Surface-level generation of tutorial dialogue using a specially developed lexical functional grammar and lexicon
Ru-Charn Chang · 1992
This thesis describes the design and development of a surface-level text generation system for an intelligent tutoring system for cardiovascular physiology, called CIRCSIM-TUTOR that assists first year medical students to master the negative feedback system that regulates blood pressure. Both the natural language understanding and the generation components of the system use a Lexical Functional Grammar and lexicon that I developed especially for the cardiovascular sublanguage. The grammar and lexicon are based on a detailed sublanguage study of human tutoring sessions. The system runs in Procyon Common Lisp on a Macintosh IICi. Most previous work on surface level generation has involved the generation of declarative sentences providing explanations in expert systems or answers to questions. To fill the needs of the tutoring dialogue, our system produces hints and questions and acknowledgments as well as explanations. Detailed algorithms are included for generating compound nominals and conjoined noun phrases and compound and complex sentences. My method of constructing relative clauses is different from any available in the literature. The Lexical Functional Grammar was developed using the Grammar Writer's Workbench developed at Xerox Palo Alto Research Center by Ronald Kaplan. The results of these tests have been implemented in the current text generator and the input understander. Lexical entries in published work about LFG contain too little information, therefore the design of a richer lexicon including semantic relationships between words is sketched. As far as we know, our grammar and lexicon are the largest coherent set of rules and lexical entries available for English. We are developing some linguistic techniques for making tutorial dialogue as natural as possible based on the data drawn from the transcripts. The sublanguage study is based on the analysis of seven face-to-face and twenty-eight keyboard-to-keyboard tutoring sessions carried out by faculty members at Rush Medical College with first year students. The result of our cardiovascular sublanguage study served as the basis for the design and construction of our surface level generation.