EVENT INFORMATION SERVER, CONTROL METHOD AND CONTROL PROGRAM

PROBLEM TO BE SOLVED: To reduce a processing time for reporting presence information showing a status of an event. SOLUTION: A presence server stores watcher information in a disk device in association with presentity information, and includes a cache for temporarily storing a part of the information stored in the disk device. When the watcher information corresponding to received presentity information is stored in the cache, the watcher information is obtained from the cache, while when not stored in the cache, the watcher information is obtained from the disk information, and presence information is transmitted. The timing to update the received presence information thereafter is predicted from the presence information, the predicted timing is compared with a preset threshold. When the predicted timing falls within the threshold, the presence server stores the presentity information and the watcher information in the cache. COPYRIGHT: (C)2009,JPO&INPIT