(1) DFront's create new DFront objects as the first step
    of an update, an inter-front computation.
(2) The second step is the assembly of one DFront object
    into another.
(3) I.e., DFront objects do not have internal access to
    others of their own class during the update.
(4) Later, we can write the code to perform the update 
    with direct-action-on-storage of the two DFront's.