Emacs programmable taxonomical grouping for arbitrary objects

 This Emacs library provides a programmable way to classify arbitrary objects
 into a hierarchical taxonomy. (That's a lot of fancy words to say that this
 lets you put things in nested groups.)
 .
 Helpful features include:
 .
 + Dynamic taxonomies: Objects may be classified into hierarchies
   automatically defined at runtime based on their attributes.
 .
 + Reusable taxonomies: Taxonomy definitions may be stored in variables and
   reused in other taxonomies' descendant groups.