. Under the
  hood, <code>fifo_scheduler&lt;&gt;</code> is just a thin wrapper around an
  object of its <code>FifoWorker</code> template parameter (which manages the
  queue and ensures thread safety) and a
  <code>processor_container&lt;&gt;</code> (which manages the lifetime of the
  state machines).</p>

  <p>The UML standard mandates that an event not triggering a reaction in a
  state machine should be silently discarded. Since a
  <code>fifo_scheduler&lt;&gt;</code> object is itself also a state mach