public override EventTarget OnAvtive()
        {
            DataFragment fragment = PtApp.ActiveDocument.Database.GetFragment();
            m_Constraint = new UmlTimeLineConstraint(fragment);

            m_SceneNode = new UmlTimeLineGraphicNode(m_Constraint);

            PtApp.ActiveView.TransientObjectObserver.AddNode(m_SceneNode);

            return base.OnAvtive();
        }
 public UmlTimeLineGraphicNode(UmlTimeLineConstraint constraint)
     : base(constraint)
 {
 }