On 04/08/2010 09:34, Wolfgang Laun wrote: Filter is the result of the agenda-filter causing the activation to cancel: if ( filter == null || filter.accept( item ) ) { // fire it fireActivation( item ); result = true; } else { // otherwise cancel it and try the next final EventSupport eventsupport = (EventSupport) this.workingMemory; eventsupport.getAgendaEventSupport().fireActivationCancelled( item, this.workingMemory, ActivationCancelledCause.FILTER ); tryagain = true; } WME_MODIFY is the result of any wme action that causes an activation to be cancelled. CLEAR is the result of a forced cancellation of an activation, either be explicitely calling clear or removing a rule. I agree we could probably split that out and have a KB_MODIFY, so that if the activation is cancelled as a result the rule being removed we get a different event. Mark