Supporting Hierarchy Of Groups (i.e., Groups of Groups)

Currently, groups are "flat", in the sense that they are made up of lists of members or queries, and there is no "OR" or similar mechanism to jon groups together, or to create "super-groups".

Right now, there's a serious discussion going on at Drupal.org on groups work for a new project: http://drupal.org/node/59082. Work I've already done will handle the "hierarchical groups" features of this work if it's possible to create "groups of groups", or if the "OR" operator can join groups.

This is a high value feature for many community or political applications, and is worth pushing forward.