interface IChoice
{
  enum Style {State, Mixed, Event};
  in Style choose();
  out void ss();
  out void sm();
  out void se();
  out void es();
  out void em();
  out void ee();
  out void ms();
  out void mm();
  out void me();

  behaviour
  {
    Style preference = Style.State;

    [preference.State]
    {
      on choose: {preference = Style.State; ss; reply(preference);}
      on choose: {preference = Style.Mixed; sm; reply(preference);}
      on choose: {preference = Style.Event; se; reply(preference);}
    }

    on choose: [preference.Event] {preference = Style.State; es; reply(preference);}
    on choose: [preference.Event] {preference = Style.Mixed; em; reply(preference);}
    on choose: [preference.Event] {preference = Style.Event; ee; reply(preference);}

    [preference.Mixed] on choose: {preference = Style.State; ms; reply(preference);}
    on choose: 
      {
        [preference.Mixed] {preference = Style.Mixed; mm; reply(preference);}
        {[preference.Mixed] {preference = Style.Event; me; reply(preference);}}
      }
  }
}