2. Waterfall method

With the waterfall method the project is split up into a number of stages, with each stage having a specific purpose. The end of each stage is called a milestone.

The method is sequential so it looks like a cascade or waterfall.

In the 'pure' waterfall method, there is no iteration - once a stage is passed it is not re-visited, i.e. you cannot go back.

However, in reality, most projects involve a variation of the pure waterfall method as they do go back to an earlier stage if something changes. This is known as the 'modified waterfall method'.

The waterfall method is shown below

From the diagram it is clear that a late change to a project can have a massive impact on delivery date and costs.

For example, if the project had progressed to the 'install' stage and suddenly a change was requested then according to the pure waterfall model you would not be able to go back through the stages to make that change. Instead you would have to go back right to the beginning and start over at the 'Define Requirements' stage.

Stages of the waterfall method

Define Requirements: Describe the overall purpose of the project and define what each stakeholder wants out of it. (a stakeholder is anyone who is impacted in some way by the new software).

Analysis: Assess the costs, time, manpower and resources needed for the project.

Design: Work out how the software is to be structured and created.

Implement: Carry out the coding.

Test: Plan how the software will be tested, then carry out tests to confirm that the software works as intended.

Install: Roll out the software to the users, this can be done all at once or the new software can be phased in over time in order to reduce disruption.

Maintain: Fix any bugs that were not picked up during testing and keep the software up to date.