@startuml
Participant user as u
Participant client as c
Participant resource as cr
Participant server as s

group responsetime
 u -> c: request
 activate c #Black
' note left of c: user\nwaits\nfor\nresponse
 group waittime
  c -> cr: wait
  activate cr #Yellow
  note right of cr: client\nwaits\nfor\nresource
  cr -> c:
  deactivate cr
 end

 group servicetime
  c ->> s: request
  activate s #Blue
  note right of s: server\nprocesses\nrequest
  s ->> c: response
  deactivate s
 end
 c -> u: response
 deactivate c
end

@enduml