Holding the mouse over a dot leads to showing of the associated term. Double clicking on a term (dot, or label) gives in the right hand panel the list of associated text segments. Double clicking on a text segment name gives the text segment in the bottom panel. To avoid occlusion, the term labels are moving, and the display area can be zoomed.
Background and further details: F. Murtagh et al., "Ontology from textual structure: theory and applications", preprint, 2006.