The Data Structure Query window lets you specify a data structure
  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-The type of a given item.

     o  of Type-The 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.