Graph querying engine
In the last decade, due to the large diffusion of non-structured data, NoSQL databases have started to gain considerable attention and importance. Among them, graph databases are indeed extremely powerful for storing information based on a relation between entities. Indeed, in many applications, data can naturally be seen as entities, associated with metadata in the form of node properties, connected by edges that also have properties that further describe the relationship between entities.
Examples of graph databases are libraries or tools such as Neo4j, OrientDB, ArangoDB, Amazon Neptune, Cassandra, JanusGraph (previously named TitanDB), Google Spanner Graph, and Microsoft Cosmos DB. In the following sections, we will briefly describe some of them, together with the languages that allow us to query and traverse the underlying graphs, which are called graph querying languages.
Neo4j
At the time of writing, Neo4j (https://neo4j.com/) is one of the...