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BENEFITS
Specific benefits of the multi-tier architecture approach are as fol-lows :
HCommon goals
HCommon semantic model
HParallel development
HBehavioral discretion
HSpecialization of skills
HDebugging
Common Goals
The first benefit is not derived specifically from a multi-tier archi-tecture but from the management approach a project takes to realize it. Specifically, by describing the functionality of the system in terms of use cases(an object-oriented requirements and analysis technique pioneered by Ivar Jacob-son [2]), every developer works from the same conceptual under-standing of the goals of the system.
Of course, this does not mean each developer works in the same manner or even does the same task. Your Web page designer is likely to approach her job quite..
BACKGROUND AND ASSUMPTIONS
The basic structure of a multi-tier application architecture is presented in Figure 1. Each tier is responsible for a specific set of services. The architecture shown in Figure 1 is admittedly biased toward the development of object-oriented systems, the application technology with which.
I am most familiar, but it can be easily extended to other technologies. Such an architecture follows the basic principle for encapsulation that Edsger Dijkstra [1] outlined in the late ’60s: tiers at lower levels of abstraction “know” as little as possible about layers at higher levels of abstrac-tion. The heart and soul of a good application are the domain objects that comprise the business rules and data. It is foolish to try to slap a high-quality user interface onto a contrived set of objects. Similarly, there is little to be gained from letting your ex- isting legacy database systems drive the internal structure of your domain objects. A thor- ough and complete analysis of the problem domain, expressed in the notation of your favorite object-oriented methodology, is your best chance for success in the crafting of such an architecture. This leads to the final point of this brief review: effective man- agement practices are absolutely essential if you plan to create an effective multi-tier application architecture. Fortunately, as I’ll explain shortly, explicitly striving to build such an architecture right from the beginning makes following such practices far easier.
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