Patent ID: 8484337

Claim:
A presence communication system for executing service after presence is carried out to check status of a target of communication before initiation of communication, comprising: a presence server having a group identifier as an identifier which is used to collectively look up a group of multiple pieces of presence information provided by multiple presence information providers who have agreed to a use policy, the presence server aggregating and storing the presence information under the group identifier and delivering the presence information requested to the group identifier; presentities which have agreed to the use policy of the multiple pieces of the presence information, as presence information-providing clients, to provide the presence server with presence information targeted to the group identifier; and watchers which have agreed to the use policy of the multiple pieces of the presence information, as presence information-requesting clients, to request the group identifier for the presence information provided by the presentities, and receive the presence information delivered from the presence server, at least one of the watchers forming a single group assigned the group identifier with the presentities, wherein the presence server sets a plurality of different group identifiers, the presentities provide the presence information to the respective different group identifiers, and the presentities each have a function of selecting one of the group identifiers and determine, with respect to the presence server, provision/non-provision or notification interval of the presence information, based on content of the presence information and a provision policy according to which the presence information is provided to the group identifiers; wherein the presentities included in the group transmit the presence information only once to the presence server while specifying the group identifier, and when the presence information is requested from the watchers, the presence server delivers the multiple pieces of presence information collectively to the watchers included in the single group; wherein the presence information stored under lowest-level group identifiers is aggregated successively to higher levels of a hierarchical structure such that all of the presence information is aggregated and stored under a highest-level group identifier; wherein the presence server has a plurality of group identifiers arranged in the hierarchical structure, and the presence server successively curtails the presence information as the presence information is aggregated from lower to higher levels of the hierarchical structure such that higher-level group identifiers hold smaller amounts of information; and wherein the presence server changes a delivery policy in accordance with the presence information of a key member and delivers in real time the presence information of members whose presence information is the same as that of the key member and delivers at intervals the presence information of the other members.