In this post, we’re continuing our series of highlighting various development methodologies by taking a closer look at the Spiral development approach – outlining its key features as well as its advantages and disadvantages.

How does the Spiral method work?

The Spiral software development methodology was designed to combine features of various incremental prototyping methods with the Waterfall model. It is considered to be best suited for large scale projects which might need more planning and risk management.

The Spiral model is built around a four-phase development cycle. The development progresses in an iterative way, as it effectively loops through the various stages of the development cycle – like a spiral. There can be any number of loops, depending on the size of the project.

What are the four main phases of each Spiral cycle?

  1.  The Planning Phase
    In this first phase requirements are established, in the shape of Business Requirement Specifications ‘BRS’ and System Requirement Specifications ‘SRS’. The developers will try to understand the objectives of the product and consider design options – whilst looking at any constraints such as costs, technology, and timescales.
  2. The Risk Analysis
    This phase focuses on identifying and evaluating risk, and considering alternative solutions. The development team will try to find implementation approaches that deal with any constraints, as well as operational and technical issues.
  3. The Engineering Phase
    This is the phase where software is developed and tested, using Waterfall or incremental development processes. Because of the successive cycles and appraisals of the end product, the software can be said to ‘evolve’ throughout the overall project.
  4. The Evaluation Phase
    In the evaluation phase, the current project output is reviewed and evaluated before the project moves on to the next spiral. Any critical issues will be identified here, and the necessary steps will be taken to deal with them.

At the end of each cycle of phases, the developers return to go through the same cycle once more. The different phases can be reviewed in-house or by a client representative.

The pros and cons of the Spiral Model

So – what are the key advantages and disadvantages of using the Spiral model for a software project? Let’s take a look at some of the most important aspects.

The pros

  • Highly flexible model
  • Fast and cost-effective development
  • Well-suited for large scale projects and mission-critical developments
  • Works well for complex projects
  • Monitoring is easy and effective
  • Strong emphasis on client approval
  • Focus on documentation control
  • Potential for additional post-project functionality
  • Software is produced early on in the project lifecycle
  • Risk analysis helps to eliminate and avoid risk
  • Changed requirements are accommodated during the project lifespan
  • The end product can be highly customised

The cons

  • Can be expensive to implement – especially if spirals continue infinitely
  • The risk analysis aspect of the project may require specialist expertise
  • Not an ideal fit for smaller or low-risk projects
  • Success may depend greatly on the risk analysis
  • Documentation can be heavy, due to the number of intermediate stages
  • End of project may be difficult to define beforehand
  • Spiral is widely regarded as a complex process
  • Rules and protocols must be adhered to strictly throughout the development

The conclusion

It may not be immediately obvious when the Spiral model is appropriate, but it will typically work best in medium to high-risk projects. It can be an option when users are unsure of their needs, as the prototype solution can help them understand the end product and its advantages. It does however generally require long-term commitment from all stakeholders as new, significant and complex change requirements may be discovered during the course of the project.

Not sure if Spiral development is suitable for your business? We can help you evaluate the approach which would bring the best benefit to your development project. Contact us today for an initial consultation!