A Proof Procedure for Data Dependencies
Journal of the ACM (JACM)
Journal of the ACM (JACM) - The MIT Press scientific computation series
On conjunctive queries containing inequalities
Journal of the ACM (JACM)
On the decidability of query containment under constraints
PODS '98 Proceedings of the seventeenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Complexity of answering queries using materialized views
PODS '98 Proceedings of the seventeenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Data exchange: semantics and query answering
Theoretical Computer Science - Database theory
Proceedings of the twenty-fifth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Tractable Reasoning and Efficient Query Answering in Description Logics: The DL-Lite Family
Journal of Automated Reasoning
Proceedings of the twenty-seventh ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Laconic schema mappings: computing the core with SQL queries
Proceedings of the VLDB Endowment
Data exchange: On the complexity of answering queries with inequalities
Information Processing Letters
The DL-lite family and relations
Journal of Artificial Intelligence Research
Query Languages for Data Exchange: Beyond Unions of Conjunctive Queries
Theory of Computing Systems
The limits of querying ontologies
ICDT'07 Proceedings of the 11th international conference on Database Theory
On the complexity of query answering over incomplete XML documents
Proceedings of the 15th International Conference on Database Theory
Conjunctive queries with negation over DL-Lite: a closer look
RR'13 Proceedings of the 7th international conference on Web Reasoning and Rule Systems
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One of the most prominent applications of description logic ontologies is their use for accessing data. In this setting, ontologies provide an abstract conceptual layer of the data schema, and queries over the ontology are then used to access the data. In this paper we focus on extensions of conjunctive queries (CQs) and unions of conjunctive queries (UCQs) with restricted forms of negations such as inequality and safe negation. In particular, we consider ontologies based on members of the DL-Lite family. We show that by extending UCQs with any form of negated atoms, the problem of query answering becomes undecidable even when considering ontologies expressed in the core fragment of DL-Lite. On the other hand, we show that answering CQs with inequalities is decidable for ontologies expressed in DL-$Lite^{\mathcal{H}}_{core}$. To this end, we provide an algorithm matching the known coNP lower bound on data complexity. Furthermore, we identify a setting in which conjunctive query answering with inequalities is tractable. We regain tractability by means of syntactic restrictions on the queries, but keeping the expressiveness of the ontology.