Spiral Model in SDLC Methodology

Instructor: Joseph Moore

Joseph is an Adjunct Faculty member. He has a Ph.D. in Public Policy and Administration.

In this lesson, we will examine the spiral model in the Software Development Life Cycle. We will also discuss and review the four phases associated with the spiral model.

Spiral Model

The spiral model is a systems development life cycle model utilized when project managers are working on a software project. So what is a systems development life cycle model? A system development life cycle model is the actual process utilized for planning, creating, testing, and deploying an information system. The spiral model is one model that may be used when working on a project in information technology. So if you are a project manager and working on a complex and expensive software project for a company, this model may be used.

Why use the spiral model? If the project is high risk, complicated or you want to closely evaluate any issues that may arise throughout the process and at the earliest stages possible, then the spiral model is the best choice. Additionally, if a customer is unsure of what is needed in the software, this model is best to obtain customer feedback throughout the process.

The spiral model is a step-by-step process that a team should use if the focus is on risk management when working on a software project. The best way to think of the spiral model is to imagine a notebook that has four wire spirals. Think of each spiral as representing a goal within the project. Each spiral must go through all four phases to move to the next spiral. Once the first goal of the project is done and you have gone through all four phases of the spiral model, you will then start with the next goal of the project. The next goal will then go through the four phases as well: planning phase, risk analysis, developmental phase, and the evaluation phase.

Planning Phase

In the planning phase, it is important to get an understanding of the customer's requirements for the software project. The project manager can then better facilitate the software based on the needs of the customer, and if the requirements are not gathered correctly, this can cause tremendous delays and issues with the project. With the spiral model, it is important to note that the planning phase must be completed before moving on to the next phase.

Risk Analysis Phase

In the risk analysis phase, the software team examines the project and software to determine the potential for any issues or predicaments. For example, if a police department was contemplating allowing citizens to ride along and observe police officers while on duty, a risk analysis may be done. The police department may discuss the risk of having citizens ride along, and these risks may be the potential for accidents, injuries, or other factors that may arise.

If an issue is identified in the risk analysis phase, it is important to have strategies on how to handle these predicaments. It is important for all applicable project managers and personnel to identify the risks that may be encountered with the software. In this stage, if a risk is identified, then strategies and solutions are discussed to mitigate these potential risks.

Developmental Phase

The developmental phase is exactly what it says. In this phase, you develop the software. As we have discussed, in the spiral model customer feedback is important. Based on the customer's feedback throughout the different phases, this will be of great assistance when the software is developed.

Let's say that you work in a factory manufacturing vehicles. After all of the components of the vehicle are put together -- such as the engine, doors, tires, and the other applicable parts -- the vehicle is now ready to be driven. This is an example of how the developmental phase works -- during this phase you put together and develop what is needed in the software for it to subsequently start being used.

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