Waterfall model

Summary

The Big Idea

Description of the model in phases

The waterfall project management model is broken down into a series of consecutive stages. The classic model has six phases:

• 1- Requirements

This phase corresponds to the expression of needs [6]. First of all, the customer's requirements for the product are documented: the functions and the expected performances. The customer and the project team work together to establish a Requirement Specification Document [2].

• 2- Analysis

In some models, the analysis phase is included in the requirement phase [2]. In this second step, the requirements are analysed and the schemas and models for the product are defined.

• 3- Design

From the specifications, the functions and requirements are transformed into a feasible product. The product is specified and its architecture is designed [11].

• 4- Implementation

This step is the passage in a concrete phase of realisation of the product. While the first three phases are more about planning and mock-up, during this one, a first version of the product is developed [1].

• 5- Testing and Validation

The completed product undergoes a series of tests to compare it with the specifications and verify that it meets the requirements. During this phase, we identify the defects of the product. The quality of the final product depends largely on the efficiency of the testing phase [2]. At the end of this phase, if it passes all the requirements, the product is validated.

• 6- Release

Once a final product is approved, its commissioning is prepared. Then the product is installed and used [6].

A final maintenance phase is added, often in software development companies [11]. This seventh phase corresponds to the work of the company to make sure that the product works as expected once implemented and to intervene in the opposite case to solve problems that may arise. Like a waterfall, the different phases of this model follow each other consecutively and chronologically. One cannot move on to a new step without having validated the previous one and each step must be accompanied by solid documentation. The first person to theorise this model was W.W. Royce in 1970. In his article: Imagining the development of large software system, he represents graphically the phases of the model without using the name waterfall. In his article, Royce already criticises this model at the time [1].