Graph database

In computing, a graph database is a database that uses graph structures for semantic queries with nodes, edges and properties to represent and store data. A key concept of the system is the graph (or edge or relationship), which directly relates data items in the store. The relationships allow data in the store to be linked together directly, and in most cases retrieved with a single operation. This contrasts with conventional relational databases, where links between data are stored in the data itself, and queries search for this data within the store and use the JOIN concept to collect the related data. Graph databases by design allow simple and rapid retrieval of complex hierarchical structures that are difficult to model in relational systems. Graph databases are similar to 1970s network-model databases in that both represent general graphs, but network-model databases operate at a lower level of abstraction and lack easy traversal over a chain of edges.

The underlying storage mechanism of graph database products varies. Some depend on a relational engine and store the graph data in a table. More common examples generally use a key-value store or document-oriented database for storage, making them inherently NoSQL structures. Such structures generally offer a performance advantage because the graph is stored in a format similar to a database index, minimizing its size and retrieval time. Most graph databases based on non-relational storage engines also add the concept of tags or properties, which are essentially relationships lacking a pointer to another document. This allows data elements to be categorized for easy retrieval en masse. Examples of NoSQL graph databases include OrientDB, Neo4j and ArangoDB.

Retrieving data from a graph database requires new concepts and generally a new query language. As of 2016, no other single graph query language has risen to prominence in the same fashion as SQL did for relational databases, and there are a wide variety of systems - most often tightly tied to a particular product. Some standardization efforts have taken place, leading to systems like Gremlin (which works with a variety of graph engines), and the SPARQL system (which has seen some multi-vendor adoption). In addition to having SQL interfaces, some graph databases are accessed through APIs.

Description

Graph databases employ nodes, properties, and edges.

Graph databases are based on graph theory. Graph databases employ nodes, edges and properties.

• Nodes represent entities such as people, businesses, accounts, or any other item you might want to keep track of. They are roughly the equivalent of the record, relation or row in a relational database, or the document in a document database.
• Edges, also known as graphs or relationships, are the lines that connect nodes to other nodes; they represent the relationship between them. Meaningful patterns emerge when examining the connections and interconnections of nodes, properties, and edges. Edges are the key concept in graph databases, representing an abstraction that is not directly implemented in other systems.
• Properties are pertinent information that relate to nodes. For instance, if Wikipedia were one of the nodes, one might have it tied to properties such as website, reference material, or word that starts with the letter w, depending on which aspects of Wikipedia are pertinent to the particular database.

The relational model gathers data together using information in the data itself. For instance, one might look for all the "users" whose phone number contains the area code "311". This would be accomplished by searching selected datastores, or tables, looking in the selected phone number fields for the string "311". This can be a time consuming process in large tables, so relational databases offer the concept of an index which allows data like this to be stored in a smaller sub-table, containing only the selected data and a unique key (or primary key) of the record it is part of. If the phone numbers are indexed, the same search would take place in the smaller index table, gathering the keys of matching records, and then looking in the main data table for the records with those keys. Generally, the tables are physically stored so that lookups on these keys are rapid.

Relational databases do not inherently contain the idea of fixed relationships between records. Instead, related data is linked to each other by storing one record's unique key in another record's data. For instance, a table containing email addresses for users might hold a data item called userpk, which contains the primary key of the user record it is associated with. In order to link users and their email addresses, the system first looks up the selected user records primary keys, looks for those keys in the userpk column in the email table (or more likely, an index of them), extracts the email data, and then links the user and email records to make composite records containing all the selected data. This operation, known as a join, can be computationally expensive. Depending on the complexity of the query, the number of joins, and the indexing of the various keys, the system may have to search through multiple tables and indexes, gather up lots of information, and then sort it all to match it together.

In contrast, graph databases directly store the relationships between records. Instead of an email address being found by looking up its user's key in the userpk column, the user record has a pointer directly to the email address record. That is, having selected a user, the pointer can be followed directly to the email records, there is no need to search the email table to find the matching records. This can eliminate the costly join operations. For instance, if one searches for all of the email addresses for users in area code "311", the engine would first perform a conventional search to find the users in "311", but then retrieve the email addresses by following the links found in those records. A relational database would first find all the users in "311", extract a list of the pk's, perform another search for any records in the email table with those pk's, and link the matching records together. For these types of common operations, a graph database (in theory at least) is significantly faster.

The true value of the graph approach becomes evident when one performs searches that are more than one level deep. For instance, consider a search for users who have "subscribers" (a table linking users to other users) in the "311" area code. In this case a relational database has to first look for all the users with an area code in "311", then look in the subscribers table for any of those users, and then finally look in the users table to retrieve the matching users. In comparison, a graph database would look for all the users in "311", then follow the back-links through the subscriber relationship to find the subscriber users. This avoids several searches, lookups and the memory involved in holding all of the temporary data from multiple records needed to construct the output. Technically, this sort of lookup is completed in O(log(n)) + O(1) time, that is, roughly relative to the logarithm of the size of the data. In comparison, the relational version would be multiple O(log(n)) lookups plus additional time to join all the data.

The relative advantage of graph retrieval grows with the complexity of the query. For instance, one might want to know "that movie about submarines with the actor who was in that movie with that other actor that played the lead in Gone With the Wind". This first requires the system to find the actors in Gone With the Wind, find all the movies they were in, find all the actors in all of those movies who were not the lead in Gone With the Wind, and then find all of the movies they were in, finally filtering that list to those with descriptions containing "submarine". In a relational database this will require several separate searches through the movies and actors tables, doing another search on submarine movies, finding all the actors in those movies, and the comparing the (large) collected results. In comparison, the graph database would simply walk from Gone With the Wind to Clark Gable, gather the links to the movies he has been in, gather the links out of those movies to other actors, and then follow the links out of those actors back to the list of movies. The resulting list of movies can then be searched for "submarine". All of this can be accomplished using a single search.

Properties add another layer of abstraction to this structure that also improves many common queries. Properties are essentially labels that can be applied to any record, or in some cases, edges as well. For instance, one might label Clark Gable as "actor", which would then allow the system to quickly find all the records that are actors, as opposed to director or camera operator. If labels on edges are allowed, one could also label the relationship between Gone With the Wind and Clark Gable as "lead", and by performing a search on people that are "lead" "actor" in the movie Gone With the Wind, the database would produce Vivien Leigh, Olivia de Havilland and Clark Gable. The equivalent SQL query would have to rely on additional data in the table linking people and movies, adding more complexity to the query syntax. These sorts of labels may improve search performance under certain circumstances, but are generally more useful in providing additional semantic data for end users.

Relational databases are very well suited to flat data layouts, where relationships between data is one or two levels deep. For instance, an accounting database might need to look up all the line items for all the invoices for a given customer, a three-join query. Graph databases are aimed at datasets that contain many more links. They are especially well suited to social networking systems, where the "friends" relationship is essentially unbounded. These properties make graph databases naturally suited to types of searches that are increasingly common in online systems, and in big data environments. For this reason, graph databases are becoming very popular for large online systems like Facebook, Google, Twitter and similar systems with deep links between records.

Properties

Compared with relational databases, graph databases are often faster for associative data sets and map more directly to the structure of object-oriented applications. They can scale more naturally to large data sets as they do not typically require expensive join operations. As they depend less on a rigid schema, they are more suitable to manage ad hoc and changing data with evolving schemas. Conversely, relational databases are typically faster at performing the same operation on large numbers of data elements.

Graph databases are a powerful tool for graph-like queries, for example computing the shortest path between two nodes in the graph. Other graph-like queries can be performed over a graph database in a natural way (for example graph's diameter computations or community detection).

History

In the pre-history of graph databases, in the mid-1960s Navigational databases such as IBM's IMS supported tree-like structures in its hierarchical model, but the strict tree structure could be circumvented with virtual records.

Graph structures could be represented in network model databases from the late 1960s. CODASYL, which had defined COBOL in 1959, defined the Network Database Language in 1969.

Labeled graphs could be represented in graph databases from the mid-1980s, such as the Logical Data Model.

A number of improvements to graph databases appeared in the early 1990s, accelerating in the late 1990s with endeavors to index web pages.

In the late 2000s, commercial ACID graph databases such as Oracle Spatial and Graph and Neo4j became available.

In the 2010s, commercial ACID graph databases that could be scaled horizontally became available. SAP HANA additionally brought in-memory and columnar technologies to graph databases. During this time, graph databases of various types have become particularly popular with social network analysis with the advent of social media companies.

List of graph databases

The following is a list of graph databases:

Name	Version	License	Language	Description
AllegroGraph	5.1 (May 2015)	Proprietary. Clients: Eclipse Public License v1.	C#, C, Common Lisp, Java, Python	An RDF and graph database.
ArangoDB	3.0.5 (August 2016)	Apache 2	C, C++ & JavaScript	A distributed multi-model document store and graph database. Highly scalable supporting ACID and full transaction support. Including a built-in graph explorer.
Blazegraph	1.5.3 (September 2015)	GPLv2, evaluation license, or commercial license.	Java	A RDF/graph database capable of clustered deployment. Blazegraph supports high availability (HA) mode, embedded mode, single server mode. As of version 1.3.1, it supports the Blueprints API and Reification Done Right (RDR). Prior to version 1.5.0; formerly named Bigdata.
Bitsy	1.5.0	AGPL, Enterprise license (unlimited use, annual/perpetual)	Java	A small, embeddable, durable in-memory graph database
BrightstarDB	1.10.1 (May 2015)	MIT License	C#	An embeddable NoSQL database for the .NET Framework with code-first data model generation.
Cayley	0.5.0 (March 2016)	Apache 2	Go	An open-source graph inspired by the graph database behind Freebase and Google's Knowledge Graph.
DEX/Sparksee	5.2.0 (2015)	Evaluation, research or development use is free; commercial use is not free	C++	A high-performance and scalable graph database management system from Sparsity Technologies. Its main characteristics is its query performance for the retrieval & exploration of large networks. Sparksee offers bindings for Java, C++, C#, Python and Objective-C. Sparksee 5 mobile is the first graph database for mobile devices.
Dgraph	0.3	Apache 2	Go	Dgraph is a scalable, distributed, low latency, high throughput graph database. Dgraph is available under a very liberal Apache License 2.0.
Filament		BSD	Java	A graph persistence framework and associated toolkits based on a navigational query style.
GraphBase	1.0.03a	Proprietary	Java	A customizable, distributed, small-footprint graph store with a rich tool set from FactNexus.
graphd		Proprietary		The proprietary back-end of Freebase.
Graph Engine	1.0	Office Store Standard Application License (Free)	C++, C#	A distributed, in-memory, large graph processing engine.
Grapholytic	0.1	Proprietary		A distributed GraphDB from MIOsoft.
Horton		Proprietary	C#	A graph database from Microsoft Research Extreme Computing Group (XCG) based on the cloud programming infrastructure Orleans.
HyperGraphDB	1.2 (2012)	LGPL	Java	A graph database supporting generalized hypergraphs where edges can point to other edges.
IBM Graph	1.0 (August 2016)	Proprietary	Java	A highly available, and fully managed graph database-as-a-service based on the Apache TinkerPop stack and offered through Bluemix
IBM System G Native Store	v1.0 (July 2014)	Proprietary	C, C++, Java	A high performance graph store using natively implemented graph data structures and primitives for achieving superior efficiency. IBM System G Native Store can handle various simple graphs, property graphs, and RDF graphs, in terms of storage, analytics, and visualization. Native Store is accessible from most programming languages by providing APIs in C++, Java (Tinkerpop/Blueprints), and Python. Its gShell graph command collection and the Native Store REST APIs provide language-free interfaces.
InfiniteGraph	3.0 (January 2013)	Proprietary	Java	A distributed and cloud-enabled commercial product with flexible licensing.
InfoGrid	2.9.5 (2011)	AGPLv3, free for small entities	Java	A graph database with web front end and configurable storage engines (MySQL, PostgreSQL, Files, Hadoop).
jCoreDB Graph				An extensible database engine with a graph database subproject.
k-infinity	4.0 (2015)	Proprietary, free tryout version and demo scenarios		A semantic graph database which is characterised by its graphical user interface and requires no knowledge of any query language. API is open and based on REST and JSON. Thus it can be easily embedded in existing architectures.
MarkLogic	8.0.4 (2015)	Proprietary, free developer version	Java, JavaScript, XQuery	Multi-model NoSQL database that stores documents (JSON and XML) and semantic graph data (RDF triples). MarkLogic also has a built-in search engine and a full-list of enterprise features such as ACID transactions, high availability and disaster recovery, certified security, and scalability and elasticity.
Neo4j	3.0.1 (May 2016)	GPLv3 Community Edition. Commercial & AGPLv3 options for enterprise and advanced editions	Java, .NET, JavaScript, Python	A highly scalable open source graph database that supports ACID, has high-availability clustering for enterprise deployments, and comes with a web-based administration tool that includes full transaction support and visual node-link graph explorer. Neo4j is accessible from most programming languages using its built-in REST web API interface, as well as a proprietary Bolt protocol with official drivers. Neo4j is the most popular graph database in use as of March 2016.
OpenCog		AGPL	C++, Scheme, Python	Includes a satisfiability modulo theories solver and a unified rule engine for performing both crisp (boolean) logic and probabilistic reasoning. Backed onto Postgres.
Ontotext GraphDB	7	GraphDB Free is free. GraphDB Standard and GraphDB Enterprise are commercially licensed.	Java	A graph database engine, based fully on Semantic Web standards from W3C: RDF, RDFS, OWL, SPARQL. GraphDB Free is a database engine for small projects. GraphDB Standard is robust standalone database engine. GraphDB Enterprise is a clustered version which offers horizontal scalability and failover support and other enterprise features.
Orly	(March 2014)	Apache 2	C++	A highly scalable open source graph database; accessible from most programming languages via its built-in REST web API interface.
OpenLink Virtuoso	7.2.4 (April 2016)	GPLv2 for Open Source Edition. Proprietary for Enterprise Edition.	C, C++	A hybrid database server handling RDF and other graph data, RDB/SQL data, XML data, filesystem documents/objects, and free text. May be deployed as a local embedded instance (as used in the NEPOMUK Semantic Desktop), a single-instance network server, or a shared-nothing elastic-cluster multiple-instance networked server.
Oracle Spatial and Graph	11.2 (2012)	Proprietary	Java, PL/SQL	1) RDF Semantic Graph: comprehensive W3C RDF graph management in Oracle Database with native reasoning and triple-level label security. 2) Network Data Model property graph: for physical/logical networks with persistent storage and a Java API for in-memory graph analytics.
Oracle NoSQL Database	2.0.39 (2013)	Proprietary	Java	RDF Graph for Oracle NoSQL Database is a feature of Enterprise Edition providing W3C RDF graph capabilities in NoSQL Database.
OrientDB	2.2.0 (May 2016)	Community Edition is Apache 2, Enterprise Edition is commercial	Java	OrientDB is an open source 2nd Generation Distributed Graph Database with the flexibility of Documents in one product (i.e., it is both a graph database and a document nosql database at the same time.) It has an open source commercial friendly (Apache 2) license. It is a highly scalable graph database with full ACID support. It has a multi-master replication and sharding. Supports schema-less, schema-full and schema-mixed modes. Has a strong security profiling system based on user and roles. Supports a query language that is so similar to SQL which is friendly to those coming from a SQL and relational database background decreasing the learning curve needed. It has HTTP REST + JSON API.
OQGRAPH		GPLv2		A graph computing engine for MySQL, MariaDB and Drizzle.
Profium Sense	6.0	Proprietary	Java	Profium Sense is a contextual content management platform with a built-in triple store. Profium's own reasoning engine supports OWL 2 RL and RDFS and is optimized to manage continuous information streams that require continuous inferencing on-the-fly. Profium architecture is based on an in-memory database with ACID transaction support and supports distributed high-availability deployment.
R2DF				R2DF framework for ranked path queries over weighted RDF graphs.
ROIS		Freeware	Modula-2	A programmable knowledge server that supports inheritance and transitivity. Used in OpenGALEN as a terminology server.
SAP HANA	SPS12 Revision 120	Proprietary	C, C++, Java, JavaScript & SQL like language	In-memory ACID transaction supported property graph
Semblent Lionsgate	v1.0.3 (December 2014)	Proprietary	JavaScript	A scalable, generic distributed database framework coupled with graph search able to efficiently maintain synchronisation persistently between server side and client side databases via a self-building API.
SPARQLCity	v1.0.95 (October 2014)	GPLv3	C, C++ & JavaScript	SPARQLCity produces SPARQLVerse: A standards and Hadoop based analytic graph engine for performing rich business analytics on structured and semi-structured data.
Sqrrl Enterprise	v1.5.1 (August 2014)	Proprietary	Java	Distributed, real-time graph database featuring cell-level security and mass-scalability.
Stardog	v3.1.5 (July 2015)	Proprietary	Java	Fast, scalable, pure Java semantic graph database.
Teradata Aster	v6 (2013)	Proprietary	Java, SQL, Python, C++, R	A high performance, multi-purpose, highly scalable and extensible MPP database incorporating patented engines supporting native SQL, MapReduce and Graph data storage and manipulation. An extensive set of analytical function libraries and data visualization capabilities are also provided.
Titan	1.0 (September 2015)	Apache 2	Java	A distributed, real-time, scalable transactional graph database developed by Aurelius.
TripleBit			C, C++	A centralized RDF store.
VelocityGraph		Open source with proprietary back-end	C#	High performance, scalable & flexible graph database build with VelocityDB object database.
VertexDB		Revised BSD	C	A graph database server that supports automatic garbage collection.
VivaceGraph	3.0 (December 2014)	MIT License	Common Lisp	Pure Common Lisp graph database.
Weaver	0.2 (April 2015)	BSD licenses	C, Python	A fast, scalable, ACID transactional graph database with replication and migration.
WhiteDB	0.7.0 (October 2013)	GPLv3 and a free commercial licence	C	A graph/N-tuples shared memory database library.
OhmDB	1.0.0 (August 2014)	Apache 2	Java	RDBMS + NoSQL Database for Java.

Features

The table below compares the features of the above graph databases.

Name	Graph Model	API	Query Methods	Visualizer	Consistency	Backend	Scalability
AllegroGraph	RDF	Java, Java:Sesame, JavaJena, Python, Ruby, Perl, C#, Clojure, Lisp, Scala, REST	SPARQL 1.1, Prolog, JIG, JavaScript	Gruff - View Graphs, Visual Query Builder for SPARQL and Prolog	ACID	Native Graph Storage	1 Trillion RDF triples
ArangoDB	Property graph	JavaScript, Blueprints, REST	Graph Traversals via JavaScript, Gremlin	Built-in graph explorer	MVCC/ACID	native C/C++	Replication and sharding
Blazegraph	RDF	Java, Sesame, Blueprints, Gremlin, SPARQL, REST	SPARQL, Gremlin	Blazegraph Workbench UI	MVCC/ACID	Native Java	Embedded, Client/Server, High Availability (HA)
Bitsy	Property graph	Blueprints	Gremlin, Pixy		ACID with optimistic concurrency control	Human-readable JSON-encoded text files with checksums and markers for recovery
DEX/Sparksee	Labeled and directed attributed multigraph	Java, C++, .NET, Python	Native Java, C#, Python and C++ APIs, Blueprints, Gremlin	Exporting functionality to visualization formats	Consistency, durability and partial isolation and atomicity	Native graph. light and independent data structures with a small memory footprint for storage	Master-slave replication
Filament
GraphBase Enterprise(1) GraphBase Agility(2)	(1) mixed, (2) Framework-managed Simple Graph	Java	Bounds Language, embedded Java	GraphPad, BoundsPad, Navigator	ACID, graph-based transactions	proprietary native	(1) shared nothing distributed, (2) simple replication, 100+ billion arcs per server
Graph Engine	Property graph	C#, REST	LINQ, TQL, LIKQ		Atomicity	Native graph store and processing engine	Graphs with billions of nodes, Microsoft Azure Platform
Horton	Attributed multigraph		Horton Query Language (Regular Language Expression + SQL)			C#, .Net Framework, asynchronous communication protocols
HyperGraphDB	Object-oriented multi-relational labeled hypergraph	Custom,Java			MVCC/STM
IBM Graph	Property graph	HTTP	Gremlin, HTTP	Built-in Visualizer		Apache Cassandra, Elasticsearch	Scales seamlessly through cloud platform
IBM System G Native Store	Property graph, RDF*	C++, Java, Python	Native Store gShell, Gremlin, SPARQL	Built-in Visualizer	ACID	Native Graph Storage	Both scale-up (using multithreading) and scale-out (using IBM PAMI)
InfiniteGraph	Labeled and directed multi-property graph	Java, Blueprints (read only)	Java (with parallel, distributed queries), Gremlin (read only)	Graph browser for developers. Plugins to allow use of external libraries	ACID; and a parallel, loosely synchronized batch loader	Objectivity/DB on standard filesystems	Distributed & sharded. Objectivity/DB was first DBMS to store a petabyte of objects
InfoGrid	Dynamically typed, object-oriented graph, multigraphs, semantic models
MarkLogic	RDF triple store	JavaScript and XQuery Semantics APIs, support for Sesame and Jena APIs	SPARQL 1.1, JavaScript, XQuery	MarkLogic Query Console, and support for visualization tools (e.g., Keylines) and integrates with other more robust tools (Smartlogic, Cambridge Semantics, PoolParty)	ACID	Native graph and document storage	Hundreds of billions of triples and documents using a distributed architecture
Neo4j	Property graph	Java, Python, JPython, Ruby, JRuby, JavaScript (Node.js), PHP, .NET, Django, Clojure, Spring, Scala, or Bolt+REST (any language)	Cypher (native/preferred), Java Stored Procedures, Native Java APIs (special cases), Traverser API, REST, Blueprints, Gremlin	Data browser included. Supports a variety of 3rd party tools: Gephi, Linkurio.us, Cytoscape, Tom Sawyer, Keylines, etc.	ACID	Native graph storage with native graph processing engine	Horizontal read scaling via master-slave clustering with cache sharding
Ontotext GraphDB	RDF Triplestore	Java: Sesame, Jena REST APIs: SPARQL 1.1 Protocol (end-point), SPARQL 1.1 Graph Store HTTP Protocol, Linked Data Platform, SPARQL results in JSON, JSON-LD and all RDF syntaxes	SPARQL 1.1 (full support), Geo-spatial extension of SPARQL, FTS extensions: Lucene, SOLR, Elasticsearch queries, through GraphDB Connectors	GraphDB Workbench: Explore, SPARQL queries, repository management, cluster management, RelFinder.)	Persistent, synchronous, asynchronous	Native graph storage	Master-slave replication, high-availability clustering
OpenLink Virtuoso	RDF graph: Triple & Quad (named graphs); expandable column store	SPARQL, XMLA, ODBC, JDBC, ADO.NET, OLE DB, Jena, Sesame, Virtuoso PL/SQL, Java, Python, Perl, PHP, HTTP, etc.	SPARQL 1.1; SPARQL web service endpoint; SQL; others	Pivot Viewer (Silverlight or HTML5); OpenLink Data Explorer; SPARQL-compliant tools; Apache Jena-based tools; XML & JSON-based tools; SQL based tools	ACID	Internal column-store or row-store (depending on licensure), hybrid RDF/SQL/RDB engine	Infinite via Commercial Edition's Cluster Module elastic cluster functionality; simple master-slave clustering of single-server instances also an option.
Oracle Spatial and Graph	RDF graph: Triple & Quad (named graphs); Network Data Model property graph	Java; Apache Jena; PL/SQL	SPARQL 1.1; SPARQL web service end point; SQL	SPARQL-compliant tools; Apache Jena-based tools; XML & JSON-based tools; SQL based tools	ACID	Efficient, compressed, partitioned graph storage; Native persisted in-database inferencing; SPARQL 1.1 & SQL integration; triple-level label security; semantic indexing of documents	Parallel load, query, inference; query controls; scales from PC to Oracle Exadata; supports Oracle Real Application Clusters and Oracle Database 8 exabytes
Oracle NoSQL Database	RDF graph: Triple default graph, Triple & Quad named graphs	Java (Apache Jena)	SPARQL 1.1; SPARQL web service end point	SPARQL-compliant tools; Apache Jena-based tools; XML & JSON-based tools	ACID; configurable consistency & durability policies	Key/value store; W3C SPARQL 1.1 & update; in-memory RDFS/OWL inferencing	Parallel load-query; Query controls for: parallel execution, timeout, query optimization hints
OrientDB	Property graph	Java, Python, JPython, Ruby, JRuby, JavaScript (Node.js), PHP, .NET, Clojure, Spring, Scala, or REST (any language)	Own SQL-like Query Language, REST, Blueprints, Gremlin, SparQL (via Blueprints)	Console and Studio Web tool supporting also graph editor	ACID, MVCC	Custom on disc or in memory	Horizontal read and write scaling via multi-master replication + sharding
OQGRAPH	Property graph		SQL		ACID	MySQL, MariaDB
SAP HANA	Property graph	?	Java, JavaScript, SQL like language	Built-in visualizer	ACID, MVCC	Native graph engine based on in-memory columnar store with native algorithms such as neighborhood search, shortest path, strongly connected components and pattern matching	?
Semblent-Lionsgate	Property graph	Python, JavaScript (Node.js), Django, Scala, or REST	Dave (native/preferred), Native Json APIs, REST	Data Browser included, integrates with 3rd party tools.	Fully Consistent and ACID	Native graph storage with native graph processing engine, Apache Cassandra, Apache HBase	Distributed server and client side, billions of nodes
Sqrrl Enterprise	Property graph	Thrift, Blueprint	Own SQL-like query language and Java API	Integrates with 3rd party tools	Fully Consistent and ACID (transactions limited to a single graph node)	Apache Accumulo	Distributed cluster with tens of trillions of edges
Stardog	RDF	Java, Sesame, Jena, SNARL, HTTP/REST, Python, Ruby, Node.js, C#, Clojure, Spring	SPARQL 1.1	Stardog Web, Pelorus	ACID	Native Graph Storage	50 billion RDF triples on $10,000 server
Titan	Property graph	Java, Blueprints, REST, RexPro binary protocol, Python, Clojure (any language)	Gremlin, SPARQL	Integrates with 3rd party tools	ACID or Eventually Consistent	Apache Cassandra, Apache HBase, MapR M7 Tables, Berkeley DB, Persistit, Hazelcast	Distributed cluster (120 billion+ edges) or single server
TripleBit	Labeled direct graph	C, C++	SPARQL		ACID or Eventually Consistent]	Native graph store and processing engine	billion triples
VertexDB		AJAX API	JSON
Weaver	Property graph	C, Python	Node programs		ACID	HyperDex	Automatic replication and migration

Distributed processing

• Angrapa - graph package in Hama, a bulk synchronous parallel (Bulk Synchronous Parallel (BSP)) platform
• Apache Hama - a pure BSP(Bulk Synchronous Parallel) computing framework on top of HDFS (Hadoop Distributed File System) for massive scientific computations such as matrix, graph and network algorithms.
• Blazegraph - A RDF/graph database capable of clustered deployment. Blazegraph supports high availability (HA) mode, embedded mode, single server mode and has available commercial licenses. As of version 1.3.1, it supports the Blueprints API and Reification Done Right (RDR).
• Cyclops - A computing and communication efficient graph processing system with significantly low communication cost.
• Faunus - a Hadoop-based graph computing framework that uses Gremlin as its query language. Faunus provides connectivity to Titan, Rexster-fronted graph databases, and to text/binary graph formats stored in HDFS. Faunus is developed by Aurelius.
• FlockDB - an open source distributed, fault-tolerant graph database based on MySQL and the Gizzard framework for managing Twitter-like graph data (single-hop relationships).
• Giraph - a Graph processing infrastructure that runs on Hadoop (see Pregel).
• GraphBase - Enterprise Edition supports embedding of callable Java Agents within the vertices of a distributed graph.
• Graph Engine - A free distributed, in-memory, large graph processing engine, formerly named Trinity.
• GoldenOrb - Pregel implementation built on top of Apache Hadoop
• GraphLab - A framework for machine learning and data mining in the cloud
• GraphX - GraphLab built on the Spark cluster computing system. Dr. Joseph Gonzalez is the project lead, the creator of GraphLab.
• HipG - a library for high-level parallel processing of large-scale graphs. HipG is implemented in Java and is designed for distributed-memory machine
• IBM System G Graph Analytics Toolkit - A comprehensive graph analytics library consisted of network topological analysis tools, graph matching and search tools, and graph path and flow tools. It has been applied to various use cases and industry solutions.
• Imitator - A reliable distributed graph processing system with replication-based fault-tolerance.
• InfiniteGraph - a commercially available distributed graph database that supports parallel load and parallel queries.
• JPregel - In-memory java based Pregel implementation
• Lionsgate - A distributed, browser-based graph database developed by Semblent.
• KDT - An open-source distributed graph library with a Python front-end and C++/MPI backend.
• Mizan - An optimized Pregel clone that can be deployed easily on Amazon EC2, local clusters, stand-alone Linux systems and supercomputers (IBM BlueGene/P). It utilizes runtime graph repartitioning between iterations to provide dynamic load balancing for better algorithm performance.
• OpenLink Virtuoso - the shared-nothing Cluster Edition supports distributed graph data processing.
• Oracle Spatial and Graph - loading, inferencing, and querying workloads are automatically and transparently distributed across the nodes in an Oracle Real Application Cluster, Oracle Exadata Database Machine, and Oracle Database Appliance.
• Phoebus - Pregel implementation written in Erlang
• Pregel - Google's internal graph processing platform, released details in ACM paper.
• Powergraph - Distributed graph-parallel computing on natural graphs
• PowerLyra - A distributed graph analytics based on GraphLab using differentiated graph computing and partitioning on skewed (e.g., power-law and bipartite) graphs: dynamically applying different computing and partition strategies for different vertices
• PowerSwitch - Adaptive prediction and mode switch (sync & aysnc) on graph-parallel computing
• Sedge - A framework for distributed large graph processing and graph partition management; including an open source version of Google's Pregel
• Signal/Collect - a framework for parallel graph processing written in Scala
• Sqrrl Enterprise - distributed graph processing utilizing Apache Accumulo and featuring cell-level security, massive scalability, and JSON support
• Titan - A distributed, disk-based graph database developed by Aurelius
• Parallel Boost Graph Library (PBGL) - a C++ library for graph processing on distributed machines, part of Boost framework
• Weaver - A fast and scalable graph store designed specifically for dynamically-changing graphs

Shared-memory graph processing

• Ligra - A framework for graph processing using shared-memory multicores written in C++ and using Cilk Plus and OpenMP for parallelism
• Galois - A programming framework that can be used to implement graph algorithms and APIs
• Polymer - A shared-memory graph processing system using the interface of the Ligra system with optimizations for NUMA machines
• X-Stream - An edge-centric graph framework that runs in shared-memory and also includes disk-based optimizations

GPGPU graph processing

• Medusa - A framework for graph processing using graphics processing units (GPUs) on both shared memory and distributed environments; allows users with no GPU programming expertise to leverage GPUs for graph processing

APIs and graph query-programming languages

• Bounds Language – terse C-style syntax which initiates concurrent traversals in GraphBase and supports interaction between them.
• Blueprints – a Java API for Property graphs from TinkerPop and supported by a few graph database vendors.
• Blueprints.NET – a C#/.NET API for generic property graphs.
• Bulbs – a Python persistence framework for TinkerPop, Gremlin Server, Rexster, Titan, and Neo4j Server.
• Cypher Query Language – a declarative graph query language for Neo4j that enables ad hoc and programmatic (SQL-like) access to the graph. Spec opened up as openCypher project.
• Dave – a declarative graph query language for Semblent – Lionsgate
• GraphQL – Facebook query language for any backend service
• Gremlin – an open-source graph programming language that works over various graph database systems.
• Neo4jClient – a .NET client for accessing Neo4j.
• Neography – a thin Ruby wrapper that provides access to Neo4j via REST.
• Neo4jPHP – a PHP library wrapping the Neo4j graph database.
• NodeNeo4j – a Node.js driver for Neo4j that provides access to Neo4j via REST
• Pacer – a Ruby dialect/implementation of the Gremlin graph traversal language.
• Pipes – a lazy dataflow framework written in Java that forms the foundation for various property graph traversal languages.
• Pixy – a declarative graph query language that works on any Blueprints-compatible graph database
• PYBlueprints – a Python API for Property graphs.
• Pygr – a Python API for large-scale analysis of biological sequences and genomes, with alignments represented as graphs.
• Rexster – a graph database server that provides a REST or binary protocol API (RexPro). Supports Titan, Neo4j, OrientDB, Dex, and any TinkerPop/Blueprints-enabled graph.
• RDFSharp – a .NET API for modeling RDF graphs, storing them on many SQL databases (Firebird, MySQL, PostgreSQL, SQL Server, SQLite) and querying them with SPARQL.
• SPARQL – a query language for databases, able to retrieve and manipulate data stored in Resource Description Framework format.
• SPASQL – an extension of the SQL standard, allowing execution of SPARQL queries within SQL statements, typically by treating them as subquery or function clauses. This also allows SPARQL queries to be issued through "traditional" data access APIs (ODBC, JDBC, OLE DB, ADO.NET, etc.)
• Spring Data Neo4j – an extension to Spring Data (part of the Spring Framework), providing direct/native access to Neo4j
• Oracle SQL and PL/SQL APIs – have graph extensions for Oracle Spatial and Graph.
• Styx (formerly named Pipes.Net) – a dataflow framework for C#/.NET for processing generic and property graphs.
• Thunderdome – Titan Rexster object-graph mapper for Python. No longer maintained.
• Mogwai – a Titan Rexster Object-Graph Mapper for Python – Forked from Thunderdome
• Rexpro-Python – Titan Rexpro connection handler for Python.

See also

• Structured storage
• Object database
• Graph transformation for a complementary topic (rule based in memory manipulation of graphs instead of transaction safe Persistence).
• RDF Database

External links

• DB-Engines Ranking of Graph DBMS by popularity, updated monthly