Understanding the Waterfall Model: A Complete Requirements Analysis Guide
🎥 Watch before reading: Learn the Requirements Phase of the Waterfall Model in 10 mins!
What Is the Waterfall Model? Origins & Core Phases
The Waterfall Model is one of the earliest and most traditional software development life cycle (SDLC) methodologies. It follows a linear and sequential approach where each phase flows into the next—just like a waterfall.
The Core Phases of the Waterfall Model:
- Requirements Analysis
- System Design
- Implementation
- Testing
- Deployment
- Maintenance
This model is best suited for projects with fixed requirements, minimal expected change, and strong documentation needs.
Deep-Dive: Requirements Phase (Goals, Deliverables, RTM)
The Requirements Analysis phase is the most crucial part of the Waterfall Model. This is where you define what the software should do, gather client expectations, and document every requirement before design begins.
Primary Goals:
- Capture all functional and non-functional requirements.
- Align the development team with business objectives.
- Create documentation that traces requirements to delivery.
Key Deliverables:
- Software Requirements Specification (SRS)
- Requirements Traceability Matrix (RTM)
- Use case diagrams, process flows, or user stories
Step-by-Step Requirements Gathering Checklist ✅
- Interview stakeholders to identify needs
- Develop use cases or user personas
- Review and validate with business teams
- Define clear acceptance criteria
- Create and map the RTM
- Get formal approval/sign-off
Following a repeatable checklist minimizes ambiguity and reduces costly changes during development.
Common Mistakes & How to Avoid Scope Rework
Common Pitfalls:
- Missing edge cases or exceptions
- Skipping stakeholder involvement
- Writing vague or untestable requirements
Solutions:
- Write formal SRS documents
- Hold regular walkthroughs with all teams
- Use RTMs to ensure coverage and testability
Waterfall vs. Agile Requirements—When to Choose Which
| Criteria | Waterfall | Agile |
|---|---|---|
| Requirement Stability | High | Low / Evolving |
| Documentation | Extensive upfront | Minimal, iterative |
| Feedback Loops | Late stage | Frequent |
| Use Case | Government, Healthcare, Finance | Startups, SaaS, Mobile Apps |
Choose Waterfall if your project has clear, fixed goals. Choose Agile if fast iteration and adaptability are priorities.
Real-World Example: Building a Requirements Traceability Matrix
Here’s a simplified example of an RTM used in a banking app project:
| ID | Requirement | Design Ref | Test Cases |
|---|---|---|---|
| R1 | Login with OTP | UI-D1 | TC01, TC02 |
| R2 | View Account Statement | UI-D2 | TC03, TC04 |
An RTM ensures every requirement is mapped to its respective design and test elements—reducing scope creep.
FAQs
Is the Waterfall Model still relevant in 2025?
Yes. It’s still widely used in industries like healthcare, aerospace, and government where documentation and compliance are essential.
How is requirements analysis different in Agile?
Agile requirements evolve in sprints. In Waterfall, everything is detailed and signed off before development begins.
What tools are used for documenting requirements?
Popular tools include Microsoft Word, Lucidchart, Jira, and Confluence. For RTMs, Excel and TraceCloud are commonly used.
Conclusion
Mastering the Requirements Analysis phase is key to successful Waterfall-based software development. By documenting and validating requirements early, teams can avoid costly mistakes and build high-quality software with confidence.
📥 Download Free Resources
- ✅ Requirements Gathering Checklist (PDF)
- 📊 Sample Requirements Traceability Matrix (Excel)
- 📚 Waterfall vs Agile: Full Comparison Guide
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