RIF] A Modest Proposal: Work Out Some Concrete Examples; Example-1: CHANGE-BABY-IF-WET rule

From: Michael Kifer <kifer@cs.sunysb.edu>
Subject: Re: [RIF] A Modest Proposal: Work Out Some Concrete Examples; Example-1: CHANGE-BABY-IF-WET rule 
Date: Wed, 01 Feb 2006 15:03:06 -0500

> Francois Bry <bry@ifi.lmu.de> wrote:
> >
> > I agree that RIF should have (1) a clear declarative semantics and (2) 
> > in addition support conveying *some* *limited* specifications of 
> > procedural semantics (eg backward chaining is intended because with 
> > forward chaining the considered rules would require to process all/too 
> > many nodes on the Web).
> 
> I disagree with that, especially with the statement that "with forward
> chaining the considered rules would require to process all/too many nodes
> on the Web".

+[some very large number]

What makes "forward chaining" a particularly bad method, even if you think of
forward chaining as a way to perform saturation?  Forward chaining (including
saturation, or not) works exceedingly well in some situations (and exceedingly
poorly in others).  Standard backward chaining has exactly the same
characteristics, by the way.  It all depends on the situation, and the
parameters used to control the chaining.

> This is all a matter for the query optimizer to resolve.

Well, it is all a matter for some piece of softare to resolve.  This may or may
not be something like a "query optimizer".

> > Back to RIF: I beleive RIF should give rise to express:
> > 
> > - logical formulas in a FOL style (preferably using a rich syntax)
> > - intended use of the formulas (eg deduction rule, integrity 
> > constraints, ontologies)
> > - intended negation (monotonic or non-monotonic)
> > - intended declarative semantics (eg Well Founded or Stable Model or FOL)
> > - intended truth valuations of all kinds (including discrete truth 
> > valuations such as eg true/false, true/unknown/false, 
> > known-tue/possibly-true/possibly-false/known-false as well as continous 
> > truth valuations such as [0..1] 0 meaining false, etc.)
> > - schemas (in the acception of RDFS) ie what is also called sorts in 
> > automated reasoning and logic (ie classes and sub-class relationships 
> > and the like)
> > - name (not procedural semantics!) of the rule engine the rules have 
> > been designed for.
> > - maybe further "properties".
> > 
> > Of course, RIF should make it possible that some of the above is not 
> > specified with a ruleset.
> 
> Amen to that (although I am not sure that we will want to handle all of
> that in the end).

Well this does sound like some sort of holy grail of formal representation (and
more).  I certainly don't want to spend time in RIF searching for a holy grail,
even if the search has desirable side-effects.

> 	--michael  

peter

Received on Wednesday, 1 February 2006 20:36:01 UTC