SPARQL

See Database

• See w:List of SPARQL implementations for all w:triplestores that provide SPARQL querying endpoint
• See w:List of subject-predicate-object databases for purpose built triplestores.

Copyleft or free-of-charge implementations of SPARQL endpoint ability producing software alternatives

• w:Virtuoso Universal Server - http://virtuoso.openlinksw.com/download/ - GPL and proprietary

Tools

• http://d2rq.org/ - Enables writing queries in SPARQL that actually access traditional relational database and receiving results and RDF graphs. Could be very useful as glue code between MediaWiki's data in the MariaDB and the public and private SPARQL databases