2.6 Research Issues

The access control matrix is very general. Are there other models, simpler to work with, but equally expressive? Chapter 3, "Foundational Results," explores some of these issues, especially the application of the notion of types to expressive power. Similarly, examining the effects of different types of rules may affect the expressive power of the models.

Database security is an example of a simple application of the access control matrix model. The complexity arises because the elements of the matrix entries are generated by functions with very complex parameter lists. How can one conceal specific entries yet reveal meaningful statistics? How can one conceal some statistics yet reveal others? How can one detect attempts to subvert controls?