A method for handling subscriptions from a subscriber node to changes in data relating to a user held at a database node in a telecommunications system, the method comprising: at the subscriber node: preparing a subscribe message comprising: first information identifying first data which the subscriber node wishes to receive in a notification message in response to a change to the first data; second information identifying second data which the subscriber node wishes to receive with such a notification message; third information, different to the first information, specifying a condition to be fulfilled in relation to third data before such a notification message is sent; and fourth information specifying whether the subscriber node wishes to receive with such a notification message a version of the first data prior to the change; the first, second and third data each relating to the user and being held at the database node; and sending the subscribe message towards the database node; and at the database node: receiving the subscribe message sent from the subscriber node, the subscribe message comprising the first, second, third and fourth information; detecting a change to the first data identified by the received first information; in response to the detecting of such a change, and if it is determined that the condition specified in the received third information has been fulfilled, sending one or more notification messages towards the subscriber node, the notifcation message or messages comprising: the first data following the detected change; the second data specified by the received second information; and a version of the first data prior to the detected change. at the subscriber node: preparing a subscribe message comprising: first information identifying first data which the subscriber node wishes to receive in a notification message in response to a change to the first data; second information identifying second data which the subscriber node wishes to receive with such a notification message; third information, different to the first information, specifying a condition to be fulfilled in relation to third data before such a notification message is sent; and fourth information specifying whether the subscriber node wishes to receive with such a notification message a version of the first data prior to the change; the first, second and third data each relating to the user and being held at the database node; and sending the subscribe message towards the database node; preparing a subscribe message comprising: first information identifying first data which the subscriber node wishes to receive in a notification message in response to a change to the first data; second information identifying second data which the subscriber node wishes to receive with such a notification message; third information, different to the first information, specifying a condition to be fulfilled in relation to third data before such a notification message is sent; and fourth information specifying whether the subscriber node wishes to receive with such a notification message a version of the first data prior to the change; the first, second and third data each relating to the user and being held at the database node; and sending the subscribe message towards the database node; and at the database node: receiving the subscribe message sent from the subscriber node, the subscribe message comprising the first, second, third and fourth information; detecting a change to the first data identified by the received first information; in response to the detecting of such a change, and if it is determined that the condition specified in the received third information has been fulfilled, sending one or more notification messages towards the subscriber node, the notifcation message or messages comprising: the first data following the detected change; the second data specified by the received second information; and a version of the first data prior to the detected change. receiving the subscribe message sent from the subscriber node, the subscribe message comprising the first, second, third and fourth information; detecting a change to the first data identified by the received first information; in response to the detecting of such a change, and if it is determined that the condition specified in the received third information has been fulfilled, sending one or more notification messages towards the subscriber node, the notifcation message or messages comprising: the first data following the detected change; the second data specified by the received second information; and a version of the first data prior to the detected change.