The Software Development Life Cycle (SDLC) is the process of planning, designing, building, testing, and deploying software efficiently while minimizing costs and timelines. Choosing the right software development model is crucial to meeting your organization’s needs, stakeholder expectations, and project goals.
Each model has its own strengths and weaknesses, and the choice should align with your project’s scope, timeline, and budget. Picking the wrong model can lead to delays, budget overruns, poor-quality software, or even total project failure.
Let’s dive into seven popular software development models and how they impact project success.
1. Waterfall Model
The Waterfall model is one of the oldest and simplest approaches to software development. It follows a linear, step-by-step process: analysis, design, development, testing, deployment, and maintenance. Each phase must be completed before moving on to the next.
Pros & Cons of the Waterfall Model
The Waterfall model is straightforward and easy to follow. Every stage has clear deliverables and milestones, ensuring progress is measurable.
However, it lacks flexibility. Once a phase is complete, there’s no going back or overlapping stages. If you identify errors later in the process, you’ll need to wait until the maintenance stage to address them. This rigidity makes adjustments difficult and costly.
This model is risky if project requirements are unclear or prone to change. It’s also not suitable for long-term, complex projects that demand adaptability.
That said, the Waterfall model can be useful for small, one-time projects with well-defined and fixed requirements. For such cases, its simplicity can lead to faster results. However, as the software industry shifts towards more agile and flexible approaches, the Waterfall model has declined in popularity.
2. V-Model (Validation & Verification Model)
The V-Model is an extension of the Waterfall model that incorporates early testing into the development process. It follows a similar linear structure but takes a “V” shape, with development stages descending on one side and corresponding testing stages ascending on the other.
Pros & Cons of the V-Model
The main advantage of the V-Model is that testing begins early. Every development stage has a paired testing activity, helping teams catch errors in requirements, architecture, and code before moving forward. This increases the chances of project success compared to the Waterfall model.
Despite this improvement, the V-Model is still rigid and linear. Like the Waterfall model, teams must complete each stage before starting the next, making it difficult and expensive to make adjustments once the project is underway.
The V-Model works best for short projects with well-documented, fixed requirements. However, it’s not ideal for long-term, evolving, or complex projects where flexibility is essential.
3. Iterative (and Incremental) Model
The Iterative (and Incremental) model was created to address the limitations of the Waterfall model. Like Waterfall, it starts with planning and ends with deployment. However, the key difference is that this model includes repeated cycles throughout the development process.
As the name implies, the cycles are iterative (repeated) and incremental (happening in short bursts).
Development begins with a small set of requirements, and with each new cycle, new requirements are added.
Pros & Cons of the Iterative Model
The iterative nature allows the software to evolve over time. Small adjustments can be made based on feedback from previous cycles. This means developers can refine the product continuously, improving it after each iteration.
Since all requirements aren’t fixed at the beginning, work can begin quickly. However, because the process is repeated frequently, resources may be drained faster, and managing the process can become more complex.
Although the model allows for some changes, it still operates within a set framework. This can result in some inflexibility. Even though changes are less costly than in the Waterfall or V-Model, this approach is still not ideal for projects where requirements change frequently during iterations.
The Iterative model can introduce risks with frequent changes, uncertain costs, unpredictable resource needs, and unclear deadlines.
4. Prototyping Model
The Prototyping model focuses on improving the development team’s understanding of customer needs by creating prototypes. Instead of jumping straight into the final product, a small-scale version of the software is built first, allowing the team to refine the design based on feedback before development starts.
Once the prototype is built, it is tested and refined until the customer approves it. After this, the team begins working on the final product.
Pros & Cons of the Prototyping Model
The Prototyping model can greatly reduce the number of iterations needed in the SDLC due to the early feedback from the customer. This feedback helps ensure the final product is more aligned with customer expectations, increasing satisfaction and saving time.
However, the time spent developing prototypes can add up. If the customer frequently changes their mind or makes unrealistic requests, it can lead to excessive iterations, causing delays. To avoid this, it’s best to limit the number of iterations allowed before the prototype is accepted.
Once the final prototype is being developed, no further changes to the requirements can be made. This inflexibility is a significant drawback of the Prototyping model.
5. Spiral Model
The Spiral Model emphasizes risk management and is best suited for teams with expertise in risk assessment. It consists of four phases: planning, risk analysis, engineering, and evaluation. The number of loops or iterations in the spiral depends on the specific project and the project manager’s discretion.
This model blends features of the Waterfall and Prototyping models, focusing on design and incorporating prototyping in the engineering phase. It follows similar phases to Waterfall while also allowing for more flexibility.
Pros & Cons of the Spiral Model
The Spiral model’s continuous development allows for changes and the addition of new features while carefully managing risks. The process is systematic, making development more streamlined.
However, customer involvement at each stage can slow down the development process, especially if feedback is delayed. Customer changes are not permitted during the engineering phase, which can lead to frustration if the customer wants modifications after that point.
Since the number of loops is not fixed, there is a risk of going over budget or missing deadlines. Achieving the final product can be costly and time-consuming.
Moreover, the Spiral model is highly customized for each project, meaning the work cannot be reused for future projects.
Agile Methodology Development Models
Agile is a mindset, not just a set of strict protocols, based on the 12 principles outlined in the Agile Manifesto. It was developed to improve software delivery by focusing on collaboration, communication, and continuous change, making it more effective and efficient than traditional methodologies like Waterfall.
Agile has gained widespread adoption. According to the Project Management Institute, 71% of organizations report using Agile approaches either sometimes, often, or always in their projects.
Agile methodologies emphasize teamwork, cross-functional collaboration, iterative development, and early customer feedback. By testing, gathering feedback, and making adjustments throughout the development cycle, Agile teams aim to deliver the best software.
Let’s dive into two of the most popular Agile development models.
6. Scrum Model
The Scrum model is the most widely used Agile model. It organizes development into iterations known as sprints, typically lasting between 1 and 4 weeks. During each sprint, the team reviews the previous sprint, adds new features, and plans for the next sprint. Once a sprint’s activities are defined, no changes are allowed until the next sprint.
After each sprint, new features are added, tested, and refined in subsequent sprints until all features are completed and the project is ready for release.
Scrum Model Advantages & Disadvantages
Advantages:
- Increased collaboration between cross-functional teams and with customers helps reduce errors that arise from poor communication.
- The incremental nature of Scrum reduces the time to market for the software, delivering value faster.
- Enhanced communication minimizes the time spent on error resolution and increases customer satisfaction with the product.
Disadvantages:
- Scrum requires a significant input of time and effort from customers throughout the process, which can be demanding.
- Adding too many features or making frequent changes during sprints can push deadlines back, delaying the final product.
7. Kanban Model
The Kanban model is another Agile methodology but is quite different from others due to its lack of pronounced iterations. If any iterations occur, they tend to be very short, sometimes lasting only a single day.
Teams using Kanban typically rely on a Kanban board to visually represent the project’s progress. The board includes sticky notes that represent tasks, with details like project owners and the current status of each task. This visualization helps the team focus on the most important feature at any given time and see opportunities for continual improvement.
Kanban Model Advantages & Disadvantages
Advantages:
- The Kanban board encourages focus on the task at hand, helping the team refine features effectively.
- The flexibility of the model allows changes to be made at any time, which can be beneficial when adapting to evolving requirements.
Disadvantages:
- Without defined timeframes, planning long-term projects can be challenging. The visual representation on the board is useful for task focus but doesn’t provide the structure needed for comprehensive time management.
- The constant potential for changes without defined planning stages can lead to inefficiencies and make it difficult to meet deadlines.
The Shift to Agile Software Development
Each software development model was created to improve the delivery process. Today, each model serves specific types of projects well, but older models like Waterfall are becoming less common.
In today’s fast-paced IT landscape, teams and businesses need to be quicker, more efficient, and capable of delivering software faster while keeping up with competition. A more repeatable and secure development process relies on automation, which many older models, including Waterfall, cannot support at the necessary speed.
This need for speed and automation has fueled the rise of Agile, which is well-suited to meet these demands. As a result, organizations are adopting technologies and practices like continuous integration (CI), continuous delivery (CD), release automation, and DevOps to further enhance their development processes.
