Describe three ways of sensing the presence of a user beside a display and thus motivate some
features required in an architecture for context-aware systems.

What will be an ideal response?

E.g. active badge sensor, face recognition by camera, voice detection.
An architecture for context-aware computing should (a) be able to accommodate such heterogeneous sensors;
(b) abstract values such as “user present” or “user X is present” from the data they provide; (c) deal with the
uncertainties and errors in the technologies, e.g. by fusing the results from several types of sensor; (d) detect
changes e.g. from absence to presence.