1. An access permissions management system comprising: a hierarchical access permissions repository including a multiplicity of access permissions relating to a multiplicity of data elements which are arranged in a data element hierarchy and wherein: some of said multiplicity of data elements have associated therewith only access permissions which are inherited from data elements ancestral thereto; some of said multiplicity of data elements are prevented from having associated therewith inherited access permissions and thus have associated therewith only unique access permissions which are not inherited; and some of said multiplicity of data elements are not prevented from having associated therewith inherited access permissions and have associated therewith not only inherited access permissions but also unique access permissions which are not inherited, some of which unique access permissions possibly being redundant with inherited access permissions; and an access permissions redundancy prevention engine operative to ascertain which of said unique access permissions are redundant with inherited access permissions and responsively thereto not to store said unique access permissions which are redundant with inherited access permissions in said repository.