3. Software engineering life cycle

Software is a complex whole, and its development requires a diversity of activities. An effective technique for controlling the complexity of a whole is to subdivide it into several parts, to make it controllable. It is therefore essential to structure the approach to software quality. What's more, representing the real world involves abstraction, which leads to the use of a model. Thus, modeling or reducing the real world, introduces the notion of successive activities, hence the concept of "life cycle". Modeling is convenient and doubly useful. It provides a logical, graphical representation and, what's more, it offers a structure around which quality assurance activities can be built and monitored.

The life of a software or information system is broken down into characteristic phases representing homogeneous sets of activities that need to be placed under quality...