Page 49 - DCAP405_SOFTWARE_ENGINEERING

Software Engineering

Notes To state requirements explicitly,
To gather all the knowledge necessary for planning the entire project in the beginning.
The waterfall model’s original objectives were to make small, manageable, individual
development steps (the phases) and to provide enough control to prevent runaway projects.
There are a few problems that have caused dissatisfaction with this phased life-cycle
approach.
The new software system becomes useful only when it is totally finished, which may
create problems for cash flow and conflict with organizational (financial) objectives or
constraints. Too much money may be tied up during the time the software is developed.
Neither user nor management can see how good or bad the system is until it comes in. The
users may not have a chance to get used to the system gradually.
Changes that “aren’t supposed to happen”, are not viewed kindly, neither for requirements
nor during the operational life of the system. This can shorten the software’s useful life.

Because of these shortcomings, other process models have appeared. They are based on the
concept of iteration and evolution.
Waterfall model, although widely used, has some limitations. Here we list some of these:

Despite these limitations, the waterfall model is the most widely used process model. It is well
suited for routine types of projects where the requirements are well understood. That is, if the
developing organization is quite familiar with the problem domain and the requirements for
the software are quite clear, the waterfall model works well.

Self Assessment

Fill in the blanks:
1. The design starts after the requirements analysis is complete and ………………….. begins
after the design is complete.
2. ……………………….. is a critical activity in software development.
3. The consequence of the need for ……………………….. is that each phase must have some
defined output that can be evaluated and certified.
4. A successful software product is one that satisfies all the objectives of the
………………………. project.
5. Schedule compression relaxes this requirement but introduces new…………………………..
6. The waterfall model’s original objectives were to make small, …………………….,
individual development steps to provide enough control to prevent runaway projects.
7. Requirement Specification document (SRS) is produced which contains the detailed
description of what the system will do in the …………………… language.
3.2 Incremental Process Models

3.2.1 Incremental Model

The incremental model is an intuitive approach to the waterfall model. Multiple development
cycles take place here, making the life cycle a “multi-waterfall” cycle. Cycles are divided up into

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