An early model was the so-called “waterfall model” [Royce 70]. It is impressively simple and, in the past, enjoyed a high degree of popularity. Each development phase can only begin once the previous phase has been completed, hence the model’s name1. However, the model can produce feedback loops between neighboring phases that require changes to be made in a previous phase. Figure 3-1 shows the phases incorporated in Royce’s original model:
Fig. 3-1The waterfall model according to Royce
The major shortcoming of this model is that it bundles testing as a single activity at the end of the project. Testing only takes place once all other development activities have been completed, and is thus seen as a kind of “final check” akin to inspecting goods that leave a factory. In this case, testing is not seen as an activity that takes place throughout the development process.
Leave a Reply