The Data Structure Query window lets you specify a data structures
  query.  A data structure query graphically displays the relationships
  between data and the type of the data.  This window lets you specify
  the following attributes:

      o  Type of-type of a given item

      o  of Type-items that are of a given type

  You must specify a reference point to begin a data structure query.
  As such, you must specify either the Type of or the Of type
  attribute, or both.