@startuml UC09_system_sequence
!theme plain
hide footbox
skinparam sequenceMessageAlign center
skinparam responseMessageBelowArrow true
skinparam BoxPadding 10
autonumber

title UC-09 — Build consistent fused obstacle picture\n(system sequence diagram)

participant "Obstacle sensor\nsubsystem" as Obs
box "Roomba RVC control software\n(black box)" #E8F4FF
  participant "System" as Sys
end box

alt [typical]
  Obs -> Sys : ObstacleStateChanged(rawUpdates)
  note over Sys : feeds UC-02 .. UC-05
else [A1 asynchronous updates]
  Obs -> Sys : ObstacleStateChanged(frontUpdate)
  Obs -> Sys : ObstacleStateChanged(sideUpdate)
  note over Obs, Sys : snapshot alignment TBD
else [E1 fusion incoherent]
  Obs -> Sys : ObstacleStateChanged(rawUpdates)
  note over Obs, Sys : next: UC-08
end

@enduml
