E-commerce Platform: Product and Order Management

This class diagram illustrates the core components and relationships within an e-commerce platform’s product and order management systems, focusing on modular design for scalability and efficiency.

Core Classes & Attributes

1. Product
   • Attributes: Product ID (PK), Name, Description, Price, Stock Quantity, Category (e.g., Electronics, Apparel), Brand, Dimensions/Weight.
   • Associations:
     • Many-to-Many with OrderItem: A product can be included in multiple orders, and an order can contain multiple products.
     • One-to-Many with ProductVariant: Manages variations (e.g., size, color) via subclasses like ColorVariant or SizeVariant.
2. Order
   • Attributes: Order ID (PK), Order Date, Total Amount, Shipping Address, Billing Address, Status (Pending/Shipped/Delivered/Cancelled).
   • Associations:
     • One-to-Many with OrderItem: An order consists of multiple line items (e.g., 2 t-shirts and 1 phone case).
     • One-to-One with Payment: Links to payment details (e.g., transaction ID, payment method).
     • One-to-One with Customer: Identifies the buyer (Customer ID as FK).
3. OrderItem
   • Attributes: Order Item ID (PK), Quantity, Subtotal, Product ID (FK), Order ID (FK).
   • Role: Represents individual products within an order, calculating subtotals and managing inventory deductions.
4. Category
   • Attributes: Category ID (PK), Category Name, Parent Category ID (for hierarchical structuring, e.g., "Electronics" → "Smartphones").
   • Associations:
     • One-to-Many with Product: Groups products into categories (e.g., "Smartphones" category contains multiple Product instances).
5. InventoryManager
   • Methods: updateStock(Product, quantity), checkStockAvailability(Product).
   • Role: Manages real-time stock updates, preventing overselling and triggering reorder alerts.
6. PricingStrategy
   • Methods: calculateDiscount(Product, orderTotal), applyTax(Subtotal).
   • Role: Implements dynamic pricing rules (e.g., seasonal discounts, bulk pricing) via strategies like PercentageDiscount or FixedPriceOffer.

Key Relationships

1. Product ↔ Category: Many-to-One
   • A product belongs to one category (e.g., "iPhone 15" → "Smartphones" → "Electronics").
2. Order ↔ OrderItem: Composition
   • An Order is composed of OrderItem instances, meaning items cannot exist without an order.
3. Product ↔ ProductVariant: Inheritance/Composition
   • Variants (e.g., "Red T-Shirt") inherit from Product and add unique attributes (e.g., Color = Red, Size = M).
4. Order ↔ Customer: Dependency
   • Orders depend on Customer data (e.g., shipping address from the Customer class).

Business Logic & Workflow

1. Order Placement:
   • When a customer adds a Product to their cart, an OrderItem is created with the selected ProductVariant (if applicable).
   • InventoryManager checks stock availability via checkStockAvailability(), reducing Stock Quantity using updateStock() upon confirmation.
2. Pricing Calculation:
   • PricingStrategy applies discounts (e.g., "10% off for orders over $100") and calculates tax, updating the Order’s Total Amount.
3. Inventory Replenishment:
   • InventoryManager triggers alerts when Stock Quantity falls below a threshold (e.g., reordering products from suppliers).

Design Principles

• Modularity: Separate classes for Product, Order, and InventoryManager allow independent updates (e.g., adding new product types without altering order logic).
• Scalability: Hierarchical Category and ProductVariant structures support future expansions (e.g., new product lines or variant types).
• Single Responsibility: InventoryManager and PricingStrategy focus on specific tasks, improving maintainability.

This class diagram serves as a blueprint for developing a robust e-commerce system, ensuring seamless integration between product catalog management, order processing, and inventory control while accommodating future business growth.