Package org.drools.mvel.evaluators

Class StartsEvaluatorDefinition

java.lang.Object
org.drools.mvel.evaluators.StartsEvaluatorDefinition
All Implemented Interfaces:
Externalizable, Serializable, EvaluatorDefinition, EvaluatorDefinition
public class StartsEvaluatorDefinition extends Object implements EvaluatorDefinition

The implementation of the starts evaluator definition.

The starts evaluator correlates two events and matches when the current event's end timestamp happens before the correlated event's end timestamp, but both start timestamps occur at the same time.

Lets look at an example:

$eventA : EventA( this starts $eventB )

The previous pattern will match if and only if the $eventA finishes before $eventB finishes and starts at the same time $eventB starts. In other words:

 
 $eventA.startTimestamp == $eventB.startTimestamp &&
 $eventA.endTimestamp < $eventB.endTimestamp

The starts evaluator accepts one optional parameter. If it is defined, it determines the maximum distance between the start timestamp of both events in order for the operator to match. Example:

$eventA : EventA( this starts[ 5s ] $eventB )
Will match if and only if: 
 
 abs( $eventA.startTimestamp - $eventB.startTimestamp ) <= 5s &&
 $eventA.endTimestamp < $eventB.endTimestamp

NOTE: it makes no sense to use a negative interval value for the parameter and the engine will raise an exception if that happens.

See Also: