This model of development combines the features of the protyping and the waterfall model. The spiral model is intended for large, expensive and complicated projects. It was first proposed by Boehm. In the spiral model we can arrange all the activities in the form of a spiral.Each loop in a spiral represents a development phase (and we can have any number of loops according to the project). Each loop has four sections or quad.
Based on the feedback, software development process enters into the next iteration and subsequently follows the linear approach to implement the feedback suggested by the customer. The process of iteration continues throughout the life of the software.
In the first quadrant we get to know the project objectives and the limitations because of time, budget and the development of technology.
In the second quadrant we discover is there any other ways that can be used to avoid the constraints that have already been identified. Evaluation of all these factors determine will the project go ahead.
In the third quadrant we develop the planned product. Testing is done here and sees can it be brought to the final stage. In order to do development the waterfall approach can be used.
In the 4 th quadrant we review the progress and judge it considering all parameters. Issues which need to be resolved are identified in this phase and necessary steps are taken.
An example of the spiral model is the Microsoft Windows Operating system from Windows 3.1 to windows 2003. We see Microsoft windows 3.1 Operating System as the first iteration in the spiral approach. The product was released and evaluated by the customers, which include the market large. After getting the feedback from customers about the windows 3.1, Microsoft planned to develop a new version of windows operating system. Windows’95 was released with the enhancement and graphical flexibility. Similarly, other versions of windows operating system were released.
Next week i will talk about the advantages and disadvantages of the spiral model
Introduction to Systems Analysis and Design by Igor Hawryszkiewycz