--- /dev/null
+@startuml
+
+ Rest -> "ACM Runtime": ACM operation triggered by the user
+ activate "ACM Runtime"
+ "ACM Runtime" -> "ACM Database": Read Automation Composition information
+ activate Participant
+ "ACM Runtime" -> Participant : [ASYNC] Send the state change event to the participant
+ "ACM Runtime" -> "ACM Database": Mark the AC element into transitioning state
+ deactivate "ACM Runtime"
+ Participant -> Participant: state change operation get stuck
+ deactivate Participant
+
+ activate "ACM Runtime"
+ "ACM Runtime" -> "ACM Database": Mark TIMEOUT reached for the AC instance
+ deactivate "ACM Runtime"
+
+@enduml