Sometimes you don‘t know at ‘design time’, if you want to trigger a participant or subprocess.

  Ruote.process_definition do
    sequence do
      participant 'alice'
      ref '${solver}'
      participant 'charlie'
    end
  end

In this process, solver‘s name could be a participant name or a subprocess name.

Subprocesses have the priority over participants.

Note : this expression is used by the worker when substituting unknown expression names with participant or subprocess refs.