The not-so-immediate solution would be to use queries, for example something along the following lines: declare Node id : String children : Node[] value : Integer end rule "Init" when then Node n1 = new Node( "l1", new Node[] {}, 10 ); Node n2 = new Node( "l2", new Node[] {}, 7 ); Node n3 = new Node( "l3", new Node[] {}, 9 ); Node x1 = new Node( "x1", new Node[] { n1, n2 }, -1 ); Node x2 = new Node( "x2", new Node[] { n3 }, -2 ); Node rt = new Node( "00", new Node[] { x1, x2 }, -3 ); insert( n1 ); insert( n2 ); insert( n3 ); insert( x1 ); insert( x2 ); insert( rt ); end query score( Node $node, Integer $score ) // either the node is a leaf, so just return its value $node := Node( children.length == 0, $score := value ) or ( // or it is not, so let's pick the children $node := Node( $children : children, $sz : children.length > 0, $val : value ) and accumulate ( // for each child... $child : Node( this memberOf $children ) and // ... calculate the partial child's score recursively score( $child, $x ; ), // sum all the partial scores $tot : sum( $x ) ) and // add the local parent value and return $score := Integer() from $tot.intValue() + $val ) end rule "Check" when $n : Node() score( $n, $x ; ) then System.out.println( "Query-ed value from node " + $n + " >>> " + $x ); end In the last rule, you can replace $x with a literal (also remove it from the printout) : score( $n, 20 ; ) and the rule will fire only for those nodes whose "deep sum" is 20 On 02/28/2013 01:20 PM, Wolfgang Laun wrote: