What are real SPARQL queries like?

  • Authors:

  • Francois Picalausa;Stijn Vansummeren

  • Affiliations:

  • Université Libre de Bruxelles, Belgium;Université Libre de Bruxelles, Belgium

  • Venue:
  • Proceedings of the International Workshop on Semantic Web Information Management
  • Year:
  • 2011

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Abstract

We present statistics on real world SPARQL queries that may be of interest for building SPARQL query processing engines and benchmarks. In particular, we analyze the syntactical structure of queries in a log of about 3 million queries, harvested from the DBPedia SPARQL endpoint. Although a sizable portion of the log is shown to consist of so-called conjunctive SPARQL queries, non-conjunctive queries that use SPARQL's union or optional operators are more than substantial. It is known, however, that query evaluation quickly becomes hard for queries including the non-conjunctive operators union or optional. We therefore drill deeper into the syntactical structure of the queries that are not conjunctive and show that in 50% of the cases, these queries satisfy certain structural restrictions that imply tractable evaluation in theory. We hope that the identification of these restrictions can aid in the future development of practical heuristics for processing non-conjunctive SPARQL queries.