Claude Elwood Shannon in 1948, then of the Bell Labs, published one of the ground breaking papers in the history of engineering [1]. This paper (”A Mathematical Theory of Communication”, Bell System Tech. Journal, Vol. 27, July and October 1948, pp. 379 - 423 and pp. 623 - 656) laid the groundwork of an entirely new scientific discipline, information Theory, that enabled engineers for the first time to deal quantitatively with the elusive concept of information”. In his celebrated work, Shannon cleanly laid the foundation for transmission and storage of information. Using a probabilistic model, his theory helped to get further insight into the achievable limits of information transfer over perturbed medium called channel. Indeed the very same concept is used to predict the limits on data compression and achievable transmission rate on a probabilistic channel.These underlying concepts can be thought of as inequalities involving measures of probability distributions. Shannon defined several such basic measures in his original work. The field of Information Theory grew with researchers finding more results and insights into the fundamental problem of transmission of and storage using probabilistic models. By nature of the subject itself, the results obtained are usually inequalities involving basic Shannon’s measures such as entropies. Some of them are elementary, some rather complicated expressions. In order to prove further theorems as well it required to check whether certain expressions are true in an Information Theoretic sense. This motivated researchers to seek a formal method to check all possible inequalities. Raymond Yeung [2] in 1998 came out with a remarkable framework, which could verify many of the inequalities in this field. His framework thus enabled to verify all inequalities, derived from the basic Shannon measure properties. A central notion of Information Theory is entropy, which Shannon defines as measure of information itself. Given a set of jointly distributed random variables X1, X2, . . . , Xn, we can consider entropies of all random variables H(Xi), entropies of all pairs H (Xi , Xj ), etc. (2n − 1 entropy values for all nonempty subsets of {X1 , X2 , ..., Xn }). For every n-tuple of random variables we get a point in R2n−1, representing entropies of the given distribution. Following [2] we call a point in R2n−1 constructible if it represents entropy values of some collection of n random variables. The set of all constructible points is denoted b y Γ ∗n It is hard to characterize Γ∗n for an arbitrary n (for n ≥ 3, it is not even closed [?]). A more feasible (but also highly non- trivial) problem is to describe the closure Γ ̄∗n of the set Γ∗n. The set Γ ̄∗n n is a convex cone [?], and to characterize it we should describe the class of all linear inequalities of the form λ1H(X1) + . . . + λnH(Xn) + λ1,2H(X1X2) + . . . + λ1,2,3H(X1, X2, X3) + . . . + λ1,2,3,...,nH(X1, X2, X3, . . . , Xn) which are true for any random variable
