Context-Aware Applications - Guide to Cloud Computing for Business and Technology Managers - page 510

• There is a gap between how people understand context and what
systems consider as context. The environment in which people live
and work is very complex; the ability to recognize the context and
determine the appropriate action requires considerable intelligence.
• A context-aware system cannot decide with certainty which actions
the user may want to be executed; as the human context is inacces-
sible to sensors, we cannot model it with certainty.
• A context-aware system cannot be developed to be so robust that it
will rarely fail, as ambiguous and uncertain scenarios will always
occur and even for simple operations exceptions may exist.
• A context-aware system can add more and more rules to support the
decision-making process; unfortunately, this may lead to large and
complex systems that are difficult to understand and use.
• A context-aware application is based on context information that
may be imperfect. The ambiguity over the context soundness arises
due to the speed at which the context information changes and the
accuracy and reliability of the producers of the context, like sensors.
It is a challenge for context-aware systems to handle context, which may be
nonaccurate or ambiguous, in an appropriate manner—more information is
not necessarily more helpful; context information is useful only when it can
be usefully interpreted.
23.3 Context-Aware Mobile Applications
A mobile application is context aware if it uses context to provide relevant
information to users or to enable services for them; relevancy depends on a
user's current task (and activity) and profile (and preferences). Apart from
knowing who the users are and where they are, we need to identify what
they are doing, when they are doing it, and which object they focus on. The
system can define user activity by taking into account various sensed param-
eters like location, time, and the object that they use. In outdoor applications,
and depending on the mobile devices that are used, satellite-supported tech-
nologies, like GPS, or network-supported cell information, like GSM, IMTS,
and WLAN, is applied. Indoor applications use RFID, IrDA, and Bluetooth
technologies in order to estimate the users' position in space. While time
is another significant parameter of context that can play an important role
in order to extract information on user activity, the objects that are used in
mobile applications are the most crucial context sources.
In mobile applications, the user can use mobile devices, like mobile phones
and PDAs and objects that are enhanced with computing and communication