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Agile vs Waterfall: Differences You Should Know
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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 at 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 pitting Agile vs Waterfall and setting out to explore the various dissimilarities between the two, first, let us take a closer look at what they are, then assess their strengths and weaknesses.
What is Agile Methodology? [Definition]
The Agile software development methodology 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 in 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 more recent 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 significantly on a high level of customer involvement throughout the entire software development process.
If 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 entirely 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
- It 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
Which Organizations Use Agile?
There are many big companies using the Agile method, such as IBM, Apple, Procter & Gamble, and even Microsoft. However, big tech companies aren’t the only ones who can use Agile. Many fields can get some great use out of this method, including the aerospace, pharmaceutical, engineering, construction management, and content management industries. Businesses of any size can use this method, so even if you are a three-person team, Agile can work for you.
What is Waterfall Methodology?
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.
Although derived from the word Waterfall, the first formal description of the Waterfall model is cited in 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 strictly sequential order, the project development team can 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, different members of the team can 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 are straightforward as the client and development team agrees early about what and how of the software product under development
- Progress can be quickly 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 because the software is designed more carefully and entirely 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 of accommodating 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
Comparing Agile vs Waterfall Project Management
Which Organizations Use Waterfall?
Because of the linear nature of Waterfall (and its tendency for rigidity), it’s not always the best method for everyone. When considering the Waterfall model vs Agile, it’s important to look at the characteristics of your project to ensure the method’s suitability. Many industries continue to use this methodology to this day, including banking, construction, IT, and software development.
Agile vs Waterfall: Differences You Should Know
1. Degree of Flexibility
The Waterfall model is a structured software development methodology. As it is incapable of accommodating later changes, it offers 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 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.
2. 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.
3. 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 work well 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.
4. 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.
5. Preparation of Requirements
To come up with the requirements for the software project to be developed, extensive business analysis needs to be performed by 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) and the development team sit together almost daily to prepare project requirements. As such, the testing team can also participate in changing requirements.
6. Primary Focus
The primary focus of the Waterfall approach is accomplishing a product. The Agile model focuses on gaining product satisfaction from the client and changing itself as per the evolving or newer customer needs.
7. 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.
8. Project View
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 several sub-projects.
9. Team Coordination
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.
10. Team Interchangeability
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 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 of an Agile project is reviewed after each sprint.
12. Type of Requirements
Requirements of the Waterfall methodology is 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.
13. 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 step has been completed successfully.
Agile vs Waterfall: Head-to-Head Comparison
Segregation of development cycle
It separates the project development lifecycle into sprints.
The software development process is divided into distinct phases.
It follows an incremental approach.
This methodology is a sequential design process.
Flexible: requirements can be changed.
Rigid: requirements cannot be changed once the project development starts.
Test plan reviewal
Reviewed after each sprint
The test plan is rarely discussed during the test phase
Testing is performed along with software development.
The testing phase comes after the build phase.
It works well with Time & Materials or non-fixed funding. It may increase stress in fixed-price scenarios.
Reduces risk in the firm-fixed-price contracts by getting risk agreement at the beginning of the process.
A small team with dedicated people for a high degree of coordination and synchronization.
Team coordination/synchronization is very limited.
Product requirements are discussed every day during the project.
Business analysis prepares requirements before the beginning of the project
Description of project details can be altered anytime during the SDLC process.
Detail description needs to implement the waterfall software development approach.
The Agile Team members are interchangeable, as a result, they work faster. There is also no need for project managers because the projects are managed by the entire team
The process is always straightforward so, the project manager plays an essential role during every stage of SDLC.
Agile and Waterfall are distinct forms of software development methodologies. Hence, each of them is great in some scenarios while impractical in others. Software development projects with evolving or uncertain requirements are ideal to be completed using the Agile methodology. On the other hand, software development projects with definite requirements find the Waterfall model the best pick.
Choose Agile if you want more flexibility and collaboration on multiple sprints at once without the need for a dedicated manager. If you have a set timeline for a single project with pre-defined requirements, the Waterfall approach vs Agile might be better for you — even if you’ll need a project manager. And, if neither method feels right, remember that you can always combine them.
We hope that the comparison above will make it easy for you to make a selection among the two popular SDLC models. Wish you all the very best in your software project development.
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Frequently Asked Questions
1. What is the difference between Waterfall and Agile?
- Agile is an iterative process, while Waterfall uses a more traditional approach — a linear/sequential flow.
- Agile was created for projects that need more flexibility, while Waterfall works best for projects that have a rigid timeline with well-documented and understood requirements.
- Agile separates work within a project into “sprints,” short “time-boxed” periods within which a scrum team must complete the work. Teams can work on several sprints simultaneously. Waterfall, on the other hand, separates projects into phases, where one phase must be finished before another one is begun.
- Agile is best for teams working on many small projects at once, while Waterfall works better for teams working on single projects.
- Agile focuses on customer satisfaction. Waterfall focuses on the successful delivery of a software project.
- Agile methodologies can add requirements whenever they want and change them at any time. Waterfall methodologies establish requirements once prior to starting a project, then avoid any changes to the scope once the project has begun.
- Agile teams can operate without a dedicated manager, whereas Waterfall requires one.
2. Why Agile is preferred over Waterfall?
Teams worldwide choose the Agile method for many reasons, one being that this methodology is collaborative and best suits a flexible and self-motivated team. Here are some of the other reasons:
- Agile does not require a dedicated manager for a team to succeed.
- This flexible methodology leaves plenty of room for the team and project to adapt and change during the project development process. The extra room to change also allows the budget to be more flexible.
- Agile is better when the project(s) is somewhat more dependent on research and testing because adjustments can be made after every iteration.
- Agile works well for situations where owners and stakeholders might be more involved in the process, especially when they check infrequently.
Agile is great for teams that want to move quickly while still being able to experiment with the direction they’re taking their project in.
3. What is the difference between Agile and Waterfall testing?
Agile testing is not a separate phase. Teams perform testing alongside the development sprints, often performing a test during every iteration. The dev and testing teams work together every step of the way, and testers are also involved in creating the requirements in the methodology. Agile does regression and acceptance testing after every iteration, with no delays between the coding and testing. For this reason, different testing levels may overlap.
Teams perform Waterfall testing as a separate phase, different from the development process. In fact, no testing is done until development is completed. All types of testing, whether regression or acceptance, are performed after the dev phase is done. Devs and testers work separately, and testers are not at all involved in determining the requirements of the project. Time delays are expected between coding and testing, and testing phases do not overlap.
4. Can you mix Agile and Waterfall?
Yes! Many companies take the best parts of both methodologies and combine them into their own process. Google famously uses a mix of both.
The mix of both Agile and Waterfall is often called “Agifall” since it combines the best of both worlds by injecting some of Agile’s traits into a looser Waterfall-like process. The goal of Agifall is to decrease a project’s cost and improve its quality while managing to boost development speed.
Agile fall uses a user-centric planning process and succeeds by carrying the requirements and planning of Waterfall while using a more Agile-like approach. Using this combined method, teams don’t need to wait for one project phase to finish before they start another. Instead, the next phase begins as soon as possible. The result is an independent development of components and modules of the project even during the planning phase.
An excellent example of this is doing graphic design and testing at the same time as the dev phase.
5. Is Agile cheaper than Waterfall?
Not necessarily. It is a common myth or misunderstanding that Agile is cheaper or faster than Waterfall. There’s no doubt that this misunderstanding has contributed to Agile’s rapid growth in popularity, but it is not always the case.
Agile can be cheaper and faster than its counterpart. The caveat is that this only happens when Agile is the method more suited to the team and project. Waterfall has the same opportunity to be cheaper and faster in the right situations.