The data structures FARFALLA creates and manages may be thought of as
trees. Figure 
shows a FARFALLA tree representing
some of the data from a MACRO event. All of the data in the tree is
organized into a number of nodes. The figure shows five nodes - one
``Evnt'' node, two ``Erp '' nodes, one ``Wtrk'' node (a track in the
wire view of MACRO) and one ``Strk'' node (a track in the strip view
of MACRO). Every node in the tree (except the top-most node) has
exactly one parent, and every node has zero, one, or more children.
In the figure, a line extends upward from a child to its parent. The
``Evnt'' node is top-most and has no parent, but it has four
children. The two ``Erp '' and the ``Strk'' nodes have no children,
and have the ``Evnt'' node as their parent. The ``Wtrk'' node also
has ``Evnt'' as its parent, and has two children (not shown).
