Open Source NoSQL Databases in Java

Neo4j is a graph database, a fully transactional database that stores data structured as graphs. It is a mature and robust graph database that provides: * an intuitive graph-oriented model for data representation. Instead of static and rigid tables, rows and columns, you work with a flexible graph network consisting of nodes, relationships and properties. * a disk-based, native storage manager completely optimized for storing graph structures for maximum performance and scalability. * massive scalability. Neo4j can handle graphs of several billion nodes/relationships/properties on a single machine and can be sharded to scale out across multiple machines. * a powerful traversal framework for high-speed traversals in the node space. can be deployed as a full server or a very slim database with a small footprint (~500k jar). * a simple and convenient object-oriented API.