A Modular Approach to Story Generation

A MODULAR APPROACH TO STORY GENERATION Lyn Pemberton School of Cognitive and Computing Sciences University of Sussex Falmer~ Brighton BN1 9QN United Kingdom ABSTRACT One way of characterising texts is in terms of the discourse structures on which they appear to be built. Each type of text, or genre, e.g. the sports report, the recipe, the sermon, the proverb, will have associated with it a characteristic organisation of units. In this paper, a general model of the structure of one text type, the story, is described. This model forms the basis of a program which combines the general story structure principles with rules goveming a particular sub-genre, the Old French epic, in order to generate story summaries. INTRODUCTION Over the last twelve years, research in Psychology and AI into narrative structure has been marked by acrimonious disputes over the right to existence of the "story grammar" approach. The point at issue is whether it is possible, as story grammarians suggest, to identify structural regularities particular to narrative texts (Mandler and Johnson, 1980; Pemberton, 1987; Shen, 1988), or whether any structural regularities should be interpreted rather as world knowledge, usable in contexts other than stories (Gamham, 1983; Wilensky, 1980; Yazdani, 1982). The work described in this paper adopts the story grammarian position, arguing that a general model of story structure may be used, in conjunction with, but separate from, a model of the "story world", to generate stories. Moreover, a fuller version of such an account of story generation must draw not only on the general story structure model and the story world model, but also on aspects of the audience, the author, the medium of expression and the cultural context. TEXT TYPES People are able to categorise texts into types, according to the global conditions of coherence which they perceive at work in texts. Knowledge of the particular structures of each text type is an element of the cultural competence of the speaker/hearer, enabling him/her to process varieties of cultural artefact such as jokes, sermons, weather reports, sets of instructions and so on, in appropriate ways (Ryan, 1981). Often, especially in "realistic" texts, it may seem that these conditions of coherence are reducible to the everyday concepts which we use to analyse aspects of the real world, especially notions such as plans, goals and intentions. On the other hand, the fact that the same real world events, e.g. a road accident, or a bank robbery, may be represented in texts of widely different types, such as a newspaper article, a telegram message, a joke, or a conversational anecdote, indicates that structuring models, in addition to those imposed by the structure of the content, are at work in texts. Such models facilitate the - 217- processing of texts, creating certain expectations when we recognise a text as an instance of a particular genre, and providing a set of patterns to guide the creation of new instances. Text types interact in complex ways with the other categorial features of texts, such as …

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