Handling an order Order placed → In stock?; In stock? → Order from supplier (no); Order from supplier → In stock? (delivered); In stock? → Take payment (yes); Take payment → Orders database; Orders database → Shipped Order placed → In stock? In stock? → Order from supplier (no) Order from supplier → In stock? (delivered) In stock? → Take payment (yes) Take payment → Orders database Orders database → Shipped no delivered yes Order placed In stock? Order from supplier Take payment Orders database Shipped