[rules-users] how to do things like "distinct"?

Hi all, I have the following problem. Let's say, I have a class Number3(), with three fields a, b, and c. I have the following rule: rule "test3" when Number3($a: a, $b: b) $minvalue: Number() from accumulate(Number3(a == $a, b == $b, $c: c), min($c)) then System.out.println($a + " " + $b + " " + $minvalue); end Say, I have four objects (1,2,3), (1,2,4), (1,3,4), (1,3,5). The result shows four lines: 1 3 4.0 1 3 4.0 1 2 3.0 1 2 3.0 But I want the output to be: 1 3 4.0 1 2 3.0 meaning that for each unique pair of a and b, I want the rule to fire only once. Is this doable? Thanks. -Simon