Thomas Studer

Provable data privacy

In relational database systems a combination of privileges and views is employed to limit a users access and to hide non-public data. The data privacy problem is to decide whether the views leak information about the underlying database instance. Or, to put it more formally, the question is whether there are certain answers of a database query with respect to the given view instance. In order to answer the problem of provable date privacy, we will make use of query answering techniques for data exchange. We also investigate the impact of database dependencies on the privacy problem. An example about health care statistics in Switzerland shows that we also have to consider dependencies which are inherent in the semantics of the data.

Cut-free common knowledge

Abstract Starting off from the infinitary system for common knowledge over multi-modal epistemic logic presented in [L. Alberucci, G. Jager, About cut elimination for logics of common knowledge, Annals of Pure and Applied Logic 133 (2005) 73–99], we apply the finite model property to “finitize” this deductive system. The result is a cut-free, sound and complete sequent calculus for common knowledge.

A formal model of data privacy

Information systems support data privacy by constraining users access to public views and thereby hiding the non-public underlying data. The privacy problem is to prove that none of the private data can be inferred from the information which is made public. We present a formal definition of the privacy problem which is based on the notion of certain answer. Then we investigate the privacy problem in the contexts of relational databases and ontology based information systems.

Extending the system T0 of explicit mathematics: the limit and Mahlo axioms

Abstract In this paper we discuss extensions of Fefermans theory T 0 for explicit mathematics by the so-called limit and Mahlo axioms and present a novel approach to constructing natural recursion-theoretic models for (fairly strong) systems of explicit mathematics which is based on nonmonotone inductive definitions.

Data Privacy for

Information systems support data privacy by granting access only to certain (public) views. The data privacy problem is to decide whether hidden (private) information may be inferred from the public views and some additional general background knowledge. We study the problem of provable privacy in the context of

\mathcal{ALC}

\mathcal{ALC}

Knowledge Bases

knowledge bases. First we show that the

Universes in explicit mathematics

\mathcal{ALC}

First steps towards probabilistic justification logic

privacy problem wrt. concept retrieval and subsumption queries is ExpTime-complete. Then we provide a sufficient condition for data privacy that can be checked in PTime.

Partial realization in dynamic justification logic

Abstract This paper deals with universes in explicit mathematics. After introducing some basic definitions, the limit axiom and possible ordering principles for universes are discussed. Later, we turn to least universes, strictness and name induction. Special emphasis is put on theories for explicit mathematics with universes which are proof-theoretically equivalent to Fefermans T 0 .