We study Controlled Query Evaluation (CQE), a declarative approach to confidentiality-preserving data access, in the context of Description Logic (DL) ontologies, particularly for confidentiality policies expressed through Epistemic Dependencies (EDs).
We first address the problem of answering queries (specifically, Boolean unions of conjunctive queries) under known semantics for CQE (GA- and IGA-entailment). Our results show that if the TBox is expressed in $\text{DL-Lite}_{\mathcal{R}}$, CQE is computationally intractable in general.
Moreover, in the presence of EDs, the IGA semantics has recently been proven not to satisfy an important confidentiality preservation property known as indistinguishability. To define computationally easier and confidentiality-preserving forms of CQE, we introduce a new semantics for CQE based on the notion of minimal policy violation (MPV).
We show that the new semantics provides a sound approximation of the previous ones while satisfying the indistinguishability property. We also prove that, in the case of $\text{DL-Lite}_{\mathcal{R}}$ ontologies, query entailment under the MPV semantics can be decided in polynomial time in data complexity.
Finally, we present a software implementation of our framework that we used to evaluate the feasibility of this new approach using an existing benchmark for OWL 2 QL.
Blogger's Review: This research provides a new theoretical foundation for confidentiality-preserving data access in Description Logic ontologies, achieving significant breakthroughs in complexity, demonstrating the effectiveness of MPV semantics. Such work will advance the intersection of data privacy protection and knowledge representation, making it worthy of attention.