Ancestry allows the records of a ActiveRecord model to be organized in a tree structure, using the materialized path pattern. It exposes the standard relations (ancestors, parent, root, children, siblings, descendants) and allows them to be fetched in a single query. Additional features i...

An awesome nested set implementation for Active Record

Easily and efficiently make your ActiveRecord model support hierarchies

A gem that adds simple support for organizing ActiveRecord models into parent–children relationships.

NOTICE: official repository moved to https://github.com/bbommarito/acts_as_nested_set

better_nested_set Rails plugin (my fork from official SVN)

ActiveRecord extension for sorted adjacency lists support

Arboreal is yet another extension to ActiveRecord to support tree-shaped data structures. Internally, Arboreal maintains a computed "ancestry_string" column, which caches the path from the root of a tree to each node, allowing efficient retrieval of both ancestors and descendants. Arboreal surf...

Adds directed acyclic graph functionality to ActiveRecord.