Luigi Logrippo at the Université du Québec en Outaouais presents the importance of multi-level access control methods for access control, data secrecy and data privacy. They suggest that an access control system that intends to provide secrecy and privacy must implement a multi-level access control method. In a system with data that is secret and data that is public that is accessed by people who can know the secrets and those that cannot there is an implicit two level of hierarchy of data and people. This hierarchy lends itself to management by grouping secrets based on the people that can know them. These levels of secrets can be arranged into levels with those accessing the higher or more restricted secrets being able also able to access less secret data. Such is the case for RBAC or ABAC type access control systems.
Using directional graph (digraph) theory, he provides a number of mathematical proofs for the operation of access control and data flow systems. Digraph theory appears to provide a useful tool for understanding access control systems. It provides an interesting discussion on the properties of secrecy.
Logrippo, L. (2017, October). Multi-level access control, directed graphs and partial orders in flow control for data secrecy and privacy. In International Symposium on Foundations and Practice of Security (pp. 111-123). Springer, Cham.