Privacy policies and modal logic

If you’ve followed this blog for a while, you may know that I do a lot of work with data privacy and that I have an interest in modal logic. Recently these two worlds collided: I became aware of work that uses modal logic to reason about data privacy. The story begins with Helen Nissenbaum’s paper Privacy as Contextual Integrity [1]. Rather than simply classifying data as public or private, Nissenbaum looks at norms around the context in which data exists and moves. … the benchmark of privacy is contextual integrity; that in any given situation, a complaint that privacy has been violated is sound in the event that one or the other types of the informational norms has been transgressed. A couple years later Nissenbaum coauthored a paper [2] with three Stanford computer scientists using modal logic, specifically linear temporal logic (LTL), to reason about contextual integrity. The paper uses four modal operators: the usual box and diamond, plus past tense versions with a minus sign…