Neo4j is an open source graph database, which is available to Ruby through the Neo4j.rb gem.
Neo4j::Rails::Model object implement most ActiveModel features, making it easy to integrate Neo4j into a Rails application.
Documentation for Neo4j.rb.
rvm use jruby-1.6.7
open browser at localhost:3000
Notice that the neo4j-admin gem is included, which make it possible to visualize the graph database.
Open a browser localhost:7474
Notice that the neo4j-admin gem does not work with JRuby 1.7, see github.com/andreasronge/neo4j-admin/issues/8