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24 CHAPTER 2 Introduction to Enterprise Systems

ARCHITECTURE OF ENTERPRISE SYSTEMS
The architecture of an enterprise system refers to the technical structure of the
software, the ways that users interact with the software, and the ways the soft-
ware is physically managed on computer hardware. Most modern ES have either
a three-tier client-server architecture or a service-oriented architecture. There
are many different ways to deploy ES in these two architectures. Both models
offer distinctive technical and cost benefi ts, and both models have drawbacks.
Nevertheless, the impact of these two models on the management of business
processes is largely the same. We examine both types of architecture below.

Client-Server Architecture

Think of a desktop application that you routinely use, such as word process-
ing, spreadsheet, or presentation software. These applications consist of three
components, or layers: (1) how you interact with the application (using menus,
typing, and selecting); (2) what the application allows you to do (create for-
mulas or charts, compose an essay); and (3) where the application stores your
work (on your hard drive or fl ash drive). These layers are the presentation
layer, application layer, and data layer, respectively. In the desktop appli-
cations mentioned above, all three layers are contained in one system. In con-
trast, the three-tier client-server architecture separates these layers into
three separate systems, as illustrated in Figure 2-1.

Figure 2-1: Three layers of the client-server architecture

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