Temporal Conjunctive Query Answering in the Extended DL-Lite Family

Abstract

Ontology-based query answering (OBQA) augments classical query answering in databases by domain knowledge encoded in an ontology. Systems for OBQA use the ontological knowledge to infer new information that is not explicitly given in the data. Moreover, they usually employ the open-world assumption, which means that knowledge that is not stated explicitly in the data and that is not inferred is not assumed to be true or false. Classical OBQA however considers only a snapshot of the data, which means that information about the temporal evolution of the data is not used for reasoning and hence lost.We investigate temporal conjunctive queries (TCQs) that allow to access temporal data through classical ontologies. In particular, we study combined and data complexity of TCQ entailment for ontologies written in description logics from the extended DL-Lite family. Many of these logics allow for efficient reasoning in the atemporal setting and are successfully applied in practice. We show comprehensive complexity results for temporal reasoning with these logics.

Finding New Diamonds: Temporal Minimal-World Query Answering over Sparse ABoxes

“…Negation in queries with the classical open-world semantics results in non-tractable (mostly coNP or even undecidable) query evaluation (Rosati 2007a;Gutiérrez-Basulto et al 2015). Moreover, prior work (Borgwardt and Thost 2015a;Borgwardt and Thost 2020) on temporalized ontology-mediated query answering with negation shows that the high complexity of temporal query answering with negation is mostly due to the openworld assumption for negation in a query language. There are several approaches how to introduce negation in ontology-mediated query answering without losing tractability, e.g.…”