Hello I switched recently from Drools 5.5.0 to Drools 6.0.0.Beta3 and some of my rule tests failed because Drools started doing weird things. I've isolated the problem and I figured out that it has to do with the combination of "accumulate" and "collect" conditions in the same rule. See this example here: > import java.util.ArrayList > > declare Item > code: int > price: int > present: boolean > end > > rule "Init" > when > then > insert(new Item(1,40,false)); > insert(new Item(2,40,false)); > insert(new Item(3,40,false)); > insert(new Item(4,40,false)); > end > > rule "CollectAndAccumulateRule" > when > //At least two items that aren't presents > objList: ArrayList(size>=2) from collect( Item(present==false)) > //Total price bigger than 100 > price: Number(intValue>=100) from accumulate( Item($w:price, > present==false), sum($w)) > then > > System.out.println("Sum: "+price); > System.out.println("Items size: "+objList.size()); > > //Look for the minor price item > Item min = null; > for(Object obj: objList){ > if (min!=null){ > min = (min.getPrice()>((Item)obj).getPrice())?(Item)obj:min; > } > else { > min = (Item)obj; > } > } > > //And make it a present > if (min!=null){ > modify(min){setPresent(true)}; > } > end It gets a list of items, and when exist at least two of them and the sum of its prices is bigger than 100, it makes a present of the cheapest one. For this, items have a "present" flag that gets activated when it becomes a present. Also, this flag is part of both "collect" and "accumulate" conditions, for the rule not to loop over already "presented" items. So, having 4 items with price 40 each (rule "Init" insert them), expected result is to have 2 presents of price 40. Rule "CollectAndAccumulateRule" gets executed two times and loop stops when there are just two remaining items, with sum 80 (<100). Expected output would be: Sum: 160.0 Items size: 4 Sum: 120.0 Items size: 3 This works fine in Drools 5.5.0, but not in 6.0.0.Beta3. In the latter rule "CollectAndAccumulateRule" gets called 3 times, and output is like this: Sum: 160.0 Items size: 4 Sum: 120.0 Items size: 4 Sum: 120.0 Items size: 3 Is there some overall change in 6.0.0.Beta3 that affects this kind of rules or conditions? Or could this be an issue? Furthermore, including this kind of rules in a package along with other no-conflictive rules, it makes the hole package start behaving unexpectedly. I guess it has to do with the way of the Rete tree is bulided when this kind of rules are present. Note: I know there are alternatives and workwarounds to the scenario shown here (like merging both conditions into a single "accumulate"). Nevertheless the aim of this post is just to try to determinate wheter this must be considered an issue or not Regards, -- Alvaro