A form of access control that uses an authorization policy that is flexible in the types of evaluated parameters (e.g., identity, role, clearance, operational need, risk, heuristics).
A strategy for managing user access to one or more systems, where the business roles of users is combined with policies to determine what access privileges users of each role should have. Theoretical privileges are compared to actual privileges, and differences are automatically applied. For example, a role may be defined for a manager. Specific types of accounts on the single sign-on server, Web server, and database management system may be attached to this role. Appropriate users are then attached to this role.
NIST SP 800-95 under Policy Based Access Control (PBAC)
(Meta Access Management System Federated Identity and Access Mgmt Glossary)