@startuml ../images/05_seq.png
title 
MNStorage.update() Operation
Obsoletes an existing object "A" with new object "B"
end title

actor User
participant MN
participant CN

User -> MN: update(A, B)
activate MN
MN -> MN: update sysmeta for A
deactivate MN
... Next synchronization interval ...
CN -> MN: listObjects(tstart)
activate CN
activate MN
MN -> CN: object list
deactivate MN
CN -> CN: process object list
deactivate CN

== Alternative ==

User -> MN: update(A, B)
activate MN
MN -> CN: setObsoletedBy(A, B)
activate CN
note right
  Alternative mechanism for a 
  V1 MN to update the obsoletedBy 
  property of system metadata
end note
CN -> MN:
deactivate CN
MN -> CN: getSystemMetadata(A)
deactivate MN

== Alternative V2 ==

User -> MN: update(A, B)
activate MN
MN -> MN: update sysmeta for A
MN -> CN: synchronize(A)
MN -> CN: synchronize(B)
deactivate MN
... Potential delay depending on CN sync backlog ...
CN -> MN: getSystemMetadata(A)
CN -> MN: getSystemMetadata(B)

@enduml