From the post:
Lately, I’ve been playing around with the graph database Neo4j and its application to certain classes of problems. Graph databases are meant to solve problems in domains where data relationships can be multiple levels deep. For example, in a relational database, it’s very easy to answer the question “Give me a list of all actors who have been in a movie with Kevin Bacon”:
Using Neo4j with a scripting language, PHP, that is popular with librarians.