SPARQL-LD: A SPARQL Extension for Fetching and Querying Linked Data

Abstract. SPARQL is a standard query language for retrieving and manipulating RDF data. However, the majority of SPARQL implemen-tations require the data to be available in advance, i.e., to exist in main memory or in a RDF repository (accessible through a SPARQL end-point). Nonetheless, Linked Data exists in the Web in various forms; even an HTML Web page can contain RDF data through RDFa, or RDF data may be dynamically created by a Web Service. In this paper, we propose and demonstrate an extension of SPARQL 1.1, called SPARQL-LD, that allows to directly and exibly exploit this wealth of data. SPARQL-LD al-lows to fetch, query and integrate in the same SPARQL query: i) data coming from online RDF or JSON-LD les, ii) data coming from derefer-enceable URIs, iii) data embedded in Web pages as RDFa, iv) data that is dynamically created by Web Services, and v) data coming by querying other endpoints. A distinctive characteristic of this extension is that it enables to fetch and query even data in datasets returned by a portion of the query, i.e. discovered at query-execution time.