Controlled Query Evaluation in General Semantics with Incomplete Information

Inauguraldissertation an der Philosophisch-naturwissenschaftlichen Fakult t der Universit t Bern. The thesis describes possible mechanisms that allow manipulations of query-sequences in order to hide secret information from a potentially malicious query-agent. This is investigated in a strictly formal way: The surrounding information framework is reduced to general semantics and allows modelling of incomplete information.