1. In a computer system that delivers notifications to a user, a method for controlling the delivery of the notifications, comprising: declaring a first condition that can be in at least first or second states; providing a first delivery instruction that is to be carried out for controlling the delivery of notifications when the first condition is determined to be in its first state; and receiving notifications from a plurality of sources and controlling the delivery of the notifications in accordance with the first delivery instruction when the first condition is determined to be in its first state.