Datomic implementation

<dependency>
   <groupId>com.tinkerpop.blueprints</groupId>
   <artifactId>blueprints-datomic-graph</artifactId>
   <version>??</version>
</dependency>

Graph graph = new DatomicGraph("datomic:mem://tinkerpop");

Datomic Graph Introduction
Datomic is a distributed database system designed to enable scalable, flexible, and intelligent applications, running on next-generation cloud architectures. Datomic stores facts (i.e. your data points) as datoms. A datom represents the addition (or retraction) of a relation between an entity, an attribute, a value, and a transaction. The RDF and SPARQL feel of the Datomic data model and query approach makes it a good target for the implementation of a property graph. For a summary of the Datomic database, please review the following presentations.

The blueprints-datomic-graph implementation supports the property graph data model defined by Blueprints. However, there are a few peculiarities:

1. No user defined element identifiers: Datomic is the gatekeeper and creator of vertex and edge identifiers. Thus, when creating a new vertex or edge instance, the provided object identifier is ignored.
2. DatomicGraph implements IndexableGraph. However, the use of indices is limited when working with Datomic and is explained as follows:
   1. There is no support to create indices.
   2. By default, there is an AutomaticIndex for both vertices and edges. These indexes contain a key for each existing property.

Temporal Graph Database
The DatomicGraph implementation natively supports the notion of time by allowing queries to be performed against a version of the graph in the past. Users can shift time, by employing the setCheckPoint-method, which takes a java.lang.Date as input. Once set, the graph reflects the vertices, edges, and their corresponding properties at the specified time point.

DatomicGraph graph = new DatomicGraph("datomic:mem://tinkerpop");
graph.setCheckPoint(someDate); // Set the graph state at some specific (time-)point in the past
... // Do stuff
graph.setCheckPoint(new Date()); // Restore the graph state (current state)

DatomicGraph Setup
The Datomic Peer library is (currently) not redistributable through Maven. Make sure to download the latest Datomic build through the Datomic website and install the datomic-xxx.jar manually into Maven.

mvn install:install-file -DgroupId=com.datomic -DartifactId=datomic -Dfile=datomic-xxx.jar -DpomFile=pom.xml

Datomic provides several Storage Service options (in memory, DynamoDB, Infinispan, and SQL-database). Consult the information on the Datomic website to choose and set up the appropriate Storage Service.