Authors:
Gopalakrishnan Krishnasamy-Sivaprakasam
1
and
Giora Slutzki
2
Affiliations:
1
Math & Computer Science Department, Central State University, Wilberforce, Ohio, U.S.A.
;
2
Department of Computer Science, Iowa State University, Ames, Iowa, U.S.A.
Keyword(s):
Description Logic, Theory of Database Privacy and Security, Knowledge Representation and Reasoning.
Abstract:
In this paper we study Secrecy-Preserving Query Answering under Open World Assumption (OWA) for DL-LiteR Knowledge Bases (KBs) with acyclic TBox. Using a tableau algorithm, we construct A∗, an inferential closure of the given ABox A, which includes both positive as well as negative assertions. We use a notational variant of Kleene 3-valued semantics, which we call OW-semantics as it fits nicely with OWA. This allows us to answer queries, including Boolean Conjunctive Queries (BCQs) with “Yes”, “No” or “Unknown”, as opposed to the just answering “Yes” or “No” as in Ontology Based Data Access (OBDA) framework, thus improving the informativeness of the query-answering procedure. Being able to answer “Unknown” plays a key role in protecting secrecy under OWA. One of the main contributions of this paper is a study of answering BCQs without compromising secrecy. Using the idea of secrecy envelopes, previously introduced by one of the authors, we give a precise characterization of when BCQs
should be answered “Yes”, “No” or “Unknown”. We prove the correctness of the secrecy-preserving query-answering algorithm.
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