SPARQL 1.0 became an official W3C Recommendation on 15 January 2008. On 26 March 2013, the SPARQL Working Group has produced a new W3C Recommendation SPARQL 1.1 that introduces more features to 2008 version. SPARQL is emerging as the de facto RDF query language. Prior to SPARQL, there were some other popular RDF query languages, such as RQL, SeRQL, TRIPLE, RDQL, and so on. The comprehensive...