digraph arch {
        md [label="document source\n(Markdown)"];
        md [shape=box];

        bindings [label="bindings file\n(YAML)"];
        bindings [shape=box];

        impl [label="step implementations\n(Python, Rust, ...)"]
        impl [shape=box];

        fable [label="Fable"];
        fable [shape=ellipse];

        pdf [label="PDF document"]
        pdf [shape=box];

        testprog [label="Test program\n(generated)"]
        testprog [shape=box];
        
        report [label="Test report)"]
        report [shape=box];

        md -> fable;
        bindings -> fable;
        impl -> fable;
        fable -> pdf;
        fable -> testprog;
        testprog -> report;
}