We have not considered the problems of formally describing the process of communication in this paper, but it seems clear that they will have to be tackled eventually. Philosophical logicians have been spontaneously active here. The major work is Harrah's book (1963); Cresswell has written several papers on `the logic of interrogatives', see for instance Cresswell (1965). Among other authors we may mention Åqvist (1965) and Belnap (1963); again the review pages of the Journal of Symbolic Logic will provide other references.
The research reported here was supported in part by the Advanced Research Projects Agency of the Office of the Secretary of Defense (SD-183), and in part by the Science Research Council (B/SR/2299).