The Class Browser Query window lets you specify a class browser query.
  A class browser query graphically displays the relationships between
  classes, according to the range you specify.  This window lets you
  specify the following attributes:

     o  Used by-Uses by a class.

     o  Using-Uses of a class.

     o  Depth-The specified number of levels of usage.

  You must specify a reference point to begin a class browser query.  As
  such, you must specify either the Used by or Using attribute, or both.