What is the Waterfall Model in SDLC?
The Waterfall Model, the initial Process Model, is commonly known as a linear-sequential life cycle model. It follows a linear and structured approach, where each development phase finishes before the next one begins. Developers and stakeholders find it easy to comprehend and apply. In this model, each step must reach full completion before the team starts the next stage. Project managers primarily use it for large-scale projects with well-defined requirements. After each phase, the team reviews progress to determine whether to continue or halt the project. This structured methodology is why many refer to it as the waterfall lifecycle model.
The typical phases include requirements gathering, design, implementation, testing, deployment, and maintenance. The Waterfall Model emphasizes a fixed and clear set of requirements, allowing little to no flexibility once a phase concludes. Project teams commonly adopt it for projects with stable, well-defined needs. This waterfall development model ensures a smooth transition from one phase to the next, just like water flowing down steps—hence the name.
Phases of Waterfall Model
Following are the major phases of the waterfall model.
Requirements Analysis and Specification Phase
In this phase, the team collaborates closely with the customer to fully understand and document the exact software requirements. Together, they capture all necessary functions, performance expectations, and interfacing needs. This step focuses on defining what the system should do, rather than how it should do it. As a result, the team creates a comprehensive Software Requirement Specification (SRS) document written in plain language to clearly explain system functionality.
Design Phase
During the design phase, the development team translates the requirements gathered in the SRS into a format suitable for programming. They define the overall architecture and produce both high-level and detailed design blueprints. This information is then recorded in a Software Design Document (SDD), which guides the developers during coding.
Implementation and Unit Testing
The team begins coding based on the complete SDD. Developers implement the design using the relevant programming languages. In the waterfall development model, testing also begins at this stage. First, they test small individual modules in isolation. Then, they evaluate interactions between modules and check how the output flows through the system using supporting code.
Integration and System Testing
This phase plays a critical role in determining the final product’s quality. Effective testing leads to satisfied customers, accurate results, and lower maintenance costs. While unit testing focuses on single modules, this stage examines how modules interact with one another and with the overall system.
Operation and Maintenance Phase
Once the software is delivered, installed, and in use, the responsibility for maintenance shifts to the users and support team. Even in the waterfall lifecycle model, this phase remains vital for maintaining usability and performance over time.
When to use Waterfall Model?
Every software development project has unique needs and demands a suitable SDLC approach. Teams should choose the waterfall development model in the following situations:
Requirements are well-documented, clear, and stable.
- The product definition does not change.
- The technology is mature and unlikely to evolve.
- There is no ambiguity in the requirements.
- Skilled resources are available to support each phase.
- The timeline for project completion is relatively short.
Advantages of the Waterfall Model
The waterfall development model offers strong control and clear departmental boundaries. Teams can create structured schedules and track each stage with specific deadlines. The process progresses through concept, design, development, testing, deployment, and finally, maintenance.
Here are several notable advantages of the waterfall model:
- It is simple, clear, and user-friendly.
- Its structure supports easy management with clear deliverables.
- The sequential order of phases ensures a methodical workflow.
- It fits larger projects with well-understood requirements.
- Clearly defined stages and milestones support progress tracking.
- Organizing tasks becomes straightforward.
- Both the process and results are well-documented.
Disadvantages of the Waterfall Model
Despite its structure, the waterfall model offers limited flexibility. Once the project reaches the testing phase, revisiting or changing earlier design choices becomes difficult.
Key disadvantages of the waterfall model include:
- It involves high risk and uncertainty.
- It doesn’t handle changing requirements well.
- Measuring in-progress results within a phase is often difficult.
- Changing scope during development may lead to project failure.
- Integration typically occurs at the end, which delays the discovery of technical or business problems.
This rigidity becomes more apparent when comparing the waterfall model vs agile, as Agile supports frequent revisions and incremental updates throughout development.
Conclusion
In this model, obtaining sign-off for each phase’s deliverables remains essential. While modern methodologies like Agile and Prototype dominate today’s landscape, this model still holds value for large, structured projects. When the requirements are fixed and easy to verify, the waterfall lifecycle model can offer reliable results. Ultimately, a comparison of waterfall model vs agile reveals that although Agile suits dynamic projects, Waterfall works best in well-structured environments with clearly defined goals.
