Topic Button 	

    The Topic Button is located in the Search Window.  When
    activated, the Topic Button conducts an Expansion process on the
    data currently in the Search Window Text Entry Area of the
    Search Window.  This Expansion process automatically produces a
    list of terms that have a statistical relationship (also known
    as a heuristic thesaurus) to the data currently in the Search
    Window Text Entry Area.  Normally, the list of terms produced by
    this Expansion process is comprised principally of topically
    related terms.

    The degree of effectiveness of the underlying Expansionalgorithm
    is significantly dependent on the size of the database and the
    degree of focus of the data used for the Expansion process.  The
    larger the database, the more effective the Expansion process. 
    The more specific the terms used as input for the Expansion
    process, the more relevant the resulting list of Expanded Words.

    After the Expansion process has produced a list of Expanded
    terms generically representative of the source data, this list
    of Expanded Words is used by the Topic feature as search terms
    for a Topic Search, the results of which are ranked according to
    the Probable Relevance Ranking algorithm.  (See Search Window in
    this Help system)