, just for a start.
    So we have a picture like this:

                         x              y
                         o-------------&gt;o
                                       /|\
                                      / | \
                                     /  |  \
                                    /   |   \
                                   o    o    o
                                  y_1  y_2  y_3

JA: Let me now draw what I consider to be a critical distinction with respect
    to the quest