OpenLink Virtuoso is a scalable, high-performance SQL-200n compliant object-relational database engine. It provide sophisticated database management for SQL, XML, and RDF. All interaction with Virtuoso occurs via its support of industry standard query languages, protocols, APIs, and data formats such as: ODBC, JDBC, OLE-DB, ADO.NET, XMLA, SQL, SPARQL, XQuery, SOAP, HTTP, WebDAV, SyncML, Atom (Publishing and Syndication), RSS, RDF, and more.
4store is an efficient, scalable, and stable RDF database. It was developed to underpin Semantic Web applications. It has been providing a base platform for these applications for around 3 years. It has successfully held and run queries over databases of 15GT, supporting a Web application used by hundreds of thousands of people.
The Linked Media Framework is an easy-to-set-up server application that bundles central Semantic Web technologies to offer advanced services. The Linked Media Framework consists of LMF Core and LMF Modules. The core component of the Linked Media Framework is a Linked Data Server that allows you to expose data following the Linked Data Principles. The Linked Data Server implemented as part of the LMF goes beyond the Linked Data principles by extending them with Linked Data Updates and by integrating management of metadata and content and making both accessible in a uniform way. Its extensions are described in more detail in LinkedMediaPrinciples. In addition to the Linked Data Server, the LMF Core also offers a highly configurable Semantic Search service and a SPARQL endpoint. Setting up and using the Semantic Search component is described in SemanticSearch. Accessing the SPARQL endpoint is described in SPARQLEndpoint. Whereas the extension of the Linked Data principles is already conceptually well-described, work is proceeding on a proper specification and extension of Semantic Search and SPARQL endpoint for Linked Data servers.