///<summary>
///adds a subgoal to the front of the subgoal list
///</summary>
///<param name="goal"></param>
public override void AddSubgoal(Goal goal)
{
Subgoals.Push(goal);
}
///<summary>
///a Goal is atomic and cannot aggregate subgoals yet we must implement
///this method to provide the uniform interface required for the goal
///hierarchy.
///</summary>
///<param name="goal"></param>
///<exception cref="ApplicationException"></exception>
public virtual void AddSubgoal(Goal goal)
{
throw new ApplicationException("Cannot add goals to atomic goals");
}
