A COMPREHENSIVE MODEL OF LANGUAGE SHOULD ACCOUNT FOR ENTIRE DISCOURSES. BY REGARDING THE UNDERLYING STRUCTURE OF DISCOURSE AS A COLLECTION OF TREES GENERATED BY A PREDICATE GRAMMAR AND RELATED TO EACH OTHER ON THE BASIS OF FOCUS, IT APPEARS POSSIBLE TO FIT A MODEL TO LINGUISTIC BEHAVIOR BOTH ABOVE AND BELOW THE LEVEL OF THE SENTENCE. THE BASE OF GRAMMAR IS BUILT AROUND POINTS WHERE DECISIONS, BOTH DETERMINISTIC AND STOCHASTIC, CAN BE MADE. THE TRANSFORMATIONS OF GRAMMAR THEN CORRESPOND TO PATTERNS OVER WHICH SPEAKERS HAVE NO DIRECT CONTROL. THE MODEL HAS IMPLICATIONS FOR THE WAY IN WHICH THE STRUCTURE OF PARTICULAR DISCOURSES CAN BE INVESTIGATED. (AUTHOR/DO)