digraph sysdiag {
    rankdir=LR

    graph [fontname="arial"];
    node [fontname="arial"];
    edge [fontname="arial"];

    subgraph cluster_01 {
        label="Modul zprávy"

        Z_REST_CLIENT [shape=box,label="REST klient"]
        Z_REST_SERVER [shape=box3d,label="REST server"]
        Z_HTTP_SERVER [shape=box3d,label="HTTP server"]
    }

    subgraph cluster_02 {
        label="Modul burza"

        B_REST_CLIENT [shape=box,label="REST klient"]
        B_REST_SERVER [shape=box3d,label="REST server"]
        B_HTTP_SERVER [shape=box3d,label="HTTP server"]
    }

    USER [label="Uživatel"]

    Z_REST_CLIENT -> B_REST_SERVER
    B_REST_CLIENT -> Z_REST_SERVER

    USER -> Z_HTTP_SERVER
    USER -> B_HTTP_SERVER
}