On the sequence of authorization policy transformations

In [2, 3], we proposed a model-based approach to specify the transformation of authorizations based on the principle of minimal change [1] and its application in database systems. Nevertheless, there were some limitations in this approach. Firstly, we could not represent a sequence of transformations. Secondly, default authorizations could not be expressed. In this paper, we propose two high-level formal languages, L^s and L^sd, to specify a sequence of authorization transformations and default authorizations. Our work starts with L^s, a simple, but expressive, language to specify certain sequence of authorization transformations. Furthermore, L^sd has more powerful expressiveness than L^s in the sense that constraints, causal and inherited authorizations, and general default authorizations can be specified.