• The complexity / compressibility approach. This paradigm was championed by A. N. Kolmogorov along with contributions Levin and Gregory Chaitin. For finite random sequences, Kolmogorov defined the "randomness" as the entropy, i.e. Kolmogorov complexity, of a string of length K of zeros and ones as the closeness of its entropy to K, i.e. if the complexity of the string is close to K it is very random and if the complexity is far below K, it is not so random.