Graph Database in Java (other than Neo4J)

Question

Greetings,
Is there any open source graph database available other than Neo4J??

NOTE: Why not Neo4J?
Neo4J is opensource, but counts primitives (number of nodes,relationships & properties). If you are using it for commercial use. And does not have any straight forward information of pricing on official website. so there can be potential vendor lock-in (Although I have just started my company, and don't have budget to spent money on software anyway.) so It is out of option.

Regards,

Answer 1

OrientDB (old link) appears to support graph storage in much the same was as Neo4j

Answer 2

As RobV said, if your graphs can be represented in just about any custom format such as RDF or DOT language, you're in luck! Here's various options you have:

• RDF: Jena - Considered to be the de facto implementation of RDF for Java, however it has it's oddities such as heavy usage of Iterators.
• RDF: Protégé - If you don't use Jena (and even if you would) but would like to use RDF, Protégé is the tool for you. It's basically a really well done ontology editor which makes handling the graph data a breeze. It also uses a plugin hierarchy similar to Eclipse and there's loads of plugins available so you can plugin stuff like OWL ontologies easily.
• DOT: GraphViz - Another very popular tool, GraphViz can generate graphs from DOT language. Very powerful, a bit tricky to learn but also potentially all you need.

Of course if it fits your company's profile, you could develop your own and start selling it as a product.

Answer 3

Wikipedia lists some other alternatives: http://en.wikipedia.org/wiki/Graph_database