Page 46 - DCAP405_SOFTWARE_ENGINEERING

Unit 3: Process Models

programming is completed, the code is integrated and testing is done. On successful completion Notes
of testing, the system is installed. After this, the regular operation and maintenance of the
system takes place. The model is shown in Figure 3.2.
We will discuss the activities related to the development of software. Thus, we will only discuss
phases from requirements analysis to testing. The requirements analysis phase is mentioned as
“analysis and planning.” Planning is a critical activity in software development. A good plan is
based on the requirements of the system and should be done before later phases begin. However,
in practice, detailed requirements are not necessary for planning. Consequently, planning usually
overlaps with the requirements analysis, and a plan is ready before the later phases begin. This
plan is an additional input to all the later phases.

Task Explain how waterfall model comes under the perspective modeling? Give examples
to support your answer.

With the waterfall model, the sequence of activities performed in a software development
project is: requirement analysis, project planning, system design, detailed design, coding and
unit testing, system integration and testing. This is the order in which the different phases will
be discussed in this book, keeping the sequence as close as possible to the sequence in which the
activities are performed.
Linear ordering of activities has some important consequences. First, to clearly identify the end
of a phase and the beginning of the next, some certification mechanism has to be employed at
the end of each phase. This is usually done by some verification and validation means that will
ensure that the output of a phase is consistent with its input (which is the output of the previous
phase), and that the output of the phase is consistent with the overall requirements of the
system.

Figure 3.2: Waterfall Model

Requirements
analysis and

specification
Software
design

Construction

Testing

Operation and
maintenance

The consequence of the need for certification is that each phase must have some defined output
that can be evaluated and certified. That is, when the activities of a phase are completed, there
should be some product that is produced by that phase. And the goal of a phase is to produce this
product. The outputs of the earlier phases are often called work products (or intermediate
products) and are usually in the form of documents like the requirements document or design
document. For the coding phase, the output is the code. From this point of view, the output of a

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