[rules-users] CEP + prevent consequences from triggering multiple times?

[Greg Barton]

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 at gmail.com> wrote:

> From: reverselogic <reverselogic at gmail.com>
> Subject: [rules-users] CEP + prevent consequences from triggering multiple times?
> To: rules-users at 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
> 
> 
> 
> 
> -- 
> View this message in context: http://n3.nabble.com/CEP-prevent-consequences-from-triggering-multiple-times-tp67424p67424.html
> Sent from the Drools - User mailing list archive at
> Nabble.com.
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