Drools - Accumulate logic - drools

Question

I need help in writing the accumulate logic for below requirement:
Requirement: Certain rules will provide the percentage to be applied for global value. Another set of rules should use the aggregate total percentage in determining the result.
For example: 0.75 is the global value passed as input(threshold).
Rule 1 might apply -10% of the fixed value ie. 0.75 - (0.75 * 0.10) = 0.675
Rule2 will apply + 20% off updated value. ie., 0.675 + (0.675 * 0.20) = 0.81
My global value is 0.75 (Threshold)
Using the below rules I am trying to applied the percentage applicable for a fixed value :
//class imports
global Double FIXED_THRESHOLD;
//Rules
rule "Prediction Rule_2"
lock-on-active true
no-loop true
salience (2)
when
LossInput (airBagDeployed == 'Y' , driveable == 'N')
result : RuleResult(predictedTotalsThreshold == 0)
then
insert(new ControlFact( -10.0 ) ); //Reduce -10% to global value 0.75 - 0.75* 0.10 = 0.675
System.err.println("New control fact added to working memory....");
end
rule "Prediction Rule_1"
lock-on-active true
no-loop true
salience (1)
when
LossInput (airBagDeployed == 'Y' , driveable == 'N', make == 'Honda' )
result : RuleResult(predictedTotalsThreshold == 0)
then
insert(new ControlFact( 20.0 ) ); // Add 20% to the updated aggregate (0.20 % of 0.675).
System.err.println("New control fact added to working memory....");
end
I tried the below accumulate logic but obviously it is wrong. It is applying only to fixed value always instead of the updated value.
rule "Aggregate All Threshold"
no-loop true
when
$aggregateTotalsThresholdPercentage : Number() from accumulate(
ControlFact( $totalsThreshold : totalsThresholdPercentage ),
sum( ( FIXED_THRESHOLD + ( FIXED_THRESHOLD * $totalsThreshold ) / 100 ) ) )
ruleResult: RuleResult(predictedTotalsThreshold == 0)
then
ruleResult.setPredictedTotalsThreshold($aggregateTotalsThresholdPercentage.doubleValue());
update(ruleResult);
end
POJO:
public class LossInput{
private String airBagDeployed;
private String driveable;
private String make;
}
public class ControlFact {
public double totalsThresholdPercentage;
}
public class RuleResult {
private double predictedTotalsThreshold;
}
//insert facts in working memory
kieSession.insert(lossInput);
kieSession.insert(ruleResult);
kieSession.setGlobal("FIXED_THRESHOLD", new Double(0.75));
kieSession.fireAllRules();
Please help on the accumulate logic to apply the updated value everytime when percentage threshold to be applied.

Answer 1

You cannot use accumulate/sum this way because you add the FIXED_THRESHOLD for each ControlFact.
Insert ControlFacts as you have in the "Prediction..." rules (without all the rule attributes). Use each ControlFact to update RuleResult's predictedTotalsThreshold. The "Aggregate" rule will fire repeatedly, and therefore you need to make sure to retract the used ControlFact.
rule "Aggregate All Threshold"
when
ControlFact( $ttp: totalsThresholdPercentage );
$res: RuleResult( $ptt: predictedTotalsThreshold)
then
double nt = $ptt + $ptt*$ttp/100;
modify( $res ){ setPredictedTotalsThreshold( $nt ) }
retract( $res );
end