OrientDB

Free and Open Source Document Database 2015 ArangoDB is a distributed free and open-source database with a flexible data model for documents, graphs, and key-values. Its query language AQL (ArangoDB Query Language) supports joins, graph queries, list iteration, results filtering, results projection, sorting, grouping, aggregate functions, unions and intersections. Transactions…

Free and Open Source Graph Database 2015 Graph databases are primarily concerned with nodes and the connections between them (usually called edges). They tend to be used for their high performance and their natural ability to model rich data (rich in relationships). Some of these are free and others open…