Software development with the Waterfall methodology
The Waterfall Model is a sequential and structured approach to software development. Each phase must be completed before the next begins, ensuring thorough documentation and step-by-step execution. This methodology is beneficial for large-scale projects with stable requirements.
Key phases in the Waterfall approach to software development
The Waterfall model consists of six main phases. Each phase has specific deliverables and generates key documentation for future reference.

1

2

3

4

5

6

1
Requirements Analysis
Gather and define all functional and non-functional requirements
2
System Design
Translate requirements into software architecture
3
Implementation
Code the software based on design specs
4
Testing
Verify system meets all requirements
5
Deployment
Release to production environment
6
Maintenance
Ensure ongoing functionality and updates
1 Requirements analysis
Software engineers work closely with clients and stakeholders at this stage to gather, document, and define all functional and non-functional requirements.
KEY ACTIVITIES
  • Conduct stakeholder meetings and interviews.
  • Define the scope of the project.
  • Identify system constraints (performance, security, usability).
  • Analyse risks and feasibility.
DOCUMENTATION
Software requirements specification (SRS):
  • A detailed document outlining the functional and non-functional requirements.
  • Acts as a contract between stakeholders and developers.
  • Includes user requirements, system capabilities, assumptions, and constraints.
Use case diagrams and user stories:
  • Illustrate how different users will interact with the system.
Risk analysis report:
  • Identifies potential risks and mitigation strategies
2 System design
In this phase, developers translate requirements into a structured software architecture.
KEY ACTIVITIES
  • Design the overall system structure.
  • Identify software components and their interactions.
  • Define data models and database structures.
DOCUMENTATION
High-level design (HLD) document
  • Describes system architecture, major modules, and their interactions.
Low-level design (LLD) document
  • Specifies how each module will function at a detailed level.
  • Includes algorithms, data structures, and class diagrams.
Data flow diagrams (DFD) and entity-relationship (ER) diagrams
  • Illustrate how data moves through the system.
Technology Stack Report
  • Lists programming languages, frameworks, and tools to be used.
3 Implementation (programming)
The actual coding of the software begins based on the design specifications.
KEY ACTIVITIES
  • Develop the software using the selected programming language.
  • Break down the project into modules and functions.
  • Perform unit testing on individual components.
DOCUMENTATION
Source code documentation
  • Well-commented code to help future developers understand the logic.
Module-level design documentation
  • Details individual module structures, inputs, and expected outputs.
Version control logs (GitHub/GitLab repositories, commit history)
  • Tracks development changes and improvements.
Code review reports
  • Documents findings from peer reviews and suggested improvements.
4 Testing
This phase ensures that the entire system meets functional and non-functional requirements.
KEY ACTIVITIES
  • Conduct integration testing (modules working together).
  • Perform system testing to verify that the software meets requirements.
  • Implement User Acceptance Testing (UAT) with real users.
DOCUMENTATION
Test plan document
  • Describes the scope, approach, and criteria for successful testing.
Test case reports
  • Lists individual test cases with expected vs. actual outcomes.
Defect logs and bug reports
  • Records bugs, their severity, and how they were resolved.
Performance test reports
  • Evaluate system response time, load handling, and stress testing.
5 Deployment
Once testing is complete, the software is released to the production environment.
1
1. Server Deployment
Deploy the software on live servers
  • Release Notes & Deployment Guide document version, features, and known issues
  • Installation & Configuration Guide details system setup and configurations
2
2. User Preparation
Prepare users and documentation
  • User Manuals & Help Documentation provide comprehensive usage instructions
  • Conduct user training sessions
3
3. Monitoring & Safety
Ensure smooth deployment with safety measures
  • Monitor for initial feedback and bugs
  • Maintain Rollback Plan for emergency recovery if needed
6 Maintenance
The final phase ensures long-term software functionality and updates.
KEY ACTIVITIES
  • Monitor system performance.
  • Apply bug fixes and security patches.
  • Enhance the software with new features.
DOCUMENTATION
Issue tracking reports
  • Logs new bugs and performance issues reported by users.
Patch management documentation
  • Records updates and their impact on the system.
Performance logs and system health reports
  • Monitors server uptime, response times, and potential bottlenecks.
Software version history
  • Maintains records of all updates and changes made.
When the Waterfall approach works best (and when it doesn't)
Benefits of the Waterfall model
  • Clear structure and documentation: Each phase produces well-documented artifacts for future reference.
  • Easy to manage and track progress: Milestones and phase completion points are clearly defined.
  • Best for projects with stable requirements: Works well when the full scope is known upfront.
  • Well-suited for compliance-heavy projects: Useful for industries requiring detailed documentation (banking, healthcare, defense).
Limitations of the Waterfall model
  • Inflexible to changes: Revisiting previous phases is difficult and costly.
  • Late testing: Bugs found late in development can lead to expensive fixes.
  • Limited client interaction: Users do not see working software until the very end.
  • High risk for long-term projects: Technology may become outdated before deployment.
Effective scenarios for the Waterfall model
The Waterfall model is most effective in specific scenarios, including:
Projects with well-defined requirements
Examples: Banking software and military systems.
Projects with stable technologies
Examples: embedded systems and hospital management software.
Projects that require extensive documentation
Examples: government contracts and healthcare applications.
Case study: NASA space shuttle missions
The Waterfall methodology was used to develop software for the NASA space shuttle missions.
1
Requirements analysis
Extensive documentation defining every function.
2
System design
Complex architecture mapped out for high reliability.
3
Implementation
Highly structured code developed in modules.
4
Testing
Rigorous simulations and validation before launch.
5
Deployment
Software uploaded to shuttle systems.
6
Maintenance
Updates released over decades to ensure functionality