Hello, I am trying to achieve something like a SQL statement equivalent of: SELECT r.property1 AS p1, r.property2 AS p2, SOME_CALCULATION(r.property3) AS p3 FROM right AS r GROUP BY p2, p3 I am not sure if this is valid SQL since I am grouping by a calculated value, but that aside. I am asserting the Rights objects into the working memory and then would like to execute a rule on the objects based on a grouping of objects. The first property is directly accessible from the object right.getProperty2() but the second property is only accessible through a lookup MyClass.staticMethod(right.getProperty3()). As far as I have it the rule should make use of something like collect or accumulate but I do not know how to achieve this without also asserting the properties objects into the memory as well. And even if I assert the properties objects into the working memory I do not know how to group by the second property. rule "Calculate something" no-loop when $rights: ArrayList( ) from collect( Right( ) ); then // execute rule end Could you please give me some assistance? Regards Juan "Employees of Lonmin Platinum ("Lonplats") are not authorised to conclude electronic transactions or to enter into electronic agreements on behalf of Lonplats. Any electronic signature (other than an advanced electronic signature as defined in the Electronic Communications and Transactions Act of 2003) added to a data message (such as an email or an attachment to an (email) ostensibly on behalf of Lonplats by a Lonplats employee shall not be legally binding on Lonplats and Lonplats shall incur no liability of any nature whatsoever, directly or indirectly, arising from such act on the part of it's employee. It is further recorded that nothing (other than an advanced electronic signature) inserted into any data message emanating from Lonplats shall be construed as constituting an electronic signature"