Agile, Scrum and Waterfall Software Development: What’s the Difference?

May 25, 2018 - by Brijmohan Bhavsar

Software development methodologies in the market today are aplenty: some improve process efficiency, while some minimize risk, some offer immense scalability while some focus on continuous iterations. But how do you know which one is the best for you? Let’s look at three popular software development methodologies – waterfall, agile and scrum – in detail, and see which one would serve your business needs best.

Overview

Waterfall	Agile	Scrum
Waterfall model is the earliest approach that was used for software development, and is today considered a traditional, time-tested approach in which distinct goals are accomplished. Incorporating a sequential design process in which progress is seen as flowing steadily downwards (like a waterfall), the waterfall method consists of a series of phases: conception, initiation, analysis, design, construction, testing, production/implementation and maintenance.	Agile is a time boxed, iterative approach to software delivery that builds software incrementally from the start of the project, instead of trying to deliver it all at once near the end. Almost three-quarters (71%) of organizations report using Agile approaches sometimes, often, or always.	Scrum, a subset of Agile, is a lightweight process framework for software development, and the most widely-used one. Like Agile, it uses an incremental approach to work in order to complete projects more quickly.

Benefits

Waterfall	Agile	Scrum
Phases are processed and completed one at a time and they do not overlap. Works well where requirements are very well understood The linear nature of this method makes it easy to understand and manage. Projects with clear objectives and stable requirements can best use the waterfall method. Less experienced project managers, project teams, and teams whose composition changes frequently may benefit the most from using the waterfall development methodology.	Reduces waste by focusing development efforts on high-value features and reducing time-to-market Team members enjoy development work and like to see their work used and valued Increases the quality of the deliverables Enhances customer satisfaction by rapid, continuous delivery of working software People and interactions are emphasized rather than processes and tools – customers, developers and testers constantly interact with each other There is a possibility to introduce and implement last minute changes	The sprint process allows for development that results in a saleable product even while the project is in full swing As each completed backlog represents a new release of the product, the incremental delivery system shortens the time to market and may result in higher revenue Reviewing each sprint before moving to the next means that testing is conducted throughout the process, which allows teams to change the scope or direction of the project at any point New changes can be implemented at very little cost because of the frequency of new increments that are produced Unlike the waterfall model, very limited planning is required to get started with the project

Challenges

Waterfall	Agile	Scrum
Each phase must be 100% complete before moving onto the next phase, and traditionally there is no process for going back to modify the project or direction Can’t handle change – Once an application is in the testing stage, it is very difficult to go back and change something that was not well-thought out in the concept stage Risk is high – As working software isn’t produced until the end of the project, you never really know where you are on a Waterfall project. That last 20% of the project always seems to take 80% of the time Not a good model for complex projects Slow and costly due to the rigid structure and tight controls Not suitable for the projects where requirements are at a moderate to high risk of changing	There is lack of emphasis on necessary designing and documentation Only senior programmers are capable of taking the kind of decisions required during the development process; for inexperienced programmers, the model is difficult to use The potential for scope creep is high that can lead to never-ending projects Testers are needed throughout the project and this effectively increases the cost of resources on the project Developers need to complete each feature 100% within each iteration, and the relentlessness of iterations can be mentally quite tiring Effort assessment is difficult	Adopting the Scrum framework in large teams is challenging The chances of project failure are high if individuals aren’t very committed or cooperative There is an adverse impact if a team member leaves midway.

Best Practices

Waterfall	Agile	Scrum
Projects are fairly simple Objectives are clear and concise Technology is understood There are no ambiguous requirements Resources with expertise are readily available	Frequency of changes is high New features need to be introduced regularly Customer wants to see a working product at regular intervals/li> Members of the development team are completely dedicated to the project	Project requirements are dynamic A quick feedback loop is required Changes are frequent/li> There is a qualified, cross-functional team in place Complex projects have to be completed in a short timeframe

Choosing What Fits

In the world of software development, choosing the right methodology is crucial to ensuring the success of your software. If the requirements of your project are clearly defined and the likelihood of changes are next to nil, the waterfall method with sequential steps will be ideal. However, if your project is large, with changes that happen frequently, agile method will enable you to bring your project to life in the most efficient manner. And if you have a cross-functional team in place that has the expertise to complete a dynamic project within a short time frame, go for the scrum method. Since each method has its own pros and cons, carefully analyzing them to see which one best fits your needs is vital.

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