PlantUML:Communication Diagram
https://plantuml-proxy.vercel.app/svg/https://scrapbox.io/api/code/suto3/PlantUML:Communication_Diagram/communication.uml#.svg
code:communication.uml
@startuml
rectangle “A Student” as S
rectangle “Online Book Ordering System” as OBOS
rectangle “Fulfillment Center” as FC
rectangle “Books” as B
rectangle “Book Order” as BO
S -right->> OBOS: 1: login
OBOS -down- B
OBOS -down->> FC: 2: submit books\n3: calculate price
FC -- B
FC -down- BO: 4: get quantity
B -right- BO
@enduml