The Bag Semantics of Ontology-Based Data Access
Abstract
Ontology-based data access (OBDA) is a popular approach for integrating and querying multiple data sources by means of a shared ontology. The ontology is linked to the sources using mappings, which assign views over the data to ontology predicates. Motivated by the need for OBDA systems supporting database-style aggregate queries, we propose a bag semantics for OBDA, where duplicate tuples in the views defined by the mappings are retained, as is the case in standard databases. We show that bag semantics makes conjunctive query answering in OBDA CONP-hard in data complexity. To regain tractability, we consider a rather general class of queries and show its rewritability to a generalisation of the relational calculus to bags.
Cite
Text
Nikolaou et al. "The Bag Semantics of Ontology-Based Data Access." International Joint Conference on Artificial Intelligence, 2017. doi:10.24963/IJCAI.2017/170Markdown
[Nikolaou et al. "The Bag Semantics of Ontology-Based Data Access." International Joint Conference on Artificial Intelligence, 2017.](https://mlanthology.org/ijcai/2017/nikolaou2017ijcai-bag/) doi:10.24963/IJCAI.2017/170BibTeX
@inproceedings{nikolaou2017ijcai-bag,
title = {{The Bag Semantics of Ontology-Based Data Access}},
author = {Nikolaou, Charalampos and Kostylev, Egor V. and Konstantinidis, George and Kaminski, Mark and Grau, Bernardo Cuenca and Horrocks, Ian},
booktitle = {International Joint Conference on Artificial Intelligence},
year = {2017},
pages = {1224-1230},
doi = {10.24963/IJCAI.2017/170},
url = {https://mlanthology.org/ijcai/2017/nikolaou2017ijcai-bag/}
}