Minimal Disclosure in Hierarchical Hippocratic Databases with Delegation

Hippocratic Databases have been proposed as a mechanism to guarantee the respect of privacy principles in data management. We argue that three major principles are missing from the proposed mechanism: hierarchies of purposes, delegation of tasks and authorizations (i.e. outsourcing), and the minimal disclosure of private information. In this paper, we propose a flexible framework for the negotiation of personal information among customers and (possibly virtual) enterprises based on user preferences when enterprises may adopt different processes to provide the same service. We use a goal-oriented approach to analyze the purposes of a Hippocratic system and derive a purpose and delegation hierarchy. Based on this hierarchy, effective algorithms are given to determine the minimum set of authorizations needed for a service. In this way, the minimal authorization table of a global business process can be automatically constructed from the collection of privacy policy tables associated with the collaborating enterprises. By using effective on-line algorithms, the derivation of such minimal information can also be done on-the-fly by the customer wishing to use the services of a virtual organization.