[rules-users] Ordered lists in drl

I am trying to write a rule via the guided rule editor and (again!!) I am really struggling. The following is a simplified explanation of my scenario: I have a model where there is one 'Supermarket' object which has a list of integers 'locationID'. Elsewhere I have another list of 'Place' objects, each of which has an integer locationReference. Something like this.... <Supermarket name = 'asda'> <LocationID>21</LocationID> <LocationID>18</LocationID> <LocationID>19</LocationID> </Supermarket> <Places> <Place> <LocationReference>21</LocationReference> </Place> <Place> <LocationReference>18</LocationReference> </Place> <Place> <LocationReference>19</LocationReference> </Place> </Places> I need to write a rule that fires when the *order* of locationIDs does not match the order of the locationReferences. So the above example would be fine but the model below would not... <Supermarket name = 'asda'> <LocationID>18</LocationID> <LocationID>21</LocationID> <LocationID>19</LocationID> </Supermarket> <Places> <Place> <LocationReference>21</LocationReference> </Place> <Place> <LocationReference>18</LocationReference> </Place> <Place> <LocationReference>19</LocationReference> </Place> </Places> I know that drools does not consider the order of facts in the model, however since both facts are java.util.Lists I wonder if it possible to compare the elements at position 0, 1, 2 etc. I am afraid my drl skills are really not up to scratch. Any thoughts? -- View this message in context: http://drools.46999.n3.nabble.com/Ordered-lists-in-drl-tp3519453p3519453.... Sent from the Drools: User forum mailing list archive at Nabble.com.