Consider these rules: rule "no Ax Or Ax 1" when EventA(id == "1") and Boolean( $v: booleanValue == true ) or (not EventA(id == "1")) and Boolean( $v: booleanValue == false ) then System.out.println( "#1: A(1) is " + $v ); end rule "no Ax Or Ax 2" when (EventA(id == "1") or not( EventA(id == "1") )) List( $size: size ) from collect( EventA(id == "1") ) then boolean v = $size > 0; System.out.println( "#2: A(1) is " + v ); end Rules #1 and #2 fire as expected while inserting lots of EventA(id=="1"), once for each new one. Rule #1 fires as expected after retracting the last inserted fact. Rule #2 does not, BUT if I split the rule manually in two, they both fire: ...when EventA(id == "1") List(... and ...when not( EventA(id == "1") ) List(... Using 5.1.1. -W