Package org.drools.mvel.evaluators

Class AfterEvaluatorDefinition

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

The implementation of the 'after' evaluator definition.

The after evaluator correlates two events and matches when the temporal distance from the current event to the event being correlated belongs to the distance range declared for the operator.

Lets look at an example:

$eventA : EventA( this after[ 3m30s, 4m ] $eventB )

The previous pattern will match if and only if the temporal distance between the time when $eventB finished and the time when $eventA started is between ( 3 minutes and 30 seconds ) and ( 4 minutes ). In other words:

 3m30s <= $eventA.startTimestamp - $eventB.endTimeStamp <= 4m

The temporal distance interval for the after operator is optional:

  • If two values are defined (like in the example below), the interval starts on the first value and finishes on the second.
  • If only one value is defined, the interval starts on the value and finishes on the positive infinity.
  • If no value is defined, it is assumed that the initial value is 1ms and the final value is the positive infinity.

NOTE: it is allowed to define negative distances for this operator. Example:

$eventA : EventA( this after[ -3m30s, -2m ] $eventB )

NOTE: if the initial value is greater than the finish value, the engine automatically reverse them, as there is no reason to have the initial value greater than the finish value. Example: the following two patterns are considered to have the same semantics:

 $eventA : EventA( this after[ -3m30s, -2m ] $eventB )
 $eventA : EventA( this after[ -2m, -3m30s ] $eventB )
See Also: