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Monday, January 24, 2022

What Is Spiral Model? | Type of SDLC Models

What Is Spiral Model? | Type of SDLC Models

Spiral Model


  • The spiral model is a risk-driven process model.
  • This is also called as incremental risk oriented life cycle model
  • This is called meta-model because it uses all other life cycle models (Waterfall and Prototype models).
  • The spiral model is suitable for 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 through specific expertise.
  • Example- Evolution of Microsoft Windows operating system.

Spiral Model
Spiral Model

Phases In Spiral Model

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

2. Risks and alternative solutions will be identified.

3. Third step will be software and software test 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’ that is ‘System Requirement specifications’.

2. Risk Analysis: 

  • In the risk analysis phase, a process is undertaken to identify risk 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 software is developed, along with testing.

Typical activities:

  • Design
  • Implementation
  • Testing
  • Maintenance

4. Evaluation phase/Plan for next iteration: 

In this phase customer review 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 Risk analysis phase, there is less chances of project to fail
  • Functionality can be added in the next phase because of 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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