A role hierarchy is automatically generated by hierarchically ranking roles in a role based control system, each role including a plurality of identities having attributes. Iteratively at each hierarchical level: each non-cohesive role (wherein, in this case, at least one attribute is not possessed by every identity in the role) is replaced, at the same hierarchical level, by a cohesive role formed by grouping identities having at least one common attribute. The remaining identities are clustered into children roles based on attributes other than the common attribute, and the children roles are added to the role hierarchy at a hierarchical level below the cohesive role. If no common attribute exists in the non-cohesive role, the role is clustered into two or more new roles based on all the attributes in the role, and the non-cohesive role is replaced with the new roles at the same hierarchical level.