Requirements Engineering is a critical phase in the software development lifecycle where the needs and conditions for a new or altered software product are defined, documented, and maintained. It ensures that the final product meets the expectations of stakeholders.
Different Types of Requirements in Software Engineering
In software engineering, understanding the different types of requirements is essential for building successful systems. Requirements define what a system should do, how it should perform, and the constraints under which it must operate. They serve as a foundation for design, development, testing, and project management.
Functional Requirements
Definition: Functional requirements describe what the system should do — the specific behavior, functions, and features.
Examples:
- User login and registration
- Payment processing
- Email notifications
- Data input and output
Purpose:
To ensure the system delivers expected functionality that meets user needs.
Non-Functional Requirements
Definition:Non-functional requirements (NFRs) define how the system performs tasks. These are quality attributes or constraints.
Common Types:
- Performance: Response time, throughput
- Usability: Ease of use, accessibility
- Reliability: System uptime, error recovery
- Security: Data protection, access control
- Scalability: Handling growth in users or data
Purpose:
To ensure the system operates efficiently and meets user satisfaction.
Domain Requirements
Definition:Domain requirements are specific to the application domain. They often include business rules, standards, or industry-specific needs.
Examples:
- Compliance with banking regulations
- Medical record handling in healthcare apps
- Tax calculations in finance systems
Purpose:
To align the system with industry expectations and legal requirements.
Interface Requirements
Definition:These describe how the system interacts with external systems, hardware, or users.
Examples:
- API endpoints and data formats
- Communication with third-party services
- User interface design guidelines
Purpose:
To ensure smooth interaction between components or with external systems.
User Requirements
Definition:User requirements capture what end-users expect from the system, often written in natural language or user stories.
Examples:
- “As a user, I want to track my orders.”
- “As a manager, I want to generate monthly reports.”
Purpose:
To represent the user’s perspective and guide development toward user satisfaction.
System Requirements
Definition:System requirements combine functional and non-functional elements and define the overall system behavior and constraints.
Examples:
- System must support 500 concurrent users
- Should be compatible with Windows, macOS, and Linux
Purpose:
To guide developers and engineers on the complete system specification.
Requirement Engineering as Part of the Software Process
Requirement Engineering (RE) plays a foundational role in the software development process. It is the first major phase in the software lifecycle and directly impacts the success, efficiency, and quality of the final product.
What Is the Software Process?
The software process refers to the structured set of activities required to develop a software system. These activities generally include:
Requirement Engineering
- System Design
- Implementation (Coding)
- Testing and Validation
- Deployment
- Maintenance
Role of Requirement Engineering in the Software Process
- Lays the Foundation
RE defines what the system should do and under what conditions. Without clear requirements, the rest of the process lacks direction. - Guides System Design
Design decisions depend entirely on the requirements. Architects and developers use the requirement documents to plan the system structure. - Drives Development
Functional and non-functional requirements provide developers with a blueprint of what to build. - Informs Testing
Test cases are written based on requirements to ensure the system does what it’s supposed to. - Supports Maintenance
Clear and well-documented requirements help maintain the software when it needs to be updated or modified.
Key Activities in Requirement Engineering
- Requirement Elicitation – Collecting information from stakeholders
- Requirement Analysis – Understanding and refining the data
- Requirement Specification – Writing it all down clearly (usually in an SRS)
- Requirement Validation – Ensuring the requirements are correct and approved
- Requirement Management – Handling changes throughout the lifecycle
Why Requirement Engineering Is Critical
- Prevents costly rework
- Reduces project risk
- Improves user satisfaction
- Enables better planning and estimation
- Enhances team communication
Different stages of Requirement Engineering
Summary of Stages
| Stage | Purpose |
|---|---|
| Elicitation | Collect requirements from stakeholders |
| Analysis | Refine and validate collected data |
| Specification | Document requirements formally |
| Validation | Ensure correctness and completeness |
| Management | Track and manage changes over time |
What is Requirement Validation?
Requirement Validation is the process of checking that the documented requirements accurately reflect the stakeholder needs and are ready to be used for design and development.
Objectives of Requirement Validation
- Ensure the software will meet user expectations.
- Detect errors, ambiguities, conflicts, or missing requirements early.
- Confirm that requirements are feasible within time, budget, and technology constraints.
- Make sure all stakeholders agree on the documented requirements.
Common Problems Detected During Validation
- Ambiguous or unclear requirements
- Missing functionality
- Conflicting requirements between different stakeholders
- Unrealistic performance or technical expectations
- Lack of user or business context
Importance of Requirement Validation
- Reduces the cost of errors later in development.
- Builds trust and understanding between clients and development teams.
- Improves the quality of the final product.
- Ensures a smooth transition from requirement phase to design and development.
Requirement Management in Software Engineering
Requirement Management is the process of handling, tracking, and controlling changes to requirements throughout the software development lifecycle. It ensures that the project always aligns with the stakeholders’ evolving needs, even when new demands or challenges appear.
Without proper management, projects can face scope creep, miscommunication, and costly rework.
Why is Requirement Management Important?
- Avoids scope creep (uncontrolled changes that delay projects)
- Saves time and money by reducing rework
- Improves quality by ensuring that final software matches user needs
- Facilitates project tracking and auditing
- Enhances stakeholder satisfaction by managing expectations clearly
Best Practices for Effective Requirement Management
- Use dedicated tools (like Jira, IBM DOORS, Helix RM, Trello) for better tracking.
- Define a clear change control process early in the project.
- Maintain a Requirement Traceability Matrix (RTM).
- Communicate openly and frequently with stakeholders.
- users and customers during validation of requirement changes.
