A generalization of Shannon function

When investigating the complexity of implementing Boolean functions, it is usually assumed that the basis in which the schemes are constructed and the measure of the complexity of the schemes are known. For them, the Shannon function is introduced, which associates with each Boolean function the least complexity of implementing this function in the considered basis. In this paper we propose a generalization of such a Shannon function in the form of an upper bound that is taken over all functionally complete bases. This generalization gives an idea of the complexity of implementing Boolean functions in the "worst" bases for them. The conceptual content of the proposed generalization is demonstrated by the example of a conjunction.