Author(s): Dimitris Bilidas, Manolis Koubarakis
Abstract: Redundant processing is a key problem in SPARQL to SQL query translation in Ontology Based Data Access (OBDA) systems. Many optimizations that aim to minimize this problem have been proposed and implemented. However, a large number of redundant duplicate answers are still generated in many practical settings, and this is a factor that impacts query execution. In this work we identify specific query traits that lead to duplicate introduction and we track down the mappings that are responsible for this behavior. Through experimental evaluation using the OBDA system Ontop, we exhibit the benefits of early duplicate elimination and show how to incorporate this technique into query optimization decisions.
Keywords: query optimization; OBDA; SPARQL