Dear contributors, this simple rule should trigger only when a critical amount of particular events was detected, though it seems to accept any event of this type, disregarding the fact condition (e.g. there is no single event that matches "target == Long.MAX_VALUE"). The current behaviour results in an unconstrained type match: LocalizationEvent(): // annotation for external event class declare LocalizationEvent @role( event ) @duration( dur ) @timestamp( time ) end // triggers on *any* LocalizationEvent, regardless of fact condition rule "Detect crictial number of events" when accumulate( // there is no matching event $ev: LocalizationEvent(type == TYPE.LEFT, target == Long.MAX_VALUE, area == Long.MAX_VALUE) over window:time(30s) from entry-point "events/localization"; $n : count( $ev ); $n > 5 ) then System.out.println($n+" events detected" ); end The KB is configured for stream processing, the events are inserted in a chronological order and the session pseudo clock is advanced accordingly. Drools version in use is 5.4.0. Any suggestions are appreciated! Many thanks Jaro -- View this message in context: http://drools.46999.n3.nabble.com/Counting-events-fact-condition-not-eval... Sent from the Drools: User forum mailing list archive at Nabble.com.