Optimal Coding in the Case of Unknown and Changing Message Statistics

A coding method is proposed which is independent of the message probabilities and permits a compression of the messages corresponding to their redundancy, without a knowledge of the statistical laws responsible for this redundancy. Sufficient conditions are formulated for optimality of coding in this sense. It is pointed out how results of this kind may be generalized to a noisy channel, in the sense of obtaining optimal methods of transmitting over such channel messages which are independent of the statistics of the message source.