digraph G {
    "appli KDE" [shape=box];
    "appli KDE" -> "Phonon";
    "Phonon" -> "PulseAudio" [label="API ALSA"];
    "appli GNOME" [shape=box];
    "appli GNOME" -> "PulseAudio" [label="API PulseAudio ou ESD"];
    "PulseAudio" -> "ALSA";
};