simple engine flowchart

simple-flow.dot

digraph g {
    rankdir=LR;
    
    io [label="I/O"];

    subgraph cluster_20 {
        label=journal;
        open [label="open\nexisting\njournal"];
        notify [label="start\nprocess"];
        create [label="create\nnew\njournal"];
        update [label="update\njournal and\ncheckpoint"];
        done;
    }

    label=app;
    gen [label="generate\nstatement"];
    exec [label="test and execute\nusing tests from\nold journal"];
    publish [label="publish\nnew\njournal"];

    io -> open [label="journal.Open(journal.From)"];
    open -> io [label="oldJournal, err"];
    io -> notify [label="oldJournal.Process(journal.Input)"];
    notify -> gen [label="App.Generate(journal.Input, oldJournal, oldCheckpoint)"];
    gen -> create [label="statement, err"];
    create -> exec [label="App.Exec(oldJournal, newJournal)"];
    exec -> update [label="newCheckpoint, err"];
    update -> publish [label="App.Publish(newJournal, newCheckpoint)"];
    publish -> done [label="err"];
    done -> io [label="journal.Output, err"];

}