[rules-users] Accumulate / collect

Hi all, There is something I can't express using "collect" or "accumulate" and I would like to have your opinion. Let's imagine I have the following types : # a country type * declare Country name : String end * # a city type holding a reference to its country * declare City name : String country : Country end * Let's imagine I have all Country and City objects into the working memory. I want to get the set of Countries corresponding to Cities whose name starts with "X". I have the impression that I need a kind of (nonexistent right?) "collect" syntax that would look like the "accumulate" syntax (a kind of "anonymous" accumulate function): # meaning I want to collect $country objects and not City objects $countries : HashSet() from collect (City($name matches "X.*", $country : country)*, $country*) Or a home made accumulate function that builds a set of countries: # custom "buildset" accumulate function $countries : HashSet() from accumulate (City($name matches "X.*", $country : country), *buildset*($country)) Do you see any other (possibly out of the box) solution? Many thanks in advance for your answers, Best regards, Bruno.