RDF Databases edit 
Our list of and information on commercial, open source and cloud based RDF databases and associated technologies, including MarkLogic, AllegroGraph, Stardog, BlazeGraph and alternatives to these. Databases designed to support the storage of RDF (or triple) data. RDF (Resource Description Framework) is a W3C data model standard that describes data as subject–predicate–object expressions (or triples). This allows the creation of graphs of knowledge, however unlike more general purpose graph databases, there is no support for properties or labels - everything is represented using triples. Data is queried using the SPARQL query language (another W3C standard). Internally, data can be considered to be stored as a single table containing three columns (the subject, predicate and object), with indexing to support the traversal and enumeration of predicates (relationships) for a given subject. A number of triple ontologies (or schemas) are also available that define standard subject/object and predicate types allowing for data interchange, including OWL and RDFS. The W3C standards were introduced to support semantic web and Linked Open Data use cases that focus on semantics and inference. The W3C standards for RDF and SPARQL are available online at https://www.w3.org/RDF/ and http://www.w3.org/TR/rdf-sparql-query/ respectively. The relevant Wikipedia pages are also good places to start at https://en.wikipedia.org/wiki/Resource_Description_Framework and https://en.wikipedia.org/wiki/SPARQL. DB Engines has a list of RDF databases at https://db-engines.com/en/ranking/rdf+store The following analyst material covers a number of technologies in this category:Category Definition
Further Information
RDF Frameworks
Eclipse RDF4J An Eclipse open source project for working with RDF data, including provision of a standard SPARQL interface that can be integrated with backend databases. Previously known as Sesame - http://rdf4j.org/ Jena Framework for developing Semantic Web and Linked Data applications in Java - http://jena.apache.org/ Commons RDF Commons library for working with RDF data - http://commons.apache.org/proper/commons-rdf/ Redland Open source C libraries for working with RDF data - http://librdf.org/ CubicWeb https://www.cubicweb.org/ Commercial RDF Databases
Amazon Neptune Graph and RDF database service with support for TinkerPop Gremlin and RDF SPARQL - https://aws.amazon.com/neptune/ MarkLogic Commercial ACID compliant XML/JSON document store with support for creation of triple indexes over documents queryable via SPARQL - http://www.marklogic.com/ OpenLink Virtuoso Universal Server Supports persistence of documents, relational, RDF and graph data - https://virtuoso.openlinksw.com/ Franz AllegroGraph Commercial ACID compliant that supports both RDF and property graphs, with a free edition available - https://allegrograph.com/allegrograph/ Ontotext GraphDB Commercial RDF database, previously known as OWLIM, and with a free edition available - https://ontotext.com/products/graphdb/ Complexible Stardog RDF database that also support property graphs and data virtualisation, with a community edition available - http://www.stardog.com/ Dydra Cloud based - https://dydra.com/ SparkleDB https://www.syssurge.com/Products/SparkleDB/Home.aspx Cray Graph Engine https://www.cray.com/products/analytics/cray-graph-engine Oracle Spatial and Graph option for Oracle Database Adds RDF (and graph) capabilities to the Oracle database - http://www.oracle.com/technetwork/database/options/spatialandgraph/overview/index.html RDF Graph for Oracle NoSQL Database http://www.oracle.com/technetwork/database/database-technologies/nosqldb/overview/index.html Open Source RDF Databases
BlazeGraph Open Source RDF graph database with property graph features, queryable via SPARQL and Tinkerpop - https://www.blazegraph.com/ 4store https://github.com/4store/4store RedStore https://www.aelius.com/njh/redstore/ Mulgara Open source java RDF database - http://mulgara.org/ BrightstarDB Open Source RDF database for the .NET platform - http://brightstardb.com/ Strabon Spatiotemporal RDF store - http://www.strabon.di.uoa.gr/ Rya (Incubating) RDF triple store built on Apache Accumulo - http://rya.apache.org/ eBay Beam Distributed RDF store - https://github.com/eBay/beam Blog Posts