Waterfall vs. Agile: A Comparison of Methodologies

Written by Wholegrain Team - September 3, 2014

Like so many things in life, there is more than one way to develop software, and each method has its pros and cons. Two of the most common approaches are Waterfall and Agile, and both methodologies have their passionate backers and their keen detractors.

When it comes to software development, or indeed any kind of project management, the success of your project starts well before the work gets underway. It begins with planning, and with choosing the most effective framework for your particular project.

For your benefit, we’ve put together this useful comparison to help you understand the differences between Waterfall and Agile, and decide which approach would work best for your project.

The Waterfall Methodology

The Waterfall method is an old and time-proven development framework that’s been in use since the 1970s, and has been the driving force behind a huge number of systems. It’s a classically linear model of software design, and development flows sequentially from the start point through to the end point, much as its name suggests.

The Waterfall method originated from the standard workflow process used in the manufacturing and construction industries, and the lifecycle of the project follows a very structured, stage-by-stage approach. Typically, this involves conception, initiation, analysis, design, construction, testing, implementation, and maintenance.

Because the process is sequential, it’s largely inflexible – once a stage has been completed, it’s difficult to go back to a previous step without scrapping the entire process and starting afresh. Because of this, it requires comprehensive planning from the outset because there is little margin for error.

The Pros and Cons of Waterfall

Because the Waterfall method requires extensive planning from the outset, both the developer and the client agree on the desired outcome at an early stage, so it’s fairly straightforward to estimate the project in terms of timescale and budget. Progress is easy to measure and the meticulous records give you the means to improve on the existing programme in the future.

The thorough documentation also makes projects more secure. If a developer drops out during the process, for example, a new developer can step in fairly easily because the project notes are so detailed.

However, this approach does have its disadvantages, the main one being its rigidity and inflexibility. Once water has flowed over the edge of a waterfall, there is no way for it to return, and this method has a similar  problem. Once a stage has been completed, it’s difficult to go back and make changes. Which is why it requires such extensive planning from the outset.

This rigid structure means that if one of the original requirements is found to be faulty, the project has to start over. In addition, testing takes place in one of the final stages, so if a bug has been written at the start there is a greater chance it has become deeply embedded in the programme, affecting latter stages and making it costly and time-consuming to correct.

Finally, the Waterfall method is problematic as it doesn’t account for a client’s evolving needs. What’s more, because the deliverables are based on the initial requirements, the client may not see the project until towards the end. And if they don’t like it, change will be difficult and expensive.

The Agile Methodology

The Agile method is a more recent development framework, designed as a solution to the disadvantages of the Waterfall method. Instead of a sequential design process, it follows an incremental, iterative approach with a strong focus on collaboration and teamwork.

Developers start with a basic project design, but there is no predetermined course or plan to follow. Instead, the designers work on small modules in weekly or monthly sprints. At the end of each sprint, the project priorities are discussed and tested, before being reviewed and evaluated by the client.

This method is much more flexible. Bugs are picked up at the end of each stage and corrected, and the client’s evolving needs can be incorporated before moving on to the next sprint.

The Pros and Cons of Agile

The biggest benefit of Agile is its flexibility. Because the work is carried out in small sprints, there is potential for change to be implemented after the initial planning stage.

The client is involved throughout the process so they have the opportunity to identify anything they don’t like, or introduce new elements to keep the project up to date with any new developments in their field.

Because testing is carried out at the end of each sprint, there is also a greater chance of identifying any potential bugs and filtering them out before they become embedded in the programme.

The Agile process is especially useful in situations where clients have only a vague, hazy idea of their end goal – as the project progresses and the client can see different elements in action they can help shape it to their exact requirements.

It does, however, have its disadvantages. To have the maximum effect, Agile requires close communication with the client, and some clients are not able to commit to this. Likewise, it works best if the developers stick with the project to its conclusion – if somebody drops out during the process it can be difficult for another developer to step into their shoes.

Because the project doesn’t have a strong identity from the outset, the finished project can end up totally different from what was intended and it can be more difficult to accurately predict the timescale and budget. It also requires a competent project manager and a team firmly committed to collaboration and teamwork.

Which Method is the Best?

Both Waterfall and Agile methodologies have their advantages and disadvantages, but which will be the best for you? Well, it depends upon your requirements. If you have a structured, static project, with a clearly defined goal and requirements that will not change, plus little opportunity for interaction between developer and client, then Waterfall is best as a model of predictability.

However, the keyword for Agile is adaptability. If you have a project with a hazy end goal, where the needs and requirements of the project are fluid, or where the business environment is uncertain, then Agile is the way forward. The Agile approach allows you to make frequent changes, and because you test the project at each stage there is a much better change of a successful outcome. This modern, collaborative process does require a skilled team of developers with excellent communication skills and a strong ethic for teamwork, but its flexibility and strong success rate means an increasing number of companies see Agile as the future.

Do you use the Waterfall or Agile development framework? What do you think are the main strengths and weaknesses of each? Tell us below…