A non-timestamped authorization model for data management systems

There are two approaches to representing authorizations in data management systems. The first approach associates a timestamp with each authorization; semantics of grant and revoke operations on authorizations are based on the temporal relationships determined by these timestamps. The second approach differs from the first in that it does not assign timestamps to authorizations. Although the semantics of the grant and revoke operation are different as a result, several systems have adopted this approach since it not only simplifies management of authorizations, but appears to be more desirable from the user's point of view as well. In this paper, we define a formal model for non-timestamped authorizations that supports both positive and negative authorizations. We give the semantics of the grant and revoke operations in terms of their effect on existing authorizations, and show how negative and positive authorizations can coexist in our model.