Protosynthex III (PSIII) is a language processing system developed as an (as yet inadequate) experimental vehicle for testing student responses, with a view to constructing a model of an automated tutor. A version of the PLANIT system was modified so that a human tutor could be used to make instructional decisions in response to students' constructed answers to questions presented by PLANIT, and the resulting interactions used as examples of the breadth of language that the language processor eventually must straddle. The project is based on two interdependent assumptions yet untested: that the model will be effective as a teaching instrument (it demands from the student greater subject mastery); and that it can be constructed as a working computer system. The automated model is fed with a correct answer which is just sufficient to satisfy the query--the canonical answer (CA). The model then takes the student response (SR) and compares it with the CA. There are five possible relationships between the CA and the SR, ranging from equipollent, through partially irrelevant, to totally irrelevant, and the model directs the student accordingly. The automated tutor is still in its infancy, and a great deal of work is foreseen before it becomes a useful system. (GO)