TIUFC ACTION NEXT LEVEL (1894)    PROTOCOL (101)

The user's current position in the Hierarchy is marked by the bolded
entry.  Action permits user to navigate down the Hierarchy by selecting an
item under the highlighted entry.  The selected item becomes the new
current position.
 
Note that Next Level differs from Expand/Collapse.  Although both actions
do expand the selected entry, Next Level also changes the user's current
position in the hierarchy and limits future expansion to items of that
entry.