Zones

A zone is a collection of rooms.  Every room must exist in a zone.  A room cannot exist in more than one zone.  A zone is defined by a unique name and has no other properties.  A zone is not created by itself.  During the room creation, a zone is specified.  If that zone does not exist, then it is created.

Users joined to a room in a zone have access to the list of rooms in that zone.