Re: Fitting PR and RR into logical rules

> Sandro Hawke wrote:
> > I'm not suggesting building an automatic mechanism to tranform all PR
> > rulesets into FO rulesets.  Rather I'm suggesting that if we look at the
> > use cases for PR we'll see that semantically they fit nicely in with FO.
> >
> > Specifically, here's my strawman.   I propose the ECA/Reaction rule:
> >
> >     on Event
> >     when Condition
> >     then Action
> >
> > be treated semantically as the Horn rule (FOL implication):
> >
> >     if eventHappened(Event) and Condition
> >     then actionRequested(Action)
> >
> > and similarly for production rules (just drop the event part).
> >
> > This does not mean that an FOL theorem prover would be an effective way
> > to execute real-world ECA rule sets, but it does mean that any results
> > it was able to compute would be correct.  (That is, it supports the
> > Soundness requirement I've been advocating.)  I do expect that some easy
> > ECA rulesets would work with resolution-style reasoners using this
> > approach, but that's more a confirmation than a goal.  (This proposal
> > does not address the split in semantics between LP and FOL - that's a
> > separate question.)
> >
> > If you want to argue against this proposal, please just point to rules
> > from our use cases for which you think this approach will be bad and we
> > can look at an implementation sketch in detail.
> >
> >      -- Sandro
> >   
> 
> One first objectikon is the so-called "conflict resolution". The
> standard production / evewnt-condiotion-action rule pasradigm, ie the
> one people in the world knoiw about, is based on choosing one of the
> rule instance that could "fire" (as it is called).
> 
> Deduction rules are by no means based on such a choice.
> 
> This is a considerable difference that cannot be ignored.

What is conflict resolution good for?   Why do users want it?

I can imagine it's essential in rules where the action changes internal
system state.   My emerging hypothesis is that such rules will be part
of the 20-40% of the problem that Standard RIF will have to ignore.

Quoting from the Workshop Report [1], "Not only do [users] not need
complexity, but anything complex (such as prolog!) will drive them off."

You weren't there, but Mark Linehan gave a very convincing presentation
in which he claimed, speaking for IBM: 

       "In our experience, very simple business rules cover 60%, 80%,
       maybe 95% of the users." [2]

> One second objection is how rules are processed. Event queries have to
> be evaluated "event driven", while "conditions" have to be evaluated
> query driven.  
> ... for otherwise very poor implementation will be given ...

Sure -- but that's an implementation issue.  I'm not arguing that this
unified solution leads to an handy unified implementation; rather that
it gives us a simple unification of the semantics between ECA, PR, and
DR.

       -- Sandro


[1] http://www.w3.org/2004/12/rules-ws/report/#the-95
[2] http://www.w3.org/2004/12/rules-ws/report/minutes#ibm

Received on Tuesday, 6 June 2006 09:52:52 UTC