Shannon revisited: Information in terms of uncertainty

Shannon's theory of communication is discussed from the point of view of his concept of uncertainty. It is suggested that there are two information concepts in Shannon, two different uncertainties, and at least two different entropy concepts. Information science focuses on the uncertainty associated with the transmission of the signal rather than the uncertainty associated with the selection of a message from a set of possible messages. The author believes the latter information concept, which is from the sender's point of view, has more to say to information science about what information is than the former, which is from the receiver's point of view and is mainly concerned with “noise” reduction. © 1993 John Wiley & Sons, Inc.