A plurality of digital licenses correspond to a piece of content, including a base license and at least one add-on license. Each add-on license includes a reference to the base license, and each of the base license and each add-on license sets forth rules specifying how the content may be employed. Each add-on license is identified by way of the reference therein to the base license, and the rules in the base license and in each identified add-on license are aggregated into an aggregated set of rules that is evaluated to determine if such aggregated set of rules allows employing the content in a particular manner.