Hi! I've detected some problems in my rules regarding event expiration but I can't understand why. Maybe someone with more experience could help me out. I think the example is quite simple: the application receives transactions. The lack of transactions for an hour should raise an alarm. If there's a transaction when the alarm is on, then the application should rearm, clear the alarm state and check for lack of transactions. The rules: package com.company.application; import com.company.application.Notifier; import com.company.application.Notification; import com.company.application.Transaction; dialect "java" # event which represents an alarm state declare NoTransactions @role( event ) dummy1: long end # event which represents the start of drools engine declare EngineStarted @role( event ) dummy2 : long end # event which represents the need to check for absence of transactions for the first hour declare CheckFirstTransaction @role( event ) @expire( 1h ) dummy3: long end # event which represents a Transaction declare Transaction @role( event ) @expires( 1h ) end # Notification System global Notifier notifier; rule "***start***" when not( EngineStarted() ) then insert( new EngineStarted() ); insert( new CheckFirstTransaction() ); end rule "***notrx_after_start***" when $engineStarted : EngineStarted() $checkFirstTransaction : CheckFirstTransaction() not( NoTransactions() ) not( Transaction( this after[0s,1h] $engineStarted ) from entry-point "incoming" ) then insert ( new NoTransactions() ); retract( $checkFirstTransaction ); notifier.send( new Notification( "ALARM" ) ); end rule "***notrx_after_trx***" when EngineStarted() not( NoTransactions() ) $transaction: Transaction() from entry-point "incoming" not( Transaction( this != $transaction, this after [0s,1h] $transaction ) from entry-point "incoming" ) then insert( new NoTransactions()); notifier.send( new Notification( "ALARM" ) ); end rule "***rearm***" when EngineStarted() $noTransactions : NoTransactions() $transaction: Transaction( this after $noTransactions ) from entry-point "incoming" then retract( $noTransactions ); notifier.send( new Notification( "REARM" ) ); end The unit test: kSession.fireAllRules(); // needed to detect lack of transactions in the first hour /* here, "***start***" rule fires => "EngineStarted" and "CheckFirstTransaction" inserted */ clock.advanceTime( 1, TimeUnit.HOURS ); /* here, "***notrx_after_start***" rule fires => "NoTransactions" inserted, "CheckFirstTransaction" retracted */ clock.advanceTime(10, TimeUnit.MINUTES ); entryPoint.insert( new Transaction() ); /* before inserting "Transaction" into EntryPoint, "NoTransactions" is retracted */ kSession.fireAllRules(); The problem: After inserting the last transaction, automatically the NoTransactions event is retracted. Debugging inside drools-core project, I've discovered that the event was retracted because expiration (WorkingMemoryReteExpireAction on actionQueue). I've also found some more explain how expiration events works, by Edison (http://drools-java-rules-engine.46999.n3.nabble.com/Events-are-not-automa...). That shed some light on *when* the event is retracted but I don't understand *why* it's retracted. Thanks In Advance! Vítor Mendonça Moreira Analista / Programador Direcção de Investigação e Desenvolvimento Rua Dr. Francisco Sá Carneiro, nº. 4 r/c esq. 2500 - 206 - Caldas da Rainha Tel: (+351) 262 832 196 Fax: (+351) 262 186 455 Web: www.makewise.pt <http://www.makewise.pt> Uma empresa: Grupo Sousa Pedro <http://www.sousapedro.com>