Information Technology Reference
In-Depth Information
as the United Nations or the Bilateral Approach could be used to accomplish this
task
[56]
.
Autonomy—methods to allow different information sources to join and depart
the global information sharing environment at will. Autonomy comes in the
form of design autonomy, communication autonomy, execution autonomy, and
association autonomy.
Query processing and query optimization—methods to efficiently partition a
global query into sub-queries to allow parallel execution.
Transaction processing and concurrency control—methods to allow simultane-
ous execution of independent transactions and interleaving interrelated transac-
tions in the face of both global and local conflicts.
Data integration—methods to fuse partial results in order to draw global result.
This is particularly important because of the limited resources and capabilities
of mobile devices. With a very large amount of information available, the entire
set of data cannot be kept locally.
Browsing—methods to allow the user to search and look at the available in-
formation in an efficient manner without any information processing. This is
needed due to an enormous amount of information available to the user.
Distribution and location transparency—methods that allow efficient heteroge-
neous remote access to data sources while hiding the network topology and the
placement of the data. This is particularly important for wireless devices, which
have considerable communication cost. In addition, a high degree of mobility
argues for a high degree of heterogeneity—a mobile user can potentially access
a much wider variety of systems and data sources.
Limited resources—methods to accommodate computing devices with limited
capabilities. This includes memory, storage, display, and power.
Further discussion about these issues and their solutions is beyond the scope of
this chapter, however, research has extensively studied the aforementioned issues and
their solutions either within the scope of heterogeneous distributed systems
[10,11]
or mobile applications
[22,25,26,39,42,44,46,47,57,58]
.
1 . 2
B r o a d c a s t - B a s e d S e r v i c e s
Many applications are directed towards public information that are characterized
by (i) the massive number of users, (ii) the similarity and simplicity in the requests
solicited by the users, and (iii) the fact that data is modified by a few. The re-
duced bandwidth attributed to the wireless environment places limitations on the
