classDiagram
    class Customer {
        +name: string
        +email: string
    }
    class Order {
        +id: int
        +date: string
        +total: float
    }
    class OrderItem {
        +quantity: int
        +price: float
    }
    class Product {
        +name: string
        +sku: string
    }
    Customer "1" --> "*" Order
    Order "1" *-- "1..*" OrderItem
    OrderItem "*" --> "1" Product
