ISTQB - Spiral Model

In last article we have understood about the iterative model and in this article we will get details about the spiral model. This model is one kind of software development life cycle model. 

This model is well known for risk handling. As here model is divided in many loops of software development. Loop of the model will not be identified or it does not have fix count as per the project and development requirements, loop will be decided for develop a product or application so basically we can say that loop count is unknown here. Loop will be define as the phase of software development life cycle. The count of the phases required to develop a product will be known as the loop of the model. The phase of the software development life cycle will be confirmed by the project manager with respect to product risk. Thus, the loop of the software development can be varied as per the planning. Here whole project development will be handled by the project manager and he is the main lead who will decide the software development phases or loops so in spiral model, Project Manager is the most important person or we can say that he is playing main role of the model.

This model is used for large project and it includes continuous enhancements. Many types of phases have been defined here, like planning & design phase, risk analysis phase, evolution phase, Review & next plan phase.

Planning & Designing Phase:  

In this phase all the requirements are gathered and simple model of the application will be prepared and all the areas of the application will be analyzed deeply at the starting of the each level of spiral model. Thus, solution for every problem can be identified in this level and then further steps will be taken for developing whole product or application. First level will be started from the base line of spiral and further that spiral will be divided in different levels and accordingly development will be evaluated. Afterwards design of the product will be identified like physical design, logical design and final design will be completed with the subsequent spiral levels.

Risk Analysis:

Risk and alternative solutions for the product will be define in this phase. If any risk will be found in after designing or after developing some piece of code then how to resolve the same that can be identified in this level and alternative solution will be found for a product. A risk will be resolve with the different strategy and it will be done with best solution.

Evolution:

In this phase, Development will be done and afterwards testing of the application will take place. Here we need to ensure that a developed product is bug free and all the requirements of the client have been full filled. Not a single critical bug will be found after the testing will be completed. In this level we will complete a release of the current version and move to the next one.

Review & Next Plan:

In this phase, whole developed product will be shared with client and their reviews will be define, any changes or updates required here then that will be discussed and implemented. Afterwards planning of the next phase will be done here with respect to older releases. Risk will be analyze here deeply and as per the requirements next build level will be begun by team. 

When to use Spiral Model:

1. When risk factor is high in project then this model is perfect to use as more risk evolution is taken place here.
2. When significant changes and analysis will be required in project then this model is the perfect choice of software development model.
3. Requirements are not easy and client is not sure for their needs at that time this model can be used.
4. If project commitment was done for long time then it would be fine to select this model as product development model.

Advantages of Spiral Model:

1. Risk can be handled and different strategy can be applied here to develop a good product.
2. Documentation needs to be perfect here & good for Log term Project.
3. Updates and changes can be implemented in middle of the development and software can be identified in the early stage of life cycle.

Disadvantages of Spiral Model:

1. If risk will not be identified then project can be leads to failure.
2. High cost is required here.
3. Experience person is required here to resolve the risk so we can’t assign a project to fresher resource.
4. Can’t implement this mode to small projects.