Distributed Systems - Guide to Cloud Computing for Business and Technology Managers - page 70

business service providers, and service consumers, the n-tier archi-
tecture creates software infrastructure of reusable parts.
• Maintainable software : The n-tier architecture is useful in creating
more maintainable and easily upgradeable software. Because soft-
ware components are stand-alone reusable parts of business logic,
they are used from the same place without the need for multiplica-
tion or replication and are therefore easier to change and upgrade,
rendering the application as a whole more easily maintainable.
• Reliable software : The n-tier architecture is useful in creating more
testable, more easily debuggable, and thus more reliable software.
Flexible and maintainable software does not automatically imply
reliable software, but because software components are stand-alone
packets of business logic, bugs can be localized more easily and their
functionality can be calibrated more accurately, rendering the appli-
cation as a whole more reliable.
• Reduced complexity : The n-tier architecture is useful in creating more
streamlined, simplified, and standardized software because the
software component paradigm eliminates the need for custom inter-
connections between disparate constituents of a composite applica-
tion (which includes existing and legacy systems) that increase in
complexity rapidly with the increase in the number of disparate
constituents. For instance, for a composite application constituted
of n applications and m data sources, the problem of correspond-
ing n × m interconnections is barely manageable even for small val-
ues of n and m. However, in the n-tier architecture, this problem
is resolved to a great extent by interfacing all components to (say)
a single standardized data bus—this reduces the problem of m × n
interconnections to that of only n + m interconnections! All compo-
nents can connect with each other via connections to this singular
data bus without the need for multiple customized single-purpose
interconnections between each pair of components.
The interfacing approach of point-to-point interfaces between
two applications would be prohibitively expensive for EAIs that
may involve tens and hundreds of such interfaces. EAIs also
adopt the alternate approach of instituting an information bro-
ker whereby all systems communicate with the information broker by
uploading data into the same while simultaneously translating them
into a single format and protocols native to this central broker. Because
information is routed through the information broker, rather than
going directly among different systems, this simplifies the problem
considerably and it becomes easy to connect disparate systems via their