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Efficient Handling of SPARQL OPTIONAL for OBDA

Xiao, Guohui, Kontchakov, Roman, Cogrel, Benjamin, Calvanese, Diego, Botoeva, Elena (2018) Efficient Handling of SPARQL OPTIONAL for OBDA. In: The Semantic Web - ISWC 2018 - 17th International Semantic Web Conference, Monterey, CA, USA, October 8-12, 2018, Proceedings, Part I. Lecture Notes in Computer Science , 11136. pp. 354-373. Springer ISBN 978-3-030-00670-9. E-ISBN 978-3-030-00671-6. (doi:10.1007/978-3-030-00671-6_21) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided) (KAR id:91264)

The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided. (Contact us about this Publication)
Official URL
https://doi.org/10.1007/978-3-030-00671-6_21

Abstract

OPTIONAL is a key feature in SPARQL for dealing with missing information. While this operator is used extensively, it is also known for its complexity, which can make efficient evaluation of queries with OPTIONAL challenging. We tackle this problem in the Ontology-Based Data Access (OBDA) setting, where the data is stored in a SQL relational database and exposed as a virtual RDF graph by means of an R2RML mapping. We start with a succinct translation of a SPARQL fragment into SQL. It fully respects bag semantics and three-valued logic and relies on the extensive use of the LEFT JOIN operator and COALESCE function. We then propose optimisation techniques for reducing the size and improving the structure of generated SQL queries. Our optimisations capture interactions between JOIN, LEFT JOIN, COALESCE and integrity constraints such as attribute nullability, uniqueness and foreign key constraints. Finally, we empirically verify effectiveness of our techniques on the BSBM OBDA benchmark.

Item Type: Conference or workshop item (Paper)
DOI/Identification number: 10.1007/978-3-030-00671-6_21
Subjects: Q Science > QA Mathematics (inc Computing science) > QA 76 Software, computer programming,
Divisions: Divisions > Division of Computing, Engineering and Mathematical Sciences > School of Computing
Depositing User: Amy Boaler
Date Deposited: 02 Nov 2021 12:38 UTC
Last Modified: 03 Nov 2021 11:22 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/91264 (The current URI for this page, for reference purposes)
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