What I'd like us to achieve going forward (ideally in Snow Leopard) with regards to our uses of groups in iCal Server. 1- It's OK for location and resource GUIDs to be members of groups. It's not exactly normal, but it's valid and OK, so let's not worry about that. So for the "enabled for calendaring" group, feel free to throw these objects into the group. 2- We need to limit our use of groups to "is X a member of Y", which is an operation we can make against DS very quickly and very frequently. We needn't cache this, on the expectation that it should be fast enough. 3- Which means we need to get rid of cases where we try to enumerate all members of a group, or the groups a principal is a member of. This one is tough due to the current delegate model. It means the DAV:group-memberships and DAV:groups should generally be deprecated. I think that's doable for principals other than the delegate sub-principals without breaking current functionality, and for delegate sub-principals, we can keep flattened lists cached. If we do this, we should be able to do all group membership checks via DS and without needing an in-memory cache. -wsv