Waterfall Approach/Model

This method is known as the Waterfall process or Waterfall approach because developers build monolithic systems in one fell swoop. It requires completing the artefacts of the current phase before proceeding to the subsequent one.

The drawback of this approach is the difficulty of accommodating change after the process is underway. Just like a physical waterfall where water cannot flow upwards, the Waterfall approach does not permit going back to previous phases. This approach is therefore only appropriate when requirements are well defined and changes only limited during the design phase. In reality, few business systems have stable requirements. The Waterfall model is mostly used for large systems engineering projects where a system is developed at several sites. In those circumstances, the plan-driven nature of the waterfall model helps coordinate the work.