A description is provided of a conceptual model for a data secure system. The discussion first offers a formal working vocabulary and next, using the intuitive idea of a dichotomy between permissible and impermissible accesses, formalizes the idea with an Extended Logical Data Base and with protection specifications and patterns. These…

Although the indispensibility of access control mechanisms in data secure systems has been recognized, there is a need for more subtle protection and refined control mechanisms. This report describes context protection mechanisms which enable the same data unit to be protected differently in different contexts, the differences being determined by…