On the complexity of bounded-variable queries (extended abstract)
PODS '95 Proceedings of the fourteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
The complexity of relational query languages (Extended Abstract)
STOC '82 Proceedings of the fourteenth annual ACM symposium on Theory of computing
Tractable Reasoning and Efficient Query Answering in Description Logics: The DL-Lite Family
Journal of Automated Reasoning
The Complexity of Conjunctive Query Answering in Expressive Description Logics
IJCAR '08 Proceedings of the 4th international joint conference on Automated Reasoning
Scalable Grounded Conjunctive Query Evaluation over Large and Expressive Knowledge Bases
ISWC '08 Proceedings of the 7th International Conference on The Semantic Web
A general datalog-based framework for tractable query answering over ontologies
Proceedings of the twenty-eighth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
DL-Lite: tractable description logics for ontologies
AAAI'05 Proceedings of the 20th national conference on Artificial intelligence - Volume 2
AAAI'05 Proceedings of the 20th national conference on Artificial intelligence - Volume 4
Extending decidable cases for rules with existential variables
IJCAI'09 Proceedings of the 21st international jont conference on Artifical intelligence
Conjunctive query answering in the description logic EL using a relational database system
IJCAI'09 Proceedings of the 21st international jont conference on Artifical intelligence
The DL-lite family and relations
Journal of Artificial Intelligence Research
Journal on data semantics X
Query answering under non-guarded rules in datalog+/-
RR'10 Proceedings of the Fourth international conference on Web reasoning and rule systems
Ontological queries: Rewriting and optimization
ICDE '11 Proceedings of the 2011 IEEE 27th International Conference on Data Engineering
The combined approach to ontology-based data access
IJCAI'11 Proceedings of the Twenty-Second international joint conference on Artificial Intelligence - Volume Volume Three
A sound and complete backward chaining algorithm for existential rules
RR'12 Proceedings of the 6th international conference on Web Reasoning and Rule Systems
Ontology based query answering with existential rules
IJCAI'13 Proceedings of the Twenty-Third international joint conference on Artificial Intelligence
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Ontology-based data access (OBDA) is widely accepted as an important ingredient of the new generation of information systems. In the OBDA paradigm, potentially incomplete relational data is enriched by means of ontologies, representing intensional knowledge of the application domain. We consider the problem of conjunctive query answering in OBDA. Certain ontology languages have been identified as FO-rewritable (e.g., DL-Lite and sticky-join sets of TGDs), which means that the ontology can be incorporated into the user's query, thus reducing OBDA to standard relational query evaluation. However, all known query rewriting techniques produce queries that are exponentially large in the size of the user's query, which can be a serious issue for standard relational database engines. In this paper, we present a polynomial query rewriting for conjunctive queries under unary inclusion dependencies. On the other hand, we show that binary inclusion dependencies do not admit polynomial query rewriting algorithms.