1. A computer-readable storage medium having data structures stored thereon or a computer-readable propagated signal having data structures, the data structures comprising: an access control group data structure to store access control group data; a user access data structure to store user access data wherein the user access data relates to at least one entry in the access control group data structure; and a data object access data structure to store data object access data wherein the data object access data relates to at least one entry in the access control group data structure.