digraph shared_data {
    rankdir="LR" ;

    subgraph cluster1 {
        style=invisible ;
        node [shape=record];
	xs   [label=" xs ",shape="plain"] ;
	box1 [label="{1| . }"] ;
	box2 [label="{2| . }"] ;
	box3 [label="{3|null}"] ;
        xs   -> box1 ;
	box1 -> box2 ;
	box2 -> box3 ;
    } ;
    subgraph cluster2 {
        style=invisible ;
        node [shape=record];
	ys   [label=" ys ", shape="plain"];
	box0 [label="{0| . }"] ;
        ys   -> box0 ;
	box0 -> box1 ;
    } ;
    subgraph cluster3 {
        style=invisible ;
	zs   [label=" zs ", shape="plain"] ;
	zs   -> box2 ;
    } ;
}