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RE: [RIF] Reaction to the proposal by Boley, Kifer et al --> ECA vs PR

From: Vincent, Paul D <PaulVincent@fairisaac.com>
Date: Wed, 3 May 2006 14:45:11 -0700
Message-ID: <B3636F07C8359844A9A2370C5EA08CCBE4467C@SRFMSGMB00.corp.fairisaac.com>
To: "Gerd Wagner" <wagnerg@tu-cottbus.de>, "Alex Kozlenkov" <alex.kozlenkov@betfair.com>, "Dave Reynolds" <der@hplb.hpl.hp.com>
Cc: <public-rif-wg@w3.org>

Gerd - I think you will find that many rule engine vendors provide
execution mechanisms for multiple rule types. In Blaze Advisor, for
example, we support:
- Production rules (with semantics for RETE and sequential)
- Event rules* (with semantics for either UI events or process events,
including pre- and post-event state consideration if desired)
- Functions / procedures

[* = Note that Event rules are a superset of what are often described as
ECA rules - effectively the "condition" is optional - and are only
called event rules because they predate the more common use of ECA
rules]

I agree that state change is a different (and necessarily runtime)
semantic to a state condition, but they are both attributes of state
(event or value). Indeed, it would be a mistake to assume rules about
events are solely about instantaneous actions based on some event
occurring: often event processing is about correlation, in which case
the event is reduced to a fact that some event has occurred at time t.
And of course, you are then back into regular, boring old production
rules! 

[And, of course, you are right that I tend to view everything through PR
spectacles!]

However, I would be interested to know what ECA-specific rule vendors
are present in RIF, and whether they have an agreed description for ECA.
As you know, we are planning an ECA metamodel in PRR as a non-normative
example of how PRR could be extended to include other rule types. 

Cheers,
Paul Vincent
...for Fair Isaac Blaze Advisor / W3C RIF

> -----Original Message-----
> From: Gerd Wagner [mailto:wagnerg@tu-cottbus.de]
> Sent: Wednesday, May 03, 2006 9:15 PM
> To: Vincent, Paul D; 'Alex Kozlenkov'; 'Dave Reynolds'
> Cc: public-rif-wg@w3.org
> Subject: RE: [RIF] Reaction to the proposal by Boley, Kifer et al -->
ECA
> vs PR
> 
> > Alex: just some views on ECA from a vendor in this space...
> 
> Paul, you mean from a production rule vendor's
> point of view, right :-?
> 
> > > various events, not just data changed.
> >
> > [PV>] Note that this is (mostly) an execution aspect. If I have an
ECA
> > rule that occurs on event A, it looks very similar to a PRule with a
> > condition of the type "event A occurred".
> 
> I guess, ECA rule vendors would not agree with your
> attempt to neglect the specific semantics of events.
> 
> It's not an execution aspect, it's a question of the
> right semantics. Normally, "condition" (in the sense
> of "logical condition") means "state condition", where
> "state" may refer to the state of a system, or to the
> "state of affairs".
> 
> Now, an event corresponds to a state change and is
> therefore a completely different kind of thing that
> cannot be subsumed under the concept of a state condition.
> A complex logical condition formula is formed with the
> help of logical connectives, while a complex event
> expression is formed with the help of a different set
> of (event composition) operators.
> 
> It's true that logical conditions and events are all
> mixed up in production rules. Semantically, this is
> a mess (and typically production rules do not have
> much support for event composition). But you may
> consider it a strength, making production rules
> a versatile programming paradigm (however, without
> a clear formal semantics).
> 
> -Gerd

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Received on Wednesday, 3 May 2006 21:49:46 GMT

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