Hi, I have to create a set of rules that group facts together based on a dynamic criteria X basd on fact data. So I created a rule to create a first collection for the criteria X when no collection exist. I created a second rule to add a fact to an existing collection, but I cant get my head around how to create a rule that takes facts out of the collection if a fact is updated and no longer satisfies X. Note that the criteria X is a combination of 7-10 field equality. rule when f:Fact1(var1: a, var2:b) not FactCollection( a == var1, b == var2, fs:facts -> (fs.contains(f) == true) ) then ... assert(new FactCollection(f)); end rule when f:Fact1(var1: a) c:FactCollection( a == var1 ) then c.add(f); modify(c); modify(f); end rule when f:Fact1(id:id, type=UPDATE, var1: a) f2:Fact1(id == id, a == var1, b == var2) fs:FactCollection( not(a == var1, b == var2), fs:facts -> (fs.contains(f2) == true) then fs.remove(f2); modify(fs); end Since I dont want to create a rule for each combination of a != var1, b == var2, a == var1, b != var2 (I have 7-10 individual conditions), but I do want to check whether the collection contains f2 what else to do? any ideas?