We provide a retrospective view of the design of SRI's Provably Secure Operating System (PSOS), a formally specified tagged-capability hierarchical system architecture. It examines PSOS in the light of what has happened in computer system developments since 1980, and assesses the relevance of the PSOS concepts in that light.
['Peter G. Neumann', 'Richard J. Feiertag']
PSOS revisited