Generating Precondition Expressions in Instructional Text

GENERATING PRECONDITION EXPRESSIONS IN INSTRUCTIONAL TEXT Keith Vander Linden ITRI, University of Brighton Lewes Road Brighton, BN2 4AT UK Internet: knvl@itri.bton.ac.uk Abstract This study employs a knowledge intensive corpus analysis to identify the elements of the commu- nicative context which can be used to determine the appropriate lexical and grammatical form of instructional texts. IMAGENE, an instructional text generation system based on this analysis: is presented, particularly with reference to its ex- pression of precondition relations. INTRODUCTION Technical writers routinely employ a range of forms of expression for precondition expressions in instructional text. These forms are not randomly chosen from a pool of forms that say "basically the same thing" but are rather systematicaUy used based on elements of the communicative context. Consider the following expressions of various kinds of procedural conditions taken from a corpus of in- structional text: (la) If light flashes red, insert credit card again. (Airfone, 1991) l (lb) When the 7010 is installed and the battery has charged for twelve hours, move the OFF/STBY/TALK [8] switch to STBY. (Code-a-phone, 19891) (lc) The BATTERY LOW INDICATOR will light when the battery in the handset i~ low. (Excursion, 1989) (ld) Return the OFF/STBY/TALK switch to STBY a/ter your call. (Code-a-phone, 1989) (le) 1. Make sule the handset and base antennas are fully extended. 2. Set the OFF/STBY/TALK SWITCH to Talk. (Excltrsion, 1989) As can be seen here, procedural conditions may be expressed using a number of alternative l In this paper, a reference wiU be added to the end of all examples that have come directly from the corpus, indicating the ma~uual from which they were taken. lexical and grammatical forms. They may occur either before or after the expression of their related action (referred to here as the issue of slot), and may be linked with a variety of conjunctions or prepositions (the issue of linker). Further, they may be expressed in a number of grammatical forms, either as actions or as the relevant state brought about by such actions (called here the ter- minating condition). Finally, they may or may not be combined into a single sentence with the ex- pression of their related action (the issue of clause combining). Text generation systems nmst not only be ca- pable of producing these forms but must also know when to produce them. The study described here has employed a detailed corpus analysis to address these issues of choice and has implemented the re- sults of this study in IMAGENE, an architecture for instructional text generation. CORPUS ANALYSIS The corpus developed for this study contains ap- proximately 1000 clauses (6000 words) of instruc- tions taken from 17 different sources, including in- struction booklets, recipes, and auto-repair man- uals. It contains 98 precondition expressions, where the notion of precondition has been taken from Rhetorical Structure Theory (Mann and Thompson, 1988): and in particular from RSsner and Stede's modified relation called Precondition (1992). This relation is a simple amalgam of the standard RST relations Circumstance and Condi- tion and …

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