This paper presents Strong Dependency, a formalism based on an information theoretic approach to information transmission in computational systems. Using the formalism, we show how the imposition of initial constraints reduces variety in a system, eliminating undesirable information paths. In this way, protection problems, such as the Confinement Problem, may be solved. A variety of inductive techniques are developed useful for proving that such solutions are correct. Section 1, INTRODUCTION

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... rs of large computational systems require assurances that information they deem private remains private. Recent work (e.g. [Denning 76, Walters 75]) has used a notion of "information flow" in order to formally state such assurances. If, for each operation provided at some level of a system, one can determine the information flow resulting from that operation -inductive techniques can be used to determine the extent of information transmission in the system as a whole.