user { # User
  n1: circle label:"Start Callback Pattern"
  n2: diamond label:"Receive Callback Pattern event"
  n4: rectangle label:"Execute Callback Pattern action"
  n7: rectangle label:"Monitor Callback Pattern status"
  n10: circle label:"End Callback Pattern"
  n1.handle(right) -> n2.handle(left)
  n2.handle(bottom) -> service.n3.handle(top) [label="Yes/Approved"]
  n4.handle(bottom) -> app.n5.handle(top)
  n7.handle(right) -> app.n8.handle(top)
  n2.handle(top) -> n4.handle(top) [label="No/Rejected"]
}

app { # App
  n5: rectangle label:"Record Callback Pattern outcome"
  n8: rectangle label:"Monitor Callback Pattern status"
  n5.handle(bottom) -> service.n6.handle(top)
  n8.handle(bottom) -> service.n9.handle(top)
}

service { # Service
  n3: rectangle label:"Validate Callback Pattern conditions"
  n6: rectangle label:"Monitor Callback Pattern status"
  n9: rectangle label:"Monitor Callback Pattern status"
  n9.handle(right) -> user.n10.handle(bottom)
  n6.handle(right) -> user.n7.handle(bottom)
  n3.handle(left) -> app.n5.handle(left)
}