Context-Aware Applications - Guide to Cloud Computing for Business and Technology Managers - page 509

situation, for instance, from illumination, temperature, noise level, and device
movements. A context-aware application can make adaptive decisions based
on the context of interaction in order to modulate the information presented
to the user or to carry out semantic transformation on the data, like convert-
ing text to speech for an audio device. The promise and purpose of context
awareness are to allow computing systems to take action autonomously and
enable systems to sense the situation and act appropriately. For example, in
context-aware mobile applications, location is the most commonly used vari-
able in context recognition as it is relatively easy to detect. User activity is
much more difficult to identify than location, but some aspects of this activ-
ity can be detected by placing sensors in the environment.
Location is the most commonly used piece of context information, and
several different location detection techniques have been utilized in con-
text-awareness research. Global positioning system (GPS) is a commonly
used technology when outdoors, utilized, for example, in car navigation
systems. Network cellular ID can be used to determine location with mobile
phones. Measuring the relative signal strengths of Bluetooth and WLAN
hotspots and using the hotspots as beacons are the frequently used tech-
niques for outdoor and indoor positioning. Other methods used indoors
include ultrasonic or infrared-based location detection. Other commonly
used forms of context are time of day, day of week, identity of the user,
proximity to other devices and people, and actions of the user.
Context-aware device behavior may not rely purely on the physical envi-
ronment. While sensors have been used to directly provide this physical
context information, sensor data often need to be interpreted to aid in the
understanding of the user's goals. Information about a user's goals, prefer-
ences, and social context can be used for determining context-aware device
behavior as well. Knowledge about a user's goals helps prioritize the device
actions and select the most relevant information sources. A user's personal
preferences can offer useful information for profiling or personalizing ser-
vices or refining information retrieval. The user may also have preferences
about the quality of service issues such as cost efficiency, data connection
speed, and reliability, which relate closely to mobile connectivity issues deal-
ing with handovers and alternative data transfer mediums.
Finally, social context forms an important type of context as mobile devices
are commonly used to support communication between two people and
used in the presence of other people.
Challenges of context-aware systems include the following:
• A main issue regarding context-aware computing is the fear that con-
trol may be taken away from the user. Apart from control issues, pri-
vacy and security issues arise. The main parameters of context are user
location and activity, which users consider as part of their privacy.
Users are especially reluctant to exploit context-aware systems, when
they know that private information may be disclosed to others.