This paper offers a new role engineering approach to Role-Based Access Control (RBAC), referred to as visual role mining. The key idea is to graphically represent user-permission assignments to enable quick analysis and elicitation of meaningful roles. First, we formally define the problem by introducing a metric for the quality of the visualization. Then, we prove that finding the best representation according to the defined metric is a NP-hard problem. In turn, we propose two algorithms: ADVISER and EXTRACT. The former is a heuristic used to best represent the user-permission assignments of a given set of roles. The latter is a fast probabilistic algorithm that, when used in conjunction with ADVISER, allows for a visual elicitation of roles even in absence of predefined roles. Besides being rooted in sound theory, our proposal is supported by extensive simulations run over real data. Results confirm the quality of the proposal and demonstrate its viability in supporting role engineering decisions.

The role-based access control (RBAC) model has proven to be cost effective to reduce the complexity and costs of ac-cess permission management. To maximize the advantages offered by RBAC, the role engineering discipline has been introduced. A viable approach is to explore current applica-tions and systems to find de facto roles embedded in existing user permissions, leading to what is usually referred to as role mining. However, a key problem that has not yet been adequately addressed by existing role mining approaches is how to propose roles that have business meaning. In order to do this, we provide a new formal framework that also enjoys practical relevance. In particular, the proposed framework leverages business information—such as business processes and organization structure—to implement role mining algo-rithms. Our key observation is that a role is likely to be meaningful from a business perspective when it involves ac-tivities within the same business process or organizational units within the same branch. To measure the “spreading” of a role among business processes or organization structure, we resort to centrality indices. Such indices are used in our cost-driven approach during the role mining process. Fi-nally, we illustrate the application of the framework through a few examples.