[rules-users] problem in sliding window

hi, i have a rule file as follows: declare Event @role( event ) end declare window Ticks Event() over window:time(1m ) end rule "More than 5 file added events" when $p: RuleContext() Number(intValue > 4) from accumulate( $e :Event (name == "new file added") from window Ticks, count($e) ) then Event event = new Event("too many files added last minute",$p.getOldContext().getParent(),new Date()); event.display(); end this rule gets fired only if i add more than 4 files all at once.. say if i add first 2 files within the first 10 seconds, next two files after the 20th second and next two files after 40th second, this rule is not getting fired.. ( there are 6 file added events in the window over past 1 min and the rule should have got fired ). what is the problem with the current rules and how can i modify it to meet my requirement? Thanks.