Federated RDF Query Processing

Abstract

Synonyms • SPARQL Federation • Federation of SPARQL Endpoints Definitions Federated RDF Query Processing is concerned with querying a federation of RDF data sources where the queries are expressed using a declarative query language (typically, the RDF query language SPARQL) and the data sources are autonomous and heterogeneous. The current literature in this context assumes that the data and the data sources are semantically homogeneous, while heterogeneity occurs at the level of data formats and access protocols. In its initial version, the SPARQL query language did not have features to explicitly express queries over a federation of RDF data sources. To support querying such a federation without requiring the usage of specific language features the following assumption has been made throughout the literature: The result of executing any given SPARQL query over the federation should be the same as if the query was executed over the union of all the RDF data available in all the federation members.