Stratification and enumeration of Boolean functions by canalizing depth

TL;DR

This paper introduces a novel algebraic framework to classify all Boolean functions by their canalizing depth, providing a comprehensive enumeration and structural understanding relevant to systems biology.

Contribution

It generalizes existing algebraic structures for nested canalizing functions and offers explicit formulas for counting functions by canalizing depth.

Findings

Every Boolean function has a unique algebraic form involving extended monomial layers.

The paper provides closed-form formulas for counting Boolean functions with a given canalizing depth.

It extends enumeration results from canalizing to all Boolean functions.

Abstract

Boolean network models have gained popularity in computational systems biology over the last dozen years. Many of these networks use canalizing Boolean functions, which has led to increased interest in the study of these functions. The canalizing depth of a function describes how many canalizing variables can be recursively picked off, until a non-canalizing function remains. In this paper, we show how every Boolean function has a unique algebraic form involving extended monomial layers and a well-defined core polynomial. This generalizes recent work on the algebraic structure of nested canalizing functions, and it yields a stratification of all Boolean functions by their canalizing depth. As a result, we obtain closed formulas for the number of n-variable Boolean functions with depth k, which simultaneously generalizes enumeration formulas for canalizing, and nested canalizing functions.