Overview

A system is an entity that provides some behavior to its environment, where the environment can consist of people or other systems. In the previous chapter we saw that expected behavior of a proposed software system is defined through a software requirement specification (SRS) document. For building the specified software system, designing the software architecture is a key step, and is the topic of this chapter.

Any complex system is composed of sub systems that interact under the control of system design such that the system provides the expected behavior. While designing such a system, therefore, the logical approach is to identify the sub-systems that should compose the system, the interfaces of these subsystems, and the rules for interaction between the subsystems. This is what software architecture aims to do.

Software architecture is a relatively recent area. As the software systems increasingly become distributed and more complex, architecture becomes an important step in building the system. Due to a wide range of options now available for how a system may be configured and connected, carefully designing the architecture becomes very important. It is during the architecture design where choices like using some type of middleware, or some type of back end database, or some type of server, or some type of security component are made. It is not possible to design the details of the system and then try to accommodate these choices the architecture must be created such that these decisions have been incorporated suitably in the system structure.