The Unified Policy Framework (UPF)

We present the Unified Policy Framework (UPF), a generic framework for modelling security (access-control) policies; in Isabelle/HOL. UPF emphasizes the view that a policy is a policy decision function that grants or denies access to resources, permissions, etc. In other words, instead of modelling the relations of permitted or prohibited requests directly, we model the concrete function that implements the policy decision point in a system, seen as an “aspect” of “wrapper” around the business logic of a system. In more detail, UPF is based on the following four principles: 1. Functional representation of policies, 2. No conflicts are possible, 3. Three-valued decision type (allow, deny, undefined), 4. Output type not containing the decision only.