receiving an event subscription request from a subscriber, the event subscription request comprising a plurality of notified parties;

determining whether an event notification rule is satisfied for K-th time, and in a case where it is determined that the event notification rule is satisfied for K-th time, sending an event notification to at least one notified party in the plurality of notified parties, wherein sending the event notification in the case where it is determined that the event notification rule is satisfied for K-th time is denoted as initial notification, and K is a positive integer; and

after the initial notification is performed, determining whether the event notification rule is satisfied for P-th time, and in a case where it is determined that the event notification rule is satisfied for P-th time, sending an event notification to at least one notified party in the plurality of notified parties, wherein sending the event notification in the case where it is determined that the event notification rule is satisfied for P-th time is denoted as re-notification, and P is a positive integer,

wherein the initial notification and the re-notification are performed at different moments,

in a case that there are a plurality of notified parties notified in the initial notification, at least one of the plurality of notified parties notified in the initial notification is different from the at least one notified party notified in the re-notification,

in a case that there are a plurality of notified parties notified in the re-notification, at least one of the plurality of notified parties notified in the re-notification is different from the at least one notified party notified in the initial notification, and

in a case that there is only one notified party notified in the initial notification and there is only one notified party notified in the re-notification, the notified party notified in the initial notification is different from the notified party notified in the re-notification.