Designed to minimize information overload in telecommunications systems, the formal model developed in this paper predicts the usefulness of a message based on the available message features, and may be used to rank messages by expected importance or economic worth. The assumptions of binary and two Poisson independent probabilistic distributions of message feature frequencies are examined, and methods of incorporating these distributions into the ranking model are considered. Ways to incorporate user supplied relevance feedback are suggested, and analytic performance measures are proposed to predict system quality. Problems with this formal model are examined, and areas of future research are suggested. The text is supplemented by two tables and one figure. (33 references). (Author/EW)