The following article discusses visualization possibilities for back-of-book indexes, with headings and subheadings, but since finding aids are in a sense an index to archival material, and since archives in general are increasingly exploring (a) new ways to represent information and (b) linked data, I thought it might be of general interest:
Those three things - autonomy, complexity, and a connection
between effort and reward - are, most people agree, the three
qualities that work has to have if it is to be satisfying.
-- Malcolm Gladwell, "Outliers"