digraph class_model {
     rankdir=BT ;
     object  [label="object",  shape=box] ;
     type    [label="type",    shape=box] ;
     P       [label="P", shape=box] ; 
     int     [label="int", shape=box] ; 
     object  -> type   [arrowhead="vee", style="dashed"] ;
     type    -> type   [arrowhead="vee", style="dashed"] ;
     type    -> object [arrowhead="empty"] ;
     P       -> object [arrowhead="empty"] ;
     P       -> type   [arrowhead="vee", style="dashed"] ;
     int     -> object [arrowhead="empty"] ;
     int     -> type   [arrowhead="vee", style="dashed"] ;
}