Elaboration in Object Descriptions Through Examples

ELABORATION IN OBJECT DESCRIFFIONS THROUGH EXAMPLES Vibhu O. Mittal Department of Computer Science University of Southern California Los Angeles, CA 90089 USC/Information Sciences Institute 4676 Admiralty Way Marina del Rey, CA 90292 Abstract Examples are often used along with textual descrip- tions to help convey particular ideas - especially in instructional or explanatory contexts. These accompa- nying examples reflect information in the surrounding text, and in turn, also influence the text. Sometimes, examples replace possible (textual) elaborations in the description. It is thus clear that if object descriptions are to be generated, the system must incorporate strate- gies to handle examples. In this work, we shall inves- tigate some of these issues in the generation of object descriptions. INTRODUCTION There is little doubt that people find examples very ben- eficial in descriptions of new or complex objects, rela- tions,orprocesses. Various studies have shown that the inclusion of examples in instructional material signifi- cantly increases user comprehension (for e.g., (Houtz, Moore & Davis, 1973; MacLachlan, 1986; Pirolfi, 1991; Reder, Charney & Morgan, 1986; Tennyson & Park, 1980)). Users like examples because exam- pies tend to put abstract, theoretical information into concrete terms they can understand. Few generation systems have attempted to make significant use of ex- amples, however. In particular, most systems have not integrated examples in the textual descriptions, but have used them mostly on their own, independently of the explanation that may also have been provided at that point. However, examples cannot be generated in isolation, but must form an integral part of the descrip- tion, supporting the text they help to illustrate. Most previous work (especially in the context of tutoring systems) focused on the issue offinding useful examples (for e.g., Rissland's CEG system (1981) and Ashley's HYPO system (Ashley, 1991; Rissland & Ashley, 1986; Rissland, 1983)). Work by Woolf and her colleagues considered issues in the generation of tu- torial discourse, including the use of examples (Woolf & McDonald, 1984; Woolf & Murray, 1987), but their 315 analysis did not address specific issues of integrated example and language generation. In this paper, we build upon some of these stud- ies and describe the issues in generating descriptions which include examples in a coordinated, coherent fashion, such that they complement and support each other. AN EXAMPLE Consider for inst,'mce, the example in Figure 1, from a well known introductory book on the programming language LISP. It describes an object (a data structure) called a "fist." There are a number of issues that can be immediately seen to be relevant: I. Should the system choose to elaborate on the object attributes in text, or through the use of examples? For instance, the information in Figure I could also have been expressed textually as: "A list always be- gins with a left parenthesis. Then come zero or more pieces of data (called the elements of a list), and a right parenthesis. Data elements can be of any LISP type, including numbers, symbols and strings". In the figure, the examples arc …

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