creat link base given port port point messag coordin instanc port point messag coordin instanc object instanc sequenc diagram draw messag edg class link support inherit doc tigri gef graph mutabl graph model connect object object overrid object connect object port object port object edg type connect port port edg type edg type comment edg connect port port edg type editor cur editor global cur editor mode manag mode manag cur editor mode manag mode mode mode manag hashtabl mode object action type action connect port port edg type action type 