Thanks for the quick reply W!! I think that was the nudge I needed. It seems like as long as I keep my timer interval shorter than the sliding window interval this should work. This rule passed my simple tests: *import drools.tests.MyEvent import java.util.List declare MyEvent @role(event) end rule "Grouped Events" timer( int: 500ms ) when $list : List() from collect ( MyEvent() over window:time(2s) ) then for( Object myEvent : $list ) { System.out.println( System.currentTimeMillis() + "ms: event group contains: " + myEvent.toString() ); } end* Please let me know if there's a danger with this approach or if there's a better way to do it. And thanks again! - Ladd -- View this message in context: http://drools.46999.n3.nabble.com/How-to-batch-high-freq-events-before-se... Sent from the Drools: User forum mailing list archive at Nabble.com.

I see what you mean about potentially catching events multiple times. Not good. And I can't retract them since other rules may be written to catch those same events. Marking each event would be possible but could get complicated for the same reason - multiple rules may be interested in them and would each need to mark them. Using a repeat interval for the timer does seem necessary alright. I like your singleton fact solution. I implemented this by having a "fire only once" rule create the list, a second rule looks for events matching the desired criteria and appends to the list, and a third rule uses the timer to look for the list, process its contents, and then clear those contents. I wanted to do it purely with DRL so I declared the list like this: *declare TimeBatchList name : String list : List end* Since I might have multiple "batching" rules like this, I need each one to have their own event batch/list. The name field keeps them unique (probably should change this to something like "id"). Seems to work. Thanks! - Ladd -- View this message in context: http://drools.46999.n3.nabble.com/How-to-batch-high-freq-events-before-se... Sent from the Drools: User forum mailing list archive at Nabble.com.