Re: [rules-users] sliding window combination ?

Conceptually it's quite simple. Consider a loop int sum( int[] array ) i = 0; // init for( int a: array ){ i += a; // action } return i; // result Drools does the loop, calling your callbacks providing the appropriate context from the scope of the ___ in the accumulate( _____________________ , You could look at the implementations of the built-in accumulate functions, and you'll see the same callbacks as methods of the function provider class. Just for fun: You can also use: import java.util.Set; import java.util.HashMap; rule countById when $set: Set() from accumulate( Request( $id: id ), init( HashMap id2count = new HashMap() ), action( Integer i = (Integer)id2count.get( $id ); if( i == null ) i = 0; i++; id2count.put( $id, i ); ) reverse( Integer i = (Integer)id2count.get( $id ); i--; id2count.put( $id, i ); ) result( id2count.entrySet() ) ) java.util.Map.Entry( $id: key, $count: value > 1 ) from $set then System.out.println( "Id " + $id + ": " + $count ); end Don't worry - I wanted to research this for some time; never had an opportunity ;-) -W On 7 July 2011 17:18, Andre <morpheusandre(a)web.de&gt; wrote: