The Iterative Waterfall Model is an adaptation of the classical Waterfall Model in software development. Introduced as an improvement to Winston W. Royce's 1970 Waterfall Model, it retains the foundational structure of sequential phases while introducing feedback loops that allow for iteration throughout the development process. This methodology enables teams to manage predefined requirements while accommodating minor adjustments as projects progress, making it suitable for various industries that require both structure and controlled flexibility.
The model blends the predictability and structured nature of the classic Waterfall approach with the practical flexibility needed for real-world software development, addressing the rigidity challenges associated with its predecessor.
Publication Date: February 24, 2025
Reading Time: 5 minutes
The Waterfall Model is a traditional software development approach introduced by Winston W. Royce in 1970. It adopts a linear and sequential methodology with several phases that must be executed in a predetermined order. While this model appears straightforward and ideal in theory, it can be difficult to apply effectively in actual software development projects due to its inflexibility. This shortcoming led to the creation of the Iterative Waterfall Model, which includes essential modifications to improve usability and efficiency in practical applications.
The Waterfall Model follows a strict sequence of steps in software development with these main features:
Emphasis on Documentation: Detailed documentation is maintained at every stage, ensuring clear requirements and traceability.
Predefined Schedule: Each phase has a fixed timeline, helping projects stay on track and within budget.
Linear Structure: It follows a step-by-step approach, allowing developers to monitor progress and spot issues early.
High Discipline and Structure: Its rigid framework makes it ideal for projects with well-defined and stable requirements.
The classical Waterfall Model has several significant limitations:
Lack of Flexibility: Once a phase is completed, it is difficult to go back and make changes.
High Risk and Uncertainty: If requirements change later, it can lead to costly revisions.
No Working Software Until Late: The product is only available at the end, delaying user feedback.
Not Suitable for Complex Projects: It struggles with projects where requirements are likely to change.
Limited User Involvement: Users are involved mainly at the beginning and end, which reduces the chance for feedback during development.
The Iterative Waterfall Model is an adaptation of the classical Waterfall Model that addresses its primary limitations. While the classic waterfall model follows a very linear and stepwise approach through all phases (requirements, design, implementation, testing, and maintenance) one at a time, the Iterative Waterfall Model incorporates feedback loops between phases.
This model allows teams to revisit earlier phases when necessary. For example, if an error occurs or a requirement changes during the testing or deployment phases, the team can go back into earlier phases to implement the necessary fixes. This approach:
The Iterative Waterfall Model differs from pure Agile methodologies (referred to as "Waterfall Agile Iterative" in some contexts). While it benefits from a structured approach and schedule, it emphasizes iteration within a more controlled framework compared to Agile's continuous collaboration and frequent requirement changes.
This approach benefits projects whose requirements are mainly predefined but might need minor tweaks during development.
The Iterative Waterfall Model follows similar phases to the original Waterfall Model but includes feedback loops that allow revisiting prior phases when necessary. Each phase is described below:
The model consists of six primary phases:
Requirements Gathering: Collecting and documenting all user requirements to clearly define the project's scope. Changes are not allowed once this phase is completed.
Design: Creating system architecture and detailed design plans based on the requirements. This phase outlines how the software will work and look.
Implementation: Writing the actual code according to the design specifications. Developers build and integrate each module to form the complete system.
Testing: Verifying and validating the software to find and fix bugs. This ensures the product meets all requirements and functions correctly.
Deployment: Releasing the finished product to the users. It involves installation, configuration, and making the system live.
Review and Improvement: Evaluating the project's success and identifying lessons learned. Feedback is documented for future projects but no changes are made to the current product.
The first phase involves gathering and analysing requirements. The project team consults with key stakeholders to define the software project's functional and non-functional requirements. All requirements are well-documented and used throughout the entire project.
Iterative Aspect: This model offers the unique ability to revisit this phase. If gaps and ambiguities within the requirements are later identified, the team may return to this discussion phase and correct some parts to meet stakeholder expectations.
Requirements are translated into a detailed system design. This outlines the data flow, database structures, user interfaces, and system architecture. The system design acts as a blueprint for development processes.
Iterative Aspect: The design can be refined if problems occur during implementation or testing. This flexibility reduces the risk of delivering a suboptimal product.
Developers develop the software's code following the design specifications. This includes programming, module integration, and developing the system's core functionality.
Iterative Aspect: If problems arise during coding a specific feature, the team should correct them from the design stage. This ensures the software is done efficiently and effectively.
The testing phase is critical in the Iterative Waterfall Model. The software is extensively tested against bugs, errors, and usability glitches. Testing is completed by ensuring that the software meets the requirements set in the initial phases.
Iterative Aspect: If a bug is discovered at the testing phase and has a root cause that started at the design phase, the team can return to the design phase and fix the problem. This feedback loop improves the overall quality of the software.
The software is finally deployed to the production environment following rigorous testing and validation. In the Iterative Waterfall Model, this deployment is usually followed by a short observation period for minor issues that may have arisen in the live environment.
The maintenance phase after deployment includes updates, fixing bugs, and optimising performance according to user feedback. Iteration is less frequent during this phase but still possible if significant changes or improvements are needed.
The following example demonstrates how the iterative nature of the model works in practice, showing how feedback leads to design refinement:
def add_numbers(a, b):
return a + b
# Initial test with positive numbers
result = add_numbers(5, 3)
print(f"Sum: {result}") # Output: Sum: 8
# After feedback, we modify the design to handle negative numbers
def add_numbers_v2(a, b):
if a < 0 or b < 0:
return f"Negative input: {a}, {b}"
return a + b
# Updated test
result = add_numbers_v2(-5, 3)
print(f"Sum with feedback: {result}") # Output: Negative input: -5, 3
Sum: 8
Sum with feedback: Negative input: -5, 3
This example illustrates the iterative process:
The Iterative Waterfall Model is popular among various industries and teams that must balance structure and flexibility. The main users include:
Teams working on projects with partially defined requirements will likely opt for the Waterfall Model. They can develop it in phases yet are open to minor changes during the development lifecycle.
Organisations with tight budgets or timelines prefer this model because it offers a predictable development process with the flexibility to make slight changes without entirely derailing the project.
Healthcare, finance, and government sectors demand strict compliance and documentation. The Waterfall Model meets these demands while providing the flexibility to fine-tune the product as necessary.
This model is often used in education to teach students about software development methodologies. The waterfall model provides a structured framework that is easy to understand while introducing the concept of iteration.
Some clients like methodologies that indicate the timeline and budget. The Waterfall Model has a structured approach to ensuring stakeholders understand what is going on with the project at any given time, but feedback loops help to control changes.
The Iterative Waterfall Model is suitable for projects with well-defined requirements, though they could need minor adaptations in the development process. The model is ideal for situations where initial feedback is required at the development stage to ascertain that the end product will meet expectations.
Industries such as healthcare, finance, and government typically utilise this model due to its significance in producing:
Ideal for Clear Objectives: Works best for projects with well-defined goals but requiring periodic validation and refinement.
Perfect for Software Development: Ensures functions are tested and reviewed iteratively, reducing defects.
Incorporates Feedback Loops: Allows teams to address faults and implement improvements before advancing.
Risk Mitigation Focus: Applied in projects where identifying and resolving risks early is crucial.
Prevents Major Issues: Revisiting earlier phases helps catch issues early, avoiding major problems later in the process.
If the client wants to provide feedback but likes structured predictability instead of waterfall iterative and agile flexibility, a Waterfall model is employed. This offers the rigidity and structure found in the traditional waterfall and combines them with some form of Agile flexibility. It works best in projects with:
Using the right software and tools is essential for accurate project management and tracking in the Waterfall Model. They help in planning, organizing, and monitoring each phase in a structured way. With tools, it's possible to keep the project on schedule and meet all requirements.
Gantt charts are essential tools in the Waterfall Model for tracking project timelines. They visually represent:
This helps project managers monitor progress, identify delays, and adjust schedules if needed. With Gantt charts, teams can clearly see which tasks are completed and what's coming up next, keeping the project organised and on track.
Project management software is often used in the waterfall model to:
Using the right software makes a significant difference in control and efficient project management.
The Waterfall Model falls between the classic Waterfall Model and more flexible methodologies such as waterfall agile iterative. Because of its structured approach and feedback loops, this model is well-suited for projects that demand high-quality deliverables and some adaptability. However, like every model, it has advantages and disadvantages that should be carefully considered before implementation.
Feedback loops allow teams to correct errors or refine designs in earlier phases, reducing the likelihood of encountering major issues later in development.
The model provides a clear outline of development steps that ensure completion in sequence with controlled iterations. It therefore allows predictability and moderate accommodation of requirement changes.
The model ensures higher-quality deliverables by enabling iterative testing and refinement. Potential defects are identified early in the process and resolved before final delivery.
Each phase requires detailed documentation, which is very beneficial for regulated industries such as healthcare or finance, where compliance and traceability are critical.
This model's iterative nature allows assessment of project risk at each phase, reducing the chances of failure.
It accommodates a degree of flexibility and is therefore unsuitable for projects with fluctuating or not well-defined requirements, in which case waterfall iterative and agile methodologies would be better.
Reviewing earlier stages due to feedback loops can increase the timeline and cost, depending on when the problems arise in the development process.
Managing iterations with structured phases complicates project management, demanding a skilled team and clear communication to avoid delay.
Documentation is helpful but usually time-consuming and resource-intensive for small or fast-paced projects.
The Iterative Waterfall Model combines the strengths of the traditional Waterfall Model with the flexibility offered by Agile in the form of iterations. For that reason, it is one of the most practical and common software development models used today.
This model is good for medium-scale projects and regulatory sectors, where readability and flexibility are equal priorities. The approach's built-in feedback loops guarantee an excellent output that meets user needs.
CCBP Academy 4.0 can allow one to learn methods like the Iterative Waterfall Model to master their skill sets and compete at a different level in software engineering. It teaches students modern ways of doing things, making professionals efficient and more knowledgeable. The next steps await at CCBP Academy 4.0 as it gives people the door to further possibilities in the tech world.
The Iterative Waterfall Model uses well-defined projects. It requires adjustments that may seem minor, where structured phases, with feedback loops, are in place to support quality and incorporate controlled changes throughout development.
With feedback loops, teams could revisit earlier stages for error correction and design refinement in this model, ensuring the end product of such software would withstand strict quality checks and deployment.
The Iterative Waterfall Model is more structured, follows sequential phases, and contains controlled iterations of the work. Agile emphasises continuous collaboration, incremental delivery, and adaptability to frequent changes in requirements, offering much flexibility.
The model offers an early structured process, error detection, improved quality assurance, documented detail, and predictability of timelines and budgets with controlled flexibility.
Through feedback loops, the model can adapt to moderately changing requirements. However, feedback loops might not be perfect for projects characterised by frequently fluctuating or changing requirements, which is why Agile methodologies are most effective.
Source: NxtWave CCBP Blog
Original URL: https://www.ccbp.in/blog/articles/iterative-waterfall-model
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