Package org.drools.mvel.evaluators

Class BeforeEvaluatorDefinition

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

The implementation of the 'before' evaluator definition.

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

Lets look at an example:

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

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

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

The temporal distance interval for the before 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, then 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 before[ -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 before[ -3m30s, -2m ] $eventB )
 $eventA : EventA( this before[ -2m, -3m30s ] $eventB )
See Also: