1. A data processing apparatus having one or more processors, the apparatus comprising: a plurality of application programs executable by the one or more processors, the plurality of application programs configured to utilize an availability status of a user; and a presence engine configured to: receive data representative of the availability status of the user; generate one or more representations of the received availability status suitable for one or more of the plurality of application programs; make available the one or more representations of the received availability status to the corresponding one or more of the plurality of application programs; determine which of the plurality of application programs have been recorded as utilizing the availability status of the user; and provide those application programs that have been recorded as utilizing the availability status of the user with the representation of the availability status that is suitable for that application program.