What is Spiral Model

Spiral Model in Software Development Life Cycle (SDLC)

  • The spiral model is a risk-driven process model.
  • This is also called an incremental risk-oriented life cycle model
  • This is called a meta-model because it uses all other life cycle models (Waterfall and Prototype models).
  • The spiral model is suitable for the development of technically challenging software products that are prone to several kinds of risks.
  • As this is used for complex and critical projects then defiantly to implement any requirement Risk analysis requires specific expertise.
  • Example- Evolution of Microsoft Windows operating system.

Phases In Spiral Model

1. In the first phase, the requirements will be gathered.

2. Risks and alternative solutions will be identified.

3. The third step will be software and software tests are produced in the Development and Test phase.

4. Finally in the fourth phase, the output of the project so far is evaluated and the next iteration is planned.

1. Planning Phase/Determine Objectives:

  • Requirements are gathered during the planning phase. Requirements like ‘BRS’ that is ‘Business Requirement Specifications’ and ‘SRS’ is ‘System Requirement specifications.

2. Risk Analysis: 

  • In the risk analysis phase, a process is undertaken to identify risks and alternate solutions. A prototype is produced at the end of the risk analysis phase. If any risk is found during the risk analysis then alternate solutions need to be suggested.
  • Identify Risk: lack of experience, new technology.

3. Engineering Phase/Development and Test : 

In this phase, the software is developed, along with testing.

Typical activities:

  • Design
  • Implementation
  • Testing
  • Maintenance

4. Evaluation phase/Plan for next iteration: 

In this phase, the customer reviews the developed requirement and continues to the next spiral.

Typical  activities:

  • Develop project plan
  • Develop a test plan

When to use the Spiral SDLC Model?

When the project is large, complex, and critical.  
When risk and costs evaluation is important.

Advantages and Disadvantages of Spiral Model

Advantages of Spiral Model

  • Because of the Risk analysis phase, there are fewer chances of the project failing
  • Functionality can be added in the next phase because of the iterative nature of the process. 
  • Good for critical/complex projects.
  • Strong approval and documentation control.

Disadvantages of Spiral Model

  • Risk analysis requires highly specific expertise.
  • Risk analysis has to be done right.
  • Costly to implement.
  • Time management may be difficult. Usually, the end date of a project is not known at the first stages.
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