84.3. Metadata tags for events
The decision engine uses the following metadata tags for events that are inserted into the working memory of the decision engine. You can change the default metadata tag values in your Java class or DRL rule file as needed.
The examples in this section that refer to the VoiceCall
class assume that the sample application domain model includes the following class details:
VoiceCall fact class in an example Telecom domain model
public class VoiceCall { private String originNumber; private String destinationNumber; private Date callDateTime; private long callDuration; // in milliseconds // Constructors, getters, and setters }
- @role
This tag determines whether a given fact type is handled as a regular fact or an event in the decision engine during complex event processing.
Default parameter:
fact
Supported parameters:
fact
,event
@role( fact | event )
Example: Declare VoiceCall as event type
declare VoiceCall @role( event ) end
- @timestamp
This tag is automatically assigned to every event in the decision engine. By default, the time is provided by the session clock and assigned to the event when it is inserted into the working memory of the decision engine. You can specify a custom time stamp attribute instead of the default time stamp added by the session clock.
Default parameter: The time added by the decision engine session clock
Supported parameters: Session clock time or custom time stamp attribute
@timestamp( <attributeName> )
Example: Declare VoiceCall timestamp attribute
declare VoiceCall @role( event ) @timestamp( callDateTime ) end
- @duration
This tag determines the duration time for events in the decision engine. Events can be interval-based events or point-in-time events. Interval-based events have a duration time and persist in the working memory of the decision engine until their duration time has lapsed. Point-in-time events have no duration and are essentially interval-based events with a duration of zero. By default, every event in the decision engine has a duration of zero. You can specify a custom duration attribute instead of the default.
Default parameter: Null (zero)
Supported parameters: Custom duration attribute
@duration( <attributeName> )
Example: Declare VoiceCall duration attribute
declare VoiceCall @role( event ) @timestamp( callDateTime ) @duration( callDuration ) end
- @expires
This tag determines the time duration before an event expires in the working memory of the decision engine. By default, an event expires when the event can no longer match and activate any of the current rules. You can define an amount of time after which an event should expire. This tag definition also overrides the implicit expiration offset calculated from temporal constraints and sliding windows in the KIE base. This tag is available only when the decision engine is running in stream mode.
Default parameter: Null (event expires after event can no longer match and activate rules)
Supported parameters: Custom
timeOffset
attribute in the format[#d][#h][#m][#s][[ms]]
@expires( <timeOffset> )
Example: Declare expiration offset for VoiceCall events
declare VoiceCall @role( event ) @timestamp( callDateTime ) @duration( callDuration ) @expires( 1h35m ) end