Functional and Non-Functional Requirements in System Design

Functional Requirements

• Describe the functional capabilities of a system
• Define what the system must do to meet user needs
• Examples:
  • The system must allow users to log in with a username and password.
  • The system must calculate the total cost of items in a shopping cart.

Non-functional Requirements

• Describe the quality attributes of a system
• Define how the system should perform its functions
• Examples:
  • The system must respond to user input within 2 seconds.
  • The system must be accessible to users with disabilities.

User Stories

• A narrative description of a feature or requirement from the user's perspective
• Typically written in the following format:
  • As a [user role], I want to [perform some task] so that [I can achieve some goal].
• Examples:
  • As a customer, I want to be able to view my order history so that I can track my purchases.
  • As a manager, I want to be able to generate reports on sales trends so that I can make informed business decisions.

Acceptance Criteria

• A set of conditions that must be met in order for a user story or requirement to be considered complete
• Defines the boundaries and expectations of a feature or requirement
• Examples:
  • The system must display a list of all orders placed by the user.
  • The system must generate a report that includes sales data for the past quarter.

Use Cases

• A description of a system's functional capabilities from the user's perspective
• Defines the interactions between the user and the system
• Typically includes:
  • Actor: The user or system that interacts with the system
  • Goal: The user's goal or objective
  • Preconditions: The conditions that must be met before the use case can begin
  • Triggers: The event that initiates the use case
  • Description: The steps involved in the use case
• Examples:
  • Use Case: Place Order
    • Actor: Customer
    • Goal: To place an order for products
    • Preconditions: The customer has a valid account and is logged in
    • Triggers: The customer clicks the "Place Order" button
    • Description: The system validates the order, processes payment, and updates the customer's order history.

Functional Requirements

• Describe the functional capabilities of a system
• Define what the system must do to meet user needs
• Examples of functional requirements include:
  • Allowing users to log in with a username and password
  • Calculating the total cost of items in a shopping cart

Non-functional Requirements

• Describe the quality attributes of a system
• Define how the system should perform its functions
• Examples of non-functional requirements include:
  • Responding to user input within 2 seconds
  • Being accessible to users with disabilities

User Stories

• A narrative description of a feature or requirement from the user's perspective
• Typically written in the format: "As a [user role], I want to [perform some task] so that [I can achieve some goal]"
• Examples of user stories include:
  • As a customer, I want to view my order history so that I can track my purchases
  • As a manager, I want to generate reports on sales trends so that I can make informed business decisions

Acceptance Criteria

• A set of conditions that must be met in order for a user story or requirement to be considered complete
• Defines the boundaries and expectations of a feature or requirement
• Examples of acceptance criteria include:
  • Displaying a list of all orders placed by the user
  • Generating a report that includes sales data for the past quarter

Use Cases

• A description of a system's functional capabilities from the user's perspective
• Defines the interactions between the user and the system
• Typically includes:
  • Actor: The user or system that interacts with the system
  • Goal: The user's goal or objective
  • Preconditions: The conditions that must be met before the use case can begin
  • Triggers: The event that initiates the use case
  • Description: The steps involved in the use case
• Example of a use case:
  • Use Case: Place Order
    • Actor: Customer
    • Goal: To place an order for products
    • Preconditions: The customer has a valid account and is logged in
    • Triggers: The customer clicks the "Place Order" button
    • Description: The system validates the order, processes payment, and updates the customer's order history