<e>
    <?pi1 data1?>
    <?pi2 data2?>
    <!-- comment1 -->
    <!-- comment2 -->
    <?pi3 data3?>
    <!-- comment3 -->
    <?pi4 data4?>
    <e2>
        <!-- comment1 -->
        <!-- comment2 -->
        <?pi3 data3?>
        <!-- comment3 -->
        <?pi4 data4?>
    </e2>
</e>