@startuml

hide empty members

skinparam {
    Style strictuml
    Monochrome true
    LineType ortho
}

entity Customer
entity Staff
entity Supplier
entity Sale_Head
entity Sale_Line
entity Order_Head
entity Order_Line
entity Product
entity Assembly
entity Component

Customer ||--o{ Sale_Head
Sale_Head }o-|| Staff
Staff ||-o{ Order_Head
Sale_Head ||--|{ Sale_Line
Order_Head ||--|{ Order_Line
Order_Head }o--|| Supplier
Sale_Line }o--|| Product
Order_Line }o--|| Component
Supplier ||--o{ Component
Product ||-|{ Assembly
Assembly }|-|| Component

@enduml