Re: [rules-users] CEP + prevent consequences from triggering multiple times?
Have you tried truth maintenance? (i.e. insertLogical)
rule "OverSpeedLimit" no-loop true
when
not SpeedingIndicator();
$minSpeed : Double(doubleValue > 100) from accumulate(
$speedingEvent : SpeedingEvent ($speed : speed)
over window:time( 30s )
from entry-point SpeedingStream,
min($speed)
);
then
insertLogical(new SpeedingIndicator());
end
Though I'm not sure this will work, because inserting the SpeedingIndicator negates
the first condition, probably causing the SpeedingIndicator to be retracted automatically.
:) But it's worth a try just to see if no-loop would override that somehow.
Apart from that, note that you can test the results of an accumulate in the returned
value. (The "Double(doubleValue > 100)" part.) YOu don't need the eval.
Also, where is the "state" object coming from? If it's a global, it's
not a good idea to use them in the conditions of your rules. Changes to them are not
tracked by the rete.
--- On Thu, 12/3/09, reverselogic <reverselogic(a)gmail.com> wrote:
From: reverselogic <reverselogic(a)gmail.com>
Subject: [rules-users] CEP + prevent consequences from triggering multiple times?
To: rules-users(a)lists.jboss.org
Date: Thursday, December 3, 2009, 12:41 PM
Hi,
I'm trying to write a rule in drools, which triggers once
some condition is
active for a specified time interval. For example, if a
vehicle is over a
speed limit (100 mph) for 30 seconds, I want to trigger an
action. However,
once this rule has fired, I don't want it to fire again
until the vehicle
has dropped below the speed limit (and gone over the limit
again). The only
way I've managed to model this is by defining two rules;
one for determining
when the vehicle is speeding and one for determining when
it is not speeding
and using a global object to track the state of the vehicle
(see rules
below).
rule "OverSpeedLimit" no-loop true
when
$minSpeed : Double() from accumulate(
$speedingEvent :
SpeedingEvent ($speed : speed)
over window:time( 30s )
from entry-point SpeedingStream,
min($speed)
);
eval ($minSpeed > 100.0 &&
!state.speeding)
then
state.speeding = true
end
rule "!OverSpeedLimit" no-loop true
when
$speedingEvent : SpeedingEvent()
from entry-point
SpeedingStream
eval ($speedingEvent.speed <= 100.0)
then
state.speeding = false
end
My questions is: Is there a better way to model the above
behaviour,
preferably as a single rule? The reason I ask is because I
believe it would
be too complicated for my users to define rules like this.
Ideally, I would
like to be able to create a DSL such as: "when Speed is
above X for Y
seconds then ..."
Any help greatly appreciated.
Thanks,
Paul
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