@startuml
skinparam monochrome true
skinparam packageStyle rectangle
skinparam shadowing false

title System Sequence Diagram (SSD)

autonumber

actor "Organization\nEmployee" as Employee
participant ":System" as System

activate Employee

    Employee -> System : asks to add a new entry to the agenda
    activate System

        System --> Employee: to do list
    deactivate System


    Employee -> System : select a entry from the to-do-list, \nand asks the status and the expected duration
    activate System

        System --> Employee : displays operation success
    deactivate System

@enduml