So, if I get you right, I have to, for example, store some kind of time stamp in my event object and compare it? My definition of "previous" simply depended on the order, the objects were inserted into the working memory. -- View this message in context: http://drools.46999.n3.nabble.com/Get-previous-fact-from-working-memory-t... Sent from the Drools: User forum mailing list archive at Nabble.com.

Thank you very much. I'll try that. But there's another small problem I've just faced. I'm trying to insert a new Event object into the working memory. I can do that with but results in What am I doing wrong? -- View this message in context: http://drools.46999.n3.nabble.com/Get-previous-fact-from-working-memory-t... Sent from the Drools: User forum mailing list archive at Nabble.com.

No need to store a explicit timestamp, drools will do that for you. Your first option is a rule like this : rule "check_agains_last" when $e1 : EVENT1() $e2 : EVENT2(this before $e1) not EVENT2(this after $e2) then ... end Your second option is to implement a WorkingMemoryEventListener <http://docs.jboss.org/jbpm/v5.1/javadocs/org/drools/event/rule/WorkingMem...;, and implement the objectInserted method to store the last events inserted (a simple 2 sized rolling stack will do the job), and another that return the "previous" inserted Event object (the second element of your stack). this leads to a rule like this : rule "check_agains_last" when $e1 : EVENT1() eval (PreviousEventListener.getPreviousEvent() instanceof EVENT2) then ... end But in this last solution, you may fall into problem if two events are inserted in seom other thread while the rules are processed. In fact, I think you need "the event before another event", and not "the previous of the last one" (the "last one" may be not the one matched in your rule). Mays be your listener can be used to set, in a new event that is inserted, the reference to the last one inserted, something like that: class PreviousEventListener implements WorkingMemoryEventListener <http://docs.jboss.org/jbpm/v5.1/javadocs/org/drools/event/rule/WorkingMem... { private Object lastInserted; public void objectInserted (|ObjectInsertedEvent <http://docs.jboss.org/jbpm/v5.1/javadocs/org/drools/event/rule/ObjectInse... event)| { event.getObject().setLastEvent( lastInserted ); // check class before of course ... lastInserted = event.getObject(); } } rule "check_agains_last" when $e1 : EVENT1(...) $e2 : EVENT2(...) from $e1.getLastEvent() then ... end Le 06/10/2011 11:06, tungl a écrit : -- Vincent LEGENDRE /Consultant Sénior/ EURODECISION 9A rue de la Porte de Buc 78000 VERSAILLES Tél. : +33 (0)1 39 07 12 40 Direct : +33 (0)1 39 07 26 16 www.eurodecision.com EURODECISION <http://www.eurodecision.com/><http://www.eurodecision.com/>

This is handled by simply using the "before" temporal operator: $e1: Event1() $e2: Event2( this before $e1 ) -W On 6 October 2011 19:09, tungl <martin(a)seafoid.org&gt; wrote: