Functional requirements are an important aspect of system design that define the specific features, functions, and behaviors that a system must provide to meet user and business needs. They describe what the system should do and how it should respond to different inputs and situations.
- Specify the services, operations, and tasks the system must perform for users.
- Define how the system reacts to user actions, inputs, and specific conditions.
Example: In an online banking system, users should be able to log in, check account balances, and transfer funds. The system must validate user credentials and process transactions accurately.
Characteristics
Functional requirements describe the specific actions and services a system must provide to users.
- Define system features and functionalities.
- Specify inputs, outputs, and processing behavior.
- Can be tested and verified during development.
- Focus on what the system should do.
Importance of Documenting Functional Requirements
Documenting functional requirements helps ensure that the system's expected features and behaviors are clearly defined and understood by all stakeholders.
- Clarifying Expectations: Helps stakeholders agree on what the system should do and how it should behave.
- Guiding Development: Provides developers with a clear roadmap for designing, building, and testing system functionalities.
- Improving Communication: Serves as a common reference for stakeholders, developers, testers, and project managers.
- Managing Scope: Clearly defines system boundaries, making it easier to evaluate changes and control project scope.
Example
Consider a simple example of Functional Requirements for an online bookstore system
User Functions
The following functional requirements define the actions that users can perform within the online bookstore system.
- Users should be able to register for a new account by providing their name, email address, and password.
- Registered users should be able to log in to the system using their username/email and password.
- Users should be able to browse through the list of available books by category such as genre, author, or popularity.
- Users should be able to view detailed information about a selected book, including its title, author, description, price, availability, and reviews.
- Users should be able to add selected books to their shopping cart for purchase.
- Users should be able to proceed to checkout, enter billing and shipping information, and complete the purchase.
- Users should be able to update their account information, including name, email address, password, and shipping address.
Administrative Functions
The following functional requirements define the actions that administrators can perform to manage the bookstore system.
- Administrators should be able to manage the inventory of books, including adding new books, updating book information, and removing discontinued books.
- Administrators should be able to view and respond to customer inquiries, feedback, and support requests.
- Administrators should be able to manage orders, view order details, and update order statuses as needed.
Functional Requirements vs Non-Functional Requirements
| Functional Requirements | Non-Functional Requirements |
|---|---|
| Define what the system should do. | Define how well the system should perform. |
| Focus on features and functionality. | Focus on performance, security, reliability, etc. |
| Example: User login and registration. | Example: Login response time under 2 seconds. |
| Describe system behavior. | Describe system quality attributes. |
