Difference between Spiral Model and Waterfall Model



Both the Spiral Model and the Waterfall Model are widely used development methodologies in the software industry. Both of these models are practices for better tracking and have application development in systematic way. The basic difference between spiral model and waterfall model is that the spiral model works in evolutionary method and generally used by developers, whereas the waterfall model works in a sequential method and generally used by customers.

In this article, we will discuss the important differences between spiral model and waterfall model. But before going into the differences, let's start with some basics of these two models.

What is the Spiral Model?

Spiral Model is the development model in which the entire model is divided into various subdevelopment phases where corresponding testing phase for each development phase is practices. The spiral model is generally used by the developers of the application. In the spiral model, the early stage planning is not required. It is mainly used with large projects.

The spiral model works in evolutionary method. It identifies and removes the errors and risks before the completion of stages. The main advantages of the spiral model are – flexibility, less risk, can be easily changed as required. But, it is a very expensive model.

What is the Waterfall Model?

The waterfall model works in the sequential method and is generally used by customers. It requires early-stage planning. Waterfall model is the first development of an application, after which the application is tested.

In the Waterfall model, the errors and risks are determined and removed after the stages are completed. It is suitably used with small projects because it is less flexible, difficult to change, and involves high amount of risk. But, it is relatively less expensive than spiral model.

Difference between Spiral Model and Waterfall Model

The following table compares and contrasts the different features of the Spiral model and the Waterfall model −

Factor Spiral Model WaterFall Model
Definition Spiral Model is the development model in which the entire model is divided into various sub development phase where corresponding testing phase for each development phase is practices.
In other words, we can say that for every stage in the development cycle, there is an associated testing phase and corresponding testing phase of the development phase is planned in parallel.
Waterfall model there is first development of the application and after which the different testing of application take place.
In other words, we can say that the complete process is divided into several phases among which one phase should be completed in order to reach the next phase and testing is almost at end phase of the development.
Type/Nature As mentioned above that in Spiral Model the execution of the phases i.e., development and testing happens in a sequential manner, so the type of Spiral Model is evolutionary in nature. Waterfall Model is a relatively linear sequential design approach as each phase should be completed in order to reach the next phase. So the type of this model is Continuous in nature.
Testing and Validation In the Spiral Model each development phase get tested at its own level and hence no pending testing occurs in this model also if any validation requires to be implemented then it could be implemented at that phase. In case of Waterfall Model, the testing occurs after development is completed and thus if any missing validation is identified to be implemented then first that phase of development needs to be recognized and then that validation get implemented.
Cost and Complexity As sequential phases need to be functional hence the cost is higher as compared to that of WaterFall Model also the complexity is more than WaterFall. In the Waterfall Model, due to linear development only one phase of development is operational and hence cost and complexity is low as compared to that of Spiral Model.
Defects In the Spiral Model the probability of total number of defects in the development of application is low as testing is done in parallel to the development. In the Waterfall Model, the probability of total number of defects in the development of application is high as testing is done post development.

Conclusion

The most significant difference that you should note here is that the spiral model is generally used by developers, whereas the waterfall model is used by customers.


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