1. A computer-implemented method comprising: storing, in a policy store that is stored within a computer-readable storage memory and utilized by a plurality of applications in an enterprise, a first authorization policy that specifies features that are used within a first type of authorization environment; storing, in the policy store, a second authorization policy that specifies features that are used within a second type of authorization environment that differs from the first type of authorization environment; determining that the first authorization policy and the second authorization policy in the policy store are relevant to a request from an application of the plurality of applications; performing a union of the first authorization policy, configured for use within the first type of authorization environment, and the second authorization policy, configured for use within the second type of authorization environment, wherein the second type of authorization environment is an Oracle Access Manager (OAM) environment, in response to the determining, wherein the first authorization policy specifies features of a role-based access control (RBAC) model including a role category to which multiple roles belong, and wherein the second authorization policy specifies features of a discretionary access control (DAC) model; evaluating the union of the first policy and the second policy within a policy engine that evaluates both features that are used within the first type of authorization environment and features that are used within the second type of authorization environment wherein evaluating the features that are used within the first type of authorization policy comprises determining whether an access-requesting subject is associated with a particular role that belongs to the role category; and granting access to at least one resource within the enterprise based on a result of the evaluating.