From the webpage:
Neo4j.rb is a graph database for JRuby.
You can think of Neo4j as a high-performance graph engine with all the features of a mature and robust database. The programmer works with an object-oriented, flexible network structure rather than with strict and static tables — yet enjoys all the benefits of a fully transactional, enterprise-strength database.
It uses two powerful and mature Java libraries:
New features include:
Rules, and