Waterfall (a.k.a. Traditional) Methodology
The waterfall model is a popular version of the systems development life cycle model for software engineering. Often considered the classic approach to the systems development life cycle, the waterfall model describes a development method that is rigid and linear. Waterfall development has distinct goals for each phase of development where each phase is completed for the next one is started and there is no turning back.
The perceived advantages of the waterfall process are that it allows for departmentalization and managerial control. A schedule is typically set with deadlines for each stage of development and a product can proceed through the development process. In theory, this process leads to the project being delivered on time because each phase has been planned in detail.
In practice, waterfall development often falls short of expectations as it does not embrace the inevitable changes and revisions that become necessary with most projects. Once an application is in the testing stage, it is very difficult to go back and change something that was not thought of in the concept stage. Alternatives to the waterfall model include joint application development (JAD), rapid application development (RAD), sync and stabilize, build and fix, and the spiral model