The IMS: IP Multimedia Concepts And Services, Second Edition

4.4. What is presence?

Presence is in essence two things: it involves making my status available to others and the statuses of others available to me. Presence information may include:

• person and terminal availability;

• communication preferences;

• terminal capabilities;

• current activity;

• location;

• currently available services.

It is envisioned that presence will facilitate all mobile communication, not only instant messaging, which has been the main driver for presence. Instant messaging has been the main interactive, almost real-time communication service in the Internet and presence is a great compliment in that you know if a friend is online before you begin a chat session with her. However, in the mobile environment, it is envisioned that presence information will not only support instant messaging, it will also be used as an indicator of the ability to engage in any session, including voice calls, video and gaming: all mobile communications will be presence-based.

Presence-specific and presence-enhanced applications and services will be available in the near future. A typical example of a presence-specific application will be a phone-book with embedded presence information, making it dynamic. Dynamic presence (Figure 4.1) will be the initial information the user sees before establishing communication. This information affects the choice of communication method and timing.