“In Eifrem’s view, there are only four types of NoSQL databases:
key value stores, BigTable types like Apache Cassandra, document
databases like CouchDB and MongoDB, and the fourth is Graph
databases like Neo4j.
“In the graph data model, there are nodes with type
relationships across nodes,” Eifrem said.
Eifrem said a graph database can then attach key value pairs to
nodes and their relationship. He noted that the way nodes are
connected is a first-class citizen in the graph data model.