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.