6 Basic SDLC Methodologies: Which One is Best?

SDLC methodologies: Pretend Agile Waterfall is a "thing."

A wise man once said that if you fail to plan, you plan to fail (and, no, it wasn’t Homer Simpson). The Systems Development Life Cycle (SDLC) gives structure to the madness of getting from the beginning to the end of your project without forgetting a step.

It’s a type of project plan, and a number of different SDLC methodologies are used today to guide your way through projects.

Here are the key pros and cons of six of the most common SDLC methodologies.

1. Waterfall Model

Waterfall is the oldest and most straightforward of the structured SDLC methodologies — finish one phase, then move on to the next. No going back. Each stage relies on information from the previous stage and has its own project plan. Waterfall is easy to understand and simple to manage. But early delays can throw off the entire project timeline. And since there is little room for revisions once a stage is completed, problems can’t be fixed until you get to the maintenance stage. This model doesn’t work well if flexibility is needed or if the project is long term and ongoing.

2. V-Shaped Model

Also known as the Verification and Validation model, the V-shaped model grew out of Waterfall and is characterized by a corresponding testing phase for each development stage. Like Waterfall, each stage begins only after the previous one has ended. This model is useful when there are no unknown requirements, as it’s still difficult to go back and make changes.

3. Iterative Model

The Iterative model is repetition incarnate. Instead of starting with fully known requirements, you implement a set of software requirements, then test, evaluate and pinpoint further requirements. A new version of the software is produced with each phase, or iteration. Rinse and repeat until the complete system is ready.

One advantage over other SDLC methodologies: This model gives you a working version early in the process and makes it less expensive to implement changes. One disadvantage: Resources can quickly be eaten up by repeating the process again and again.

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4. Spiral Model

One of the most flexible SDLC methodologies, the Spiral model takes a cue from the Iterative model and its repetition; the project passes through four phases over and over in a “spiral” until completed, allowing for multiple rounds of refinement. This model allows for the building of a highly customized product, and user feedback can be incorporated from early on in the project. But the risk you run is creating a never-ending spiral for a project that goes on and on.

5. Big Bang Model

A bit of an anomaly among SDLC methodologies, the Big Bang model follows no specific process, and very little time is spent on planning. The majority of resources are thrown toward development, and even the client may not have a solid grasp of the requirements. This is one of the SDLC methodologies typically used for small projects with only one or two software engineers.

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Big Bang is not recommended for large or complex projects, as it’s a high-risk model; if the requirements are misunderstood in the beginning, you could get to the end and realize the project may have to be started all over again.

6. Agile Model

By breaking the product into cycles, the Agile model quickly delivers a working product and is considered a very realistic development approach. The model produces ongoing releases, each with small, incremental changes from the previous release. At each iteration, the product is tested.

This model emphasizes interaction, as the customers, developers and testers work together throughout the project. But since this model depends heavily on customer interaction, the project can head the wrong way if the customer is not clear on the direction he or she wants to go.

More Resources on Agile and Waterfall methodologies: