Many modern operating systems and applications focus on functionality not security. Type enforcement is a mechanism that when properly implemented in the operating system can combine high security and functionality. The paper describes how type enforcement can be used to achieve both of these important requirements. The paper also describes a specific implementation of type enforcement, the Sidewinder Internet firewall.
"Type enforcement: the new security model", Proc. SPIE 2617, Multimedia: Full-Service Impact on Business, Education, and the Home, (19 January 1996); doi: 10.1117/12.230418; https://doi.org/10.1117/12.230418