digraph Simple {
    node [shape=record];
    graph [nodesep=1];

    human [label="human [man a]"];
    world [label="[world  c]"];
    server [label="server [a]"];
    another [label="another [b]"];

    server -> test -> human;
    server -> another;
    another -> world;
    human -> next;
    human -> world;

    {rank=same; human world;}
}