When the status of a client X is changed to a status i, a group management unit generates a group agent Xi, corresponding to the status i and registers the generated group agent in the server S, and the presence issuing unit issues the status i and the identifier of the group agent Xi. Initially, a member...http://www.google.com/patents/US20050216565?utm_source=gb-gplus-sharePatent US20050216565 - Group communication system based on presence information and client device
