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.
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A wellbore is a three-dimensional representation of a hole in the ground.
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i.e., individuals in the class .
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Materializing the SQL in the mappings is not an option, since the schema is fixed.
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A property which is functional when restricting its domain/range to individuals generated from a single template.
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Acknowledgement
This work is partially supported by the EU under IP project Optique (Scalable End-user Access to Big Data), grant agreement n. FP7-318338.
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Hovland, D., Lanti, D., Rezk, M., Xiao, G. (2016). OBDA Constraints for Effective Query Answering. In: Alferes, J., Bertossi, L., Governatori, G., Fodor, P., Roman, D. (eds) Rule Technologies. Research, Tools, and Applications. RuleML 2016. Lecture Notes in Computer Science(), vol 9718. Springer, Cham. https://doi.org/10.1007/978-3-319-42019-6_18
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