OBDA Constraints for Effective Query Answering (Extended Version)

TL;DR

This paper introduces OBDA constraints to optimize SPARQL-to-SQL translation, significantly improving query answering efficiency in large industrial databases by reducing redundancies.

Contribution

The paper proposes two novel OBDA constraints and demonstrates their effectiveness in enhancing query performance through extensive real-world experiments.

Findings

Query answering performance improved up to orders of magnitude.

Redundant joins and unions in SQL queries are effectively reduced.

New OBDA constraints enable more efficient query translation.

Abstract

In Ontology Based Data Access (OBDA) users pose SPARQL queries over an ontology that lies on top of relational datasources. These queries are translated on-the-fly into SQL queries by OBDA systems. Standard SPARQL-to-SQL translation techniques in OBDA often produce SQL queries containing redundant joins and unions, even after a number of semantic and structural optimizations. These redundancies are detrimental to the performance of query answering, especially in complex industrial OBDA scenarios with large enterprise databases. To address this issue, we introduce two novel notions of OBDA constraints and show how to exploit them for efficient query answering. We conduct an extensive set of experiments on large datasets using real world data and queries, showing that these techniques strongly improve the performance of query answering up to orders of magnitude.