3. Functional Requirements
Functional requirements define the specific, core behaviors, tasks, and actions a system must perform to meet user needs. They outline what the software must do, including data processing, user interactions, and system responses to inputs. These requirements act as a bridge between user needs and technical design.
Key Aspects of Functional Requirements
- System Functionality: Detailed descriptions of what the software must do, often organized by features, modules, or use cases.
- User Interactions: Explicit steps defining how a user interacts with the system.
- Data Handling: Definitions of inputs, outputs, processes, and data formats.
- Input/Output Handling: How the system reacts to specific inputs or conditions.
- Examples: User registration, data processing, search functionalities, report generation, or security authentication.
Functional requirements are distinguished from non-functional requirements (which describe how a system performs, such as security, usability, or speed).
3.1 Requirement Prioritization
We use the MoSCoW method for prioritization:
- Must Have: Critical for the current delivery cycle.
- Should Have: Important but not vital.
- Could Have: Desirable but can be deferred.
3.2 System Features
3.3 Detailed Functional Logic
For complex requirements, use Steps to define the workflow:
FR-101: Authentication Workflow
Input
User provides email and password via the login form.
Validation
The system validates the email format and checks the password against the encrypted hash in the database.
Response
If successful, the system generates a JWT and redirects to the Dashboard.
3.4 Acceptance Criteria
| Req ID | Acceptance Criteria |
|---|---|
| FR-101 | User is redirected within 2s of clicking “Login” with valid credentials. |
| FR-201 | Suspended users receive a 403 Forbidden error upon subsequent login attempts. |