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Agile vs Waterfall: Must-Know Differences
The success of a software development project is closely tied to the chosen development approach. Agile and Waterfall are two of the most popular SDLC methodologies in the present. As such, development teams might find themselves asking the question, which one to choose?
Both Agile and Waterfall methodologies are mature approaches to software development. Although the two share a few similarities, both SDLC models are different in several aspects. So, one should keep these in mind while making the pick amongst them.
Before setting out to explore the various dissimilarities between Agile and Waterfall methodologies, first, let us take a closer look at what they are and what are their strengths and weaknesses.
The Agile methodology of software development focuses on a continuous iteration of development and testing during the entire software development process. The SDLC model increases communication among clients, developers, and testers.
Scott Ambler started developing the Agile methodology during the autumn of 2000. Though initially dubbed Extreme Modelling (XM), it was later renamed Agile Modelling at the suggestion made by Robert Cecil Martin.
The Agile approach is an iterative and team-based approach to software development. It is a distinct type of the Rapid Application Development (RAD) model. Though not new, it is relatively newer when compared to the classic Waterfall model.
Instead of creating schedules and tasks, the entire time available for an Agile project is divided, time-boxed, into phases called sprints. Every sprint features a defined duration, typically, in weeks, with a list of deliverables that were planned during the start of the sprint.
Each of the deliverables is prioritized in terms of the business value which is determined by none other than the client(s). The Agile methodology relies greatly on a high level of customer involvement throughout the entire software development process.
In case the planned work for a particular sprint can’t be completed for some reason(s), the entire work is reprioritized while the information gained is used for upcoming sprint planning.
The completed work is evaluated and reviewed by both the project development team and the client. This is done through daily builds as well as end-of-sprint demos.
- As a client-focused process, it ensures that the client is involved continuously throughout the entire process, at every stage
- Assures that the quality of the software development is maintained to a desirable degree or even better
- Client(s) enjoys early and frequent opportunities to see the progress. Hence, it is possible to alter decisions throughout the project development process
- Imparts a strong sense of ownership to the client(s) as they are directly and extensively in contact with the project development team
- It can produce a basic version of the software under development that can be built upon in succeeding iterations. This is very helpful for projects where time to market the same is a concern of great importance
- Likely to produce better results. This is so because more often than not, Agile teams are exceptionally motivated and self-organized
- Reduced risk of failure as the process is completely based on incremental progress. Hence, both the client(s) and the development team know what is complete and what is not in an exact manner
- In case the project supervisor is uncertain about the outcome, there is a heightened risk of project derailment
- Necessitates the involvement of an expert for making vital decisions
- Not suitable for small-scale projects
- The overall cost of implementing an agile approach is slightly pricier than other software development approaches. Also, the total projected time might increase as the software development progresses
- The characteristic very high client involvement might not be what some clients might ask for
Also known as the traditional approach to software development, the Waterfall model follows a linear approach to software development. Because of this, it is also known as the Linear-Sequential Life Cycle Model.
The first formal description of the Waterfall model, although deprived of the word Waterfall, is cited to be a 1970 article by Winston W. Royce. The 1976 paper by Bell and Thayer is believed to feature the term Waterfall for the very first time.
Because the Waterfall model follows a strict sequential order, the project development team is able to move to the next phase only when the previous phase achieves successful completion. Usually, there is a stage-gate between each phase of the Waterfall approach.
- Advantageous for managing dependencies
- Client involvement isn’t mandatory for all phases of the software development
- Depending on the ongoing phase of the project, it is possible for different members of the team to focus on different tasks
- Each phase has distinct deliverables and a review process. Hence, it is easy to manage
- Has an easily adaptable approach for shifting teams
- Offers faster delivery of the product
- Planning and designing is straightforward as the client and development team agrees early about what and how of the software product under development
- Progress can be easily evaluated and measured because the full scope of the task is known beforehand
- Provides a software design with lessened chances of the piecemeal effect. This is due to the fact that the software is designed more carefully and completely from the very beginning
- Suitable for projects where there is a need for multiple software components to be designed for integration with some external system
- Well documented process and results
- Works exceptionally well for small-scale projects, especially those with easily understandable requirements
- High chances of bugs and vulnerabilities as the testing process starts only when the project development is over
- Impractical for large-scale projects
- Incapable to accommodate changes made later during the process
- Less effective method when the requirements aren’t clear at the beginning
- Presents an unclear picture of what the client(s) can expect as the end product
Agile vs Waterfall: The Face-Off!
Degree of Flexibility
The Waterfall model is a structured software development methodology. As it is incapable of accommodating later changes, it offers a little to no flexibility. On the other end, one of the primary reasons for preferring the Agile approach is its high degree of flexibility.
The Agile methodology allows for changes to be made in the project requirements even after the initial planning is completed. The Waterfall model has no provision for changing requirements once the project development starts.
Division of the Entire Process
The Agile methodology divides the entire development lifecycle into sprints. On the contrary, the Waterfall approach has the same divided into distinct phases.
Funding and Resources Preference
As the risk agreement is made at the very beginning of the software development process, the Waterfall methodology reduces the overall risk in a fixed-price project.
The Agile model doesn’t favor for fixed-price projects. Instead, fixed-price scenarios might increase stress over an Agile project. The Agile methodology is best suited for projects with non-fixed or Time & Materials (T&M) type of funding.
Occurrence of Phases
As the Agile model follows an iterative mode of development, various phases like planning, development, and prototyping may appear more than once during the entire run of the software development process.
In the Waterfall approach of software development, all phases appear once and only once during the entire process.
Preparation of Requirements
In order to come up with the requirements for the software project to be developed, an extensive business analysis needs to be performed for following a Waterfall approach. There is no involvement of the development team members in recognizing the project requirements.
Following the Agile approach, both the client(s), as well as the development team, sit together almost every day to prepare project requirements. As such, the testing team can also participate in changing requirements.
The primary focus of the Waterfall approach is accomplishing a product. The Agile model has a primary focus of gaining product satisfaction from the client as well as changing itself as per the evolving or newer customer needs.
Project Details Description
It is possible to alter the project details description at any time during the entire software development process following the Agile approach.
This is not the case with the Waterfall model where there is no provision for changing project details description once the project development kicks-off.
With the Waterfall approach, a software development project is viewed as a single project. This is in sharp contrast to the Agile methodology, which treats the software project under development as a number of different sub-projects.
Team coordination or synchronization is very limited in the Waterfall approach. There is no preference for team size. On the contrary, the Agile model prefers a small but dedicated team. Hence, the degree of coordination amongst its members is very high.
The team members of an Agile team are interchangeable. Hence, they work faster. Moreover, the software development approach discards the need for project managers as the entire team is responsible for managing the software project under development.
The project manager is the one responsible for having the final say during all phases of the software development following the Waterfall approach. Moreover, the interchangeability of team members is not possible.
The Waterfall methodology has a dedicated Testing phase that comes only after when the Development phase achieves successful completion. In the Agile approach, testing is done simultaneously with software development.
Also, the test plan is seldom reviewed during the test phase of the Waterfall model. Unlike this, the test plan pertaining to an Agile project is reviewed after each sprint.
Type of Requirements
Requirements pertaining to a Waterfall methodology are definite, which means any change regarding the same is unexpected.
On the flip side, any project whose requirements are expected to change or evolve during the software development process is considered ideal for Agile development.
Way of Approaching
The Agile model follows an incremental approach to software development. Additions to the software under development are made in increments and it is possible to jump between different parts of the software development process.
Waterfall methodology, on the other hand, follows a sequential design process. Moving on to the next phase of the development process is only possible when the previous phase has been completed successfully.
The Agile and Waterfall methodologies are distinct forms of software development methodologies. Hence, each of them is great in some scenarios while impractical in others.
Software development projects that have evolving or uncertain requirements are ideal to be completed using the Agile methodology. Contrarily, smaller software development projects with definite requirements find the Waterfall model to be the best pick.
We hope that the aforementioned comparison will make it easy for you to make a selection among the two popular SDLC models. Wish you all the very best for your software project development.
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