2424	 Dynamic Verification of Operating System Decisions	 Dynamic verification of a decision implies that every time the decision is made there is a consistency check performed on the decision using independent hardware and software. The dynamic verification of operating system decisions is used on the PRIME system being designed and constructed at the University of California Berkeley. PRIME is an experimental time-sharing which is to have the properties of continuous availability data privacy and cost effectiveness. The technique of dynamic verification allows the construction of an operating system which does not make certain decisions improperly even in the presence of a single hardware or software fault. Furthermore multiple faults lead to unreliable operation only if the faults happen to reinforce each other. On PRIME dynamic verification is used to ensure that one user s information cannot become available to another user gratuitously even in the presence of a single hardware or software fault.the amount of additional hardware and software required for dynamic verification can be modest. operating systems data security fault tolerance software reliability data privacy program verification modular computer systems
