A policy data structure defines predetermined authorizations, each relating to authorization of at least one user to access at least one resource as well as to dynamic access requests. Each dynamic access request indicates a condition to be satisfied by a respective set of attributes associated with a user request to access a resource and for the request to be granted in absence of an authorization determinative of the request. If the structure does not define an authorization for a request to access a resource, it is determined whether the structure defines a dynamic access requirement determinative for the request, and if so, whether to grant the request in accordance with the respective set of attributes associated with the request. For at least one request, after determining whether to grant the request, a dynamic authorization relating to authorization to access the resource within the request is added to the structure.