Keywords: Layered Protocols, Interface Design, Interaction Model

Perceptual control theory (PCT) is a framework theory for psychology, based on the tenet ?All behaviour is the control of perception.? Layered protocol theory (LPT) is PCT applied to the special case of communication between cooperating partners, each controlling their own perceptions and many levels of abstraction within a dialogue. This paper discusses some perceptual control processes that occur within a single dialogue level, in the form of a General Protocol Grammar that is asserted to be valid for every level of every dialogue. A companion paper is concerned with LPT applied to the design and analysis of human?machine interfaces