It is very simple to understand and use. In a waterfall model, each phase must be completed in its entirety before the next phase begins. At the end of each phase, a review takes place to determine whether the project is on track and whether or not to continue or abandon the project. In this model, testing only begins after development is complete. In the waterfall model, the phases do not overlap. Schematic of the CASCADE MODEL Figure1. 1 Advantages of the CASCADE MODEL • This model is simple and easy to understand and use. • A disciplined approach. • The waterfall model works well for small projects where the requirements are very well understood. • Progress in software development is visible. • In this model, the phases are processed and completed one by one. The phases do not overlap. Disadvantages of the CASCADE MODEL. • Bad model for long, ongoing projects. • Takes time. • Not a good model for complex, object-oriented projects. • Once an application is in the testing phase, it is very difficult to go back and change something that was not well thought out during the design phase. • High levels of risk and uncertainty. When to use the CASCADE MODEL • This model is used only when the requirements are very well known and clear.