|Stable release||2.3.0 / October 21, 2015|
|License||Dual-licensed: GPLv3 and AGPLv3 / commercial|
Neo4j is an open-source graph database implemented in Java and accessible from software written in other languages using the Cypher query language through a transactional HTTP endpoint. The developers describe Neo4j as an ACID-compliant transactional database with native graph storage and processing. Neo4j is the most popular graph database.
Neo4j version 1.0 was released in February, 2010. The community edition of the database is licensed under the free GNU General Public License (GPL) v3. The additional modules, such as online backup and high availability, are licensed under the free Affero General Public License (AGPL) v3. The database, with the additional modules, is also available under a commercial license, in a dual license model.
Neo4j version 2.0 was released in December, 2013.
Licensing and editions
Neo4j comes in 3 editions: Community, Enterprise, and Government. It is dual-licensed: GPLv3 and AGPLv3 / commercial. The Community Edition is free but is limited to running on 1 node only due to the lack of clustering and is without hot backups. The Enterprise Edition (which requires buying a license unless the application built on top of it is open-sourced) unlocks these limitations allowing for clustering, hot backups and monitoring. The Government Edition extends the Enterprise Edition adding additional government specific services including FISMA related certification and accreditation support.
In Neo4j, everything is stored in form of either an edge, a node or an attribute. Each node and edge can have any number of attributes. Both the nodes and edges can be labelled. Labels can be used to narrow searches. As of version 2.0, indexing was added to Cypher with the introduction of schemas. Previously, indexes were supported separately from Cypher.
The Neo Technology board of directors consists of Rod Johnson (founder of the Spring Framework), Chris Barchak (Partner at Conor Venture Partners), Magnus Christerson (Vice President of Intentional Software Corp), Nikolaj Nyholm (Partner at Sunstone Capital), Guarav Tuli (Principal at Fidelity Growth Partners) and Johan Svensson (CTO of Neo Technology).
- Apache Giraph
- Structured storage
- Gremlin (programming language)
- Cypher Query Language
- Graph Database
- Todd Hoff (June 13, 2009). "Neo4j - a Graph Database that Kicks Buttox". High Scalability. Possibility Outpost. Retrieved February 17, 2010.
- Gavin Terrill (June 5, 2008). "Neo4j - an Embedded, Network Database". InfoQ. C4Media Inc. Retrieved February 17, 2010.
- http://neo4j.com/docs/stable/rest-api-transactional.html. Retrieved November 4, 2015. Missing or empty
- Neo Technology. "Neo4j Graph Database". Retrieved November 4, 2015.
- "DB-Engines Ranking of Graph DBMS". DB-Engines. July 2015. Retrieved July 3, 2015.
- "The top 10 ways to get to know Neo4j". Neo4j Blog. February 16, 2010. Retrieved February 17, 2010.
- Emil Eifrem (April 13, 2011). "Graph Databases, Licensing and MySQL". Retrieved April 29, 2011.
- "Neo4j 2.0 GA - Graphs for Everyone". Neo4j Blog. December 11, 2013. Retrieved January 10, 2014.
- "The Neo4j Editions".
- "The Neo4j Manual v2.1.5".
- "The Neo4j Manual v1.8.3".
- Neo Technology. "Staff - Neo4Jj Graph Database". Retrieved February 18, 2015.
- Neo4J in action Neo4j in Action released in Paperback – 21 Dec 2014
-  Neo4j Editions on official website
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