The six-phase model is a waterfall model. In other words, the phases take place in succession. Just as it is impossible to swim upstream against a waterfall, the pure waterfall method does not allow returning to a phase after it has been completed.
During the implementation phase, it is not desirable to decide to adapt the design, thereby bringing implementation to a standstill. For a number of reasons (see e.g. McConnell, 1996; Kroll, 2004; Chromatic, 2003; Stapleton, 2002), the waterfall method is usually less suited to software-development projects:
- Software development is a creative process.
- It is nearly impossible to identify all of the requirements (functionalities) beforehand.
- Estimating the amount of time that will be necessary to implement a functionality is quite difficult.
- It should be possible for all intermediate results to be tested by users throughout the entire trajectory of the project.
Note: The above points will be discussed in details in separate articles.
Wouter Baars has a Master of Science degree in Industrial Engineering and Management Science. He has been a project manager for several years for The European commission, Waag Society, KPN (Dutch telecom provider) and many smaller organizations. He is specialized in creative projects such as serious game development, e-learning and software development. Currently he is teaching project management and coaching organizations that are working on their project management. More info on his work: www.projectmanagement-training.net.
Originally published by DANS – Data Archiving and Networked Services – The Hague