Software Development Life Cycle

Software Development Life Cycle

1. SOFTWARE DEVELOPMENT LIFE CYCLE MODEL

   • The term software development life cycle model is a way of describing the planning, designing, coding, and testing of a software system, as well as the method in which these steps are implemented. A variety of life cycle models exist, but they all include the same constituent parts. All life cycle models take a project through several primary phases: a requirements-gathering phase, a design phase, a construction or implementation phase, and a testing phase. Figure 4-1 provides a simplified illustration of the general software development life cycle model.
     • Requirements
       • Design
         • Implementation
           • Testing

2. WATERFALL LIFE CYCLE MODEL

   • The waterfall model of SDLC uses traditional planning, testing, and implementation techniques to design and implement new software products. It represents a sequential development process in which progress is seen as flowing steadily downward through each phase of development.

3. V-SHAPED LIFE CYCLE MODEL

   • Like the Waterfall model, the V-Shaped life cycle model provides a sequential path of discrete phases that must each be completed before development proceeds to the next phase. The phase test plans are developed during each level of development, and once coding is completed, the tests are conducted. Figure 4-3 is a simplified illustration of the V-Shaped life cycle model.

4. INCREMENTAL LIFE CYCLE MODEL

   • In the incremental model, software is developed in parts—in different increments—and then are integrated as the parts are completed. The development team can return to different parts of the system during development to revise and improve the software. User input is sought for each cycle.

5. SPIRAL LIFE CYCLE MODEL

   • The spiral development model combines features of one or more SDLC models to best fit the development project at hand. For example, the following figure shows a spiral model that combines elements of a prototyping model with those of the waterfall model. The spiral model repeats earlier phases as the project progresses. Each cycle produces an early prototype representing a part of the entire project. This approach helps demonstrate a proof of concept early in the cycle and more accurately reflects the disorderly, even chaotic, evolution of technology.

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