The spiral model

It could be argued that this is another way of looking at the basic waterfall model. In the waterfall model, there is a possible escape at the end of any of the activities in the sequence. A feasibility study might decide that the implementation of a proposed system would be beneficial. The management therefore authorize work on the detailed collection and analysis of user requirements. Some analysis, for instance the interviewing of users, might already have taken place at the feasibility stage, but a more thorough investigation is now launched. This might reveal that in fact the costs of implementing the system would be higher than originally estimated and lead managers to decide to abandon the project.

A greater level of detail is considered at each stage of the project and a greater degree of confidence about the probability of success for the project should be justified. This can be portrayed as a loop or a spiral where the system to be implemented is considered in more and more detail in each sweep and an evaluation process is undertaken before the next iteration is embarked upon. Figure 4.4 illustrates how SSADM can be interpreted in such a way.

The original ideas behind the spiral model can be found in B. W. Boehm's 1988 paper A spiral model of software development and enhancement'in IEEE Computer 21(5).

Project Management Made Easy

Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

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