问Nhibernate -继承-对子对象的零对一关系，如何映射？(Fluent API)

EN

//Classes
public class Order
{
    public virtual int OrderId { get; set; }
    public virtual string Name { get; set; }
    public virtual ActionCompleted ACO { get; set; }
    public virtual ActionCancelled ACA { get; set; }

}

public class Action
{
    public virtual int ID { get; set; }
    public virtual DateTime ActionDT { get; set; }
    public virtual Order Order { get; set; }
}

public class ActionCompleted : Action
{

}
public class ActionCancelled : Action
{
    public Physician CancelledBy { get; set; }
}

// FluentNHibernate Mappings
public class OrderMap : ClassMap<Order>
{
    public OrderMap()
    {
        Id(x => x.OrderId);

        Map(x => x.Name);
        References(x => x.ACO, "ActionCompletedId");
        References(x => x.ACA, "ActionCanceledId");
    }
}

public class ActionMap : ClassMap<Action>
{
    public ActionMap()
    {
        Id(x => x.ActionID);
        DiscriminateSubclassOn("ActionType");   // if present TPH, otherwise TPC

        Map(x => x.ActionDT);
        References(x => x.Order, "DiagOrderId");
    }
}

public class ActionCompletedMap : SubclassMap<ActionCompleted>
{
    public ActionCompletedMap()
    {
        DiscrimitatorValue("Completed");
    }
}
public class ActionCancelledMap : SubclassMap<>
{
    public ActionCompletedMap()
    {
        DiscrimitatorValue("Completed");
        Refernces(x => x.CancelledBy, "CancelledByPhysician");
    }
}

// factory aka ObjectContext
ISessionFactory factory = Fluently.Configure()
    .DataBase(SqlServerConfiguration.Standard.Connectionstring(connstring))
    .Mappings(m => m.FluentMappings.AddFromAssemblyOf<OrderMap>())
    .BuildSessionFactory();

// FluentNHibernate Mappings
public class OrderMap : ClassMap<Order>
{
    public OrderMap()
    {
        Id(x => x.OrderId);

        Map(x => x.Name);

        Join("ActionTable", join => 
        {
            .KeyColumn("OrderId");
            join.Optional();
            join.Where("ActionType = 'ActionCompleted'");
            join.Component(x => x.ACO, c => 
            {
                c.Map(x => x.ActionID).Not.Insert();
                c.Map(x => x.ActionDT);
                c.ParentReference(x => x.Order);
            }
        }));
        Join("ActionTable", join =>
        {
            join.KeyColumn("OrderId");
            join.Optional();
            join.Where("ActionType = 'ActionCanceled'");
            join.Component(x => x.ACA, c => 
            {
                c.Map(x => x.ActionID).Not.Insert();
                c.Map(x => x.ActionDT);
                c.ParentReference(x => x.Order);
                c.Map(x => x.CanceledBy);
            }
        }));
    }
}