  In this paper, we propose the use of epistemic dependencies to express data
protection policies in Controlled Query Evaluation (CQE), which is a form of
confidentiality-preserving query answering over ontologies and databases. The
resulting policy language goes significantly beyond those proposed in the
literature on CQE so far, allowing for very rich and practically interesting
forms of data protection rules. We show the expressive abilities of our
framework and study the data complexity of CQE for (unions of) conjunctive
queries when ontologies are specified in the Description Logic DL-Lite_R.
Interestingly, while we show that the problem is in general intractable, we
prove tractability for the case of acyclic epistemic dependencies by providing
a suitable query rewriting algorithm. The latter result paves the way towards
the implementation and practical application of this new approach to CQE.
