Spiral Model

1.    This model possesses the iterative nature of prototyping model and controlled and systematic approaches of the linear sequential model.

2.    In this model, the software is developed in a series of increments.

3.    The spiral model is divided into a number of framework activities. These framework activities are denoted by task regions.

4.    Usually there are six tasks regions.

5.    Spiral model is realistic approach to development of large-scale systems and software. Because customer are developer better understand the problem statement at each evolutionary level. Also risks can be identified or rectified at each such level.

6.    In the initial pass, product specification is built and in subsequent passes around the spiral the prototype gets developed.

7.    During planning phase, the cost and schedule of software can be planned and adjusted based in feedback obtained from customer evaluation.

8.    In spiral model, project entry point axis is defined. This axis represents starting point for different types of projects.

9.    The task region can be described as-

i.      Customer communication – In this region it is suggested to establish customer communication.

ii.    Planning – All planning activities are carried out in order to define resources time line and other project related activities.

iii.   Risk analysis – The tasks required to calculate technical and management risks are carried out.

iv.    Engineering – In this task region, tasks required to build one or more representations of applications are carried out.

v.     Construct and release – All the necessary tasks required to construct, test, install the application are conducted.

vi.    Customer evaluation – Customer’s feedback is obtained and based on customer evaluation required tasks are performed and implemented at installation stage.

10.  In spiral model, the software engineering team moves around the spiral in a clockwise direction beginning at the core.

Advantages of spiral model

1.    Requirement changes can be made at every stage.

2.    Risks can be identified and rectified before they get problematic.

Disadvantages of spiral model

1.    It is based on customer communication. If the communication is not proper then the software product that gets developed will not be up to mark.

2.   It demands considerable risk assessment. If the risk assessment is done properly then only the successful product can be obtained.