Presence and instant messaging are changing the personal and corporate communications paradigm. Presence will enhance messaging as well as introduce a new service (the presence service itself) that can be used in many other applications and services. Presence will be the heart of all communications and the new way for telephony to function. Presence will also be a lucrative business opportunity for both operators and service providers.

Presence is a dynamic profile of the user, which is visible to others and used to represent oneself, share information and control services. Presence can be seen as a user's status as perceived by others and others' status as perceived by the user. Status may contain information such as personal and device status, location or context, terminal capabilities, preferred contact method as well as services the user is willing to use to communicate with others, including voice, video, instant messaging as well as gaming. Example is depicted in Figure 4.1.

Presence information is also personal: it is always linked to a particular person. It shows the person initiating the communication whether the other person is available and willing to communicate. On the other hand, presence information can be used to communicate to others when a person is able and willing to communicate as well as with whom and by what means. This will allow users to control their own communication more effectively.

Presence information sharing raises security and privacy ...

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