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Below is a concise example of how you might define functional requirements, non-functional requirements, and a class diagram for a simple web‐based purchasing system (as hinted by the “View Items,” “Make Purchase,” and “Client Register” use cases shown in your image).---1.
Functional Requirements1. User Registration (Client Register)The system shall allow a new user to create an account by providing essential information (e.g., name, email, password).The system shall verify that the email address is unique.2. User Login and Session
ManagementThe system shall allow a registered user to log in with valid credentials.The system shall maintain a user session, so the user does not need to log in repeatedly during one session.3. View ItemsThe system shall allow any user (registered or not) to browse products
(e.g., by category, search, etc.).The system shall display product details (name, description, price, availability).4. Shopping CartThe system shall allow a registered user to add items to a virtual shopping cart.The system shall allow the user to remove items or change quantities in
the cart.5. Make PurchaseThe system shall allow a registered user to proceed to checkout and purchase items in the cart.The system shall request shipping and payment details and confirm the order.The system shall generate a purchase confirmation (e.g., order summary, email
confirmation).6. Order ManagementThe system shall store each completed order and its status (e.g., ‘Pending,’ ‘Shipped,’ ‘Delivered’).The system shall allow the user to view order history and track shipment status.---2. Non‐Functional Requirements1. PerformanceThe system
should support at least 1,000 concurrent users without significant performance degradation.Average page load times should be under 2 seconds for broadband users.2. SecurityAll user credentials must be stored securely (hashed passwords, encrypted connections via
HTTPS).Only authenticated users can access personal or order information.3. Availability & ReliabilityThe system should be available 24/7 with an uptime of 99.9%.Critical operations (e.g., completing a purchase) must be reliable, ensuring no data loss on transaction.4.
ScalabilityThe system should be designed to easily handle increased numbers of products and users over time.5. MaintainabilityThe codebase should follow clear naming conventions, modular design, and be well documented to ease maintenance.6. Compliance and PrivacyThe
system must comply with relevant data‐protection regulations (e.g., GDPR).User data (e.g., addresses, payment info) must be protected and only used for authorized purposes.---3. Class Diagram (Example)Below is a simplified UML diagram in text form. (Relationship notations are
approximate for illustration.)+-------------------+ 1..* +-------------------+| Customer |----------------| Order |+-------------------+ +-------------------+| - customerId | | - orderId || - name | | - orderDate || - email | |-
orderStatus || - password | | - totalAmount || + register() | | + placeOrder() || + login() | | + cancelOrder() |+-------------------+ +-------------------+ |1 1..* | has | consists of v
v+-------------------+ 1..* +-------------------+| ShoppingCart |----------------| CartItem |+-------------------+ +-------------------+| - cartId | | - quantity || + addItem() | | - subtotal() || + removeItem() | | - itemId (link) ||
+ getTotal() | | |+-------------------+ +-------------------+ ^ | | +---------------------------+ | Item | +---------------------------+
| - itemId | | - name | | - description | | - price | | - stockQuantity | | + getDetails() | +---------------------------+Explanation of
Key RelationshipsCustomer can have one active ShoppingCart at a time.A ShoppingCart is composed of multiple CartItems.A CartItem references a single Item (product) and stores a quantity.A Customer can place many Orders, and each Order can contain multiple items (as part
of the checkout process).You would expand this diagram to include classes for Payment, Shipping, etc. depending on the complexity of your system. You might also integrate a Category or Catalog class for browsing items, or a Payment class that handles different payment
methods (credit card, PayPal, etc.).---SummaryFunctional requirements focus on what the system must do (user actions like registration, viewing items, making purchases).Non-functional requirements focus on qualities/constraints of the system (performance, security, availability,

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etc.).A class diagram shows how data and behavior might be structured in an object-oriented design for the system.These details should serve as a solid starting point for designing a web‐based purchasing application similar to what you described.