Hierarchical approach to computer system integrity
John J. Donovan, Stuart Madnick · IBM Systems Journal · 1975
In this paper, we have shown how a hierarchically structured operating system can provide substantially better software reliability and security than a conventional two-level multiprogramming operating system approach. A virtual machine facility, such as VM/370, makes it possible to convert a two-level conventional operating system into a three-level hierarchically structured operating system. Furthermore, by using redundant security mechanisms, a high degree of security is attainable.