@startuml
participant REST
participant ACM_Runtime
participant Participants
database ACM_Database

REST -> ACM_Runtime: Lock Automation Composition Instance
ACM_Runtime -> ACM_Database: Read Automation Composition Instance Information

alt Automation Composition Instance exists
 alt Automation Composition Instance administrative state is UNLOCKED
  ACM_Runtime -> Participants: [ASYNC] Lock AC Element Instances for this AC Instance
  ACM_Runtime -> ACM_Database: Mark AC Instance and its AC Element Instances as Locking
  ACM_Runtime -> REST: Locking of Automation Composition Instance has been requested
 else
  ACM_Runtime -> REST: Automation Composition instance is not unlocked
 end
else
  ACM_Runtime -> REST: Automation Composition instance does not exist
end

@enduml