In 1986, the spiral model was proposed by Barry Boehm.
Spiral model is based on the evolutionary model which is the combination of linear sequential model and iterative software development model.
This model is suitable for large and complex projects.
Spiral model is based on spirals (iterations) to develop a project.
A phase in the software development life cycle is a loop of the spiral.
This model works very well for large projects because it involves constant improvements until a final product is not build.
The whole development process is completed in the 4 phases.
The phases are :
Planning
Risk analysis
Development and testing
Evaluation
Phases of spiral model :
Planning :
The requirements are collected from the clients.Feasibility study is done in this phase. It includes cost estimation, schedule, objectives are defined and other resources for the iteration to develop a software project.
Risk analysis :
In the second phase of development, risks are identified and find different solutions to remove risks. If any risk is find out during the phase then alternate solutions are designed and implemented the best way among them.
Development and testing :
After risk analysis phase is completed, the software product is developed and tested at the end of each iteration so there is development and testing applied at same phase.
Evaluation :
In the last phase, the feedback is taken from the customer and evaluate the developed project after completion of each iteration. To carry on next iteration, evaluation phase is completed.
Advantages of Spiral Model :
This model is good for large and complex projects.
Updates are received to the customer at each iteration.
Spiral model is suitable to change the requirements at any time, any phase.
Risks are analyzed after each iteration.
Documentation is clearly defined and understandable.
Disadvantages of Spiral Model :
Spiral model is not good for small projects.
This model is more complex and difficult to understand if a new employee is entered in the project development.
It can be much expensive.
Fast development and software is built at the SDLC .
Not defined end points of the project , so it can take a long time to develop or iterations can be go infinitely.
