+@code{unindexed} is 01, and @code{index} is -1. Ordinarily a group
+has some nested content, so that @code{n-subcategories} is positive,
+but a few instances of groups with @code{n-subcategories} 0 has been
+observed. If @code{merge} is 00, the most common value, then the
+group is really a distinct group that should be represented as such in
+the visual representation and user interface. If @code{merge} is 01,
+however, the categories in this group should be shown and treated as
+if they were direct children of the group's parent group (or if it has
+no parent group, then direct children of the dimension), and this
+group's name is irrelevant and should not be displayed. (Merged
+groups can be nested!)