Spiral model key moments
November 21, 2019

Software Development

Your First Guide to the Spiral Model

By Olga Matuts

Similar to other types of software development life cycles, the spiral model has its unique characteristics, benefits, and disadvantages. 

The spiral approach is based on regular risk tracking on every stage of the project. This way,  it becomes clear what obstacles can hinder the team’s success.

Risk analysis requires special knowledge and qualification of the development team members. Thus the spiral model is more suitable for large projects that can cover the costs of top-notch professionals.

Spiral model structure

The spiral model implies a constant repetition of the basic development stages and risk elimination on each of them. For this iterative nature, the model was called spiral.

There are 4 key stages of the software development life cycle:

  • Gathering requirements
  • Risk analysis
  • Development
  • Evaluation

Let’s take a closer look at each of them.

Initial stage

In the beginning, team members collect project goals and requirements. In subsequent phases, they can act on customers’ feedback. Continuous communication between the customer and the development team is highly important at this stage.

Risk analysis stage

The development team has to find, assess, and eliminate project risks. Risks are understood as possible conditions, which can prevent the development team from reaching the customer’s goals. It is necessary to foresee and prioritize all expected risks. After that, the development team has to find potential strategies to eliminate the risks that can affect success at the next level. At the end of this stage, a prototype is created. The initial version of the product that is delivered before getting customer feedback is called the Proof of Concept, or POC.

Development stage

This stage includes the very coding of the software product, followed by verification and testing. At this and the next stages, the product is called the Build. Developers deliver the version to the customer for more detailed feedback and precise requirements.

Evaluation stage 

Developers and project managers evaluate the current results of the project and plan a new stage before the next spiral starts.

The Spiral model comprises the elements of the Waterfall and Prototype models and thus is sometimes called a metamodel.  The lifecycle of the real project is more flexible than a theoretical scheme, and there is a possibility to change a previous decision.

Strengths and weaknesses of the Spiral Model

The spiral model has its benefits and disadvantages, just like other methods of software development.

Let’s review some of them:

Strengths:

  • Risk tracking as the basis of the Spiral model is crucial for managing an expensive and large project. It makes the project clearer for the team because it requires reviewing and analyzing results on every step.
  • Customers can get acquainted with the working version of the project at the initial stage of development.
  • Customers can make changes to the project at the late stages of software development.
  • It is possible to divide the project into parts and develop the risky ones first. This approach simplifies the management of the project.
  • Information about the costs and timing of the project becomes more real as the spiral ends.
  • Documentation is clear and accurate.

Weaknesses:

  • The spiral model can be expensive because risk analysis requires special knowledge and experience.
  • This approach implies a lot of intermediate stages and, as a result, a lot of documentation.
  • At the initial stage, it is hard to specify the exact date of the project rollout, which makes time management more difficult.

The spiral model is a good decision for high-risk software development projects when it is very important to foresee the costs, there are no definite requirements, and significant changes are possible during development.

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