[rules-users] Rule using accumulate

Hi guys, I'm new to drools, and i'm trying to build a small prototype. I have 2 entities in my model: Offers and Bids. Both have a size (and a price). I need a rule that matches a single Bid with multiple Offers adding up in size to the Bid size. Matched Offers have to be sorted by (increasing) insertion time . I have managed to write a rule using 'accumulate', but i feel it's not too efficient, since i have to match every Offer in the working memory with the right price, sort them and then pick the first n ones. Here's the rule: rule "Match Bids" when $b : Bid($s:size, $p:price) $i : OfferAccumulator(acumSize >= $s) from accumulate ( $o:Offer(price<=$p) , init(OfferAccumulator accum = new OfferAccumulator($s); ), action( accum.add($o);), reverse ( accum.remove($o);), result( accum )) then System.out.println( "Matched Bid:" + $b + "," + $i.getOffers()); end and here's OfferAccumulator: public class OfferAccumulator { private int sizeLimit=0; private int accumSize=0; Set<Offer> offers = new TreeSet<Offer>(); public OfferAccumulator(int sizeLimit) { this.sizeLimit = sizeLimit; } public void add(Offer op) { accumSize+=op.getSize(); offers.add(op); } public void remove(Offer op) { if (offers.remove(op)) { accumSize-=op.getSize(); } } public List<Offer> getOffers() { List<Offer> ret = new ArrayList<Offer>(); int accum=0; Iterator<Offer> it = offers.iterator(); while (it.hasNext() && acum<sizeLimit) { Offer offer = it.next(); accum+=offer.getSize(); ret.add(offer); } return ret; } } Can you think of a more efficient way of achieving the same result? Is there a way of controlling the order in which facts are feeded to the accumulator? Thanks in advance! Andres