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<Paper uid="E89-1030">
  <Title>A MODULAR APPROACH TO STORY GENERATION</Title>
  <Section position="3" start_page="0" end_page="0" type="metho">
    <SectionTitle>
TEXT TYPES
</SectionTitle>
    <Paragraph position="0"> 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).</Paragraph>
    <Paragraph position="1"> Often, especially in &amp;quot;realistic&amp;quot; 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 - 217processing 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.</Paragraph>
    <Paragraph position="2"> Text types interact in complex ways with the other categorial features of texts, such as content, speaker type, speech situation, register and speech act identity. Sometimes, text types are highly constrained in this regard. For example, conventionally a text of the &amp;quot;sermon&amp;quot; genre is uttered in the &amp;quot;church service&amp;quot; speech situation, in a formal register: it is normally produced only by a priest-figure, and often serves as a &amp;quot;warning&amp;quot; or &amp;quot;exhortation&amp;quot; speech act. Texts of the story genre are not tightly linked to any such characteristics: they may be expressed by anyone, in any register, in almost any speech situation, and, while their illocutionary force is essentially &amp;quot;assertion&amp;quot;, their intended perlocutionary forces may be many and varied. However, sub-genres such as the detective story, the narrative ballad, the traditional folk tale and so on, will impose further constraints of their own.</Paragraph>
    <Paragraph position="3"> A MODEL OF STORY GENERATION As this discussion of genre theory implies, story structure cannot be discussed in isolation from a variety of other constraints. A theory of story structure for the purposes of text generation must be situated within a broader theory of story production, which can perhaps best be described in terms of the sorts of knowledge which contribute to the creation of a story. A full story generating system would need access to many different kinds of separate but interacting knowledge. These would include knowledge of:  (a) story structure Co) the audience (c) the author (d) the cultural context (e) the rules of the sub-genre  Knowledge of the audience will influence what information should be included in the text and what can be taken as read. Characteristics of the author may lead, for instance, to choices which give a particular perlocutionary force to the text: a moralist might insist on a fictional wrongdoer coming to a sticky end, where a cynic might let him/her go unpunished. The cultural context refers to the socio-historical setting in which the text is produced, which restricts the particular sub-genres available: tales of saints' lives, for instance, all the rage in the Twelfth Century, are now out of vogue and so virtually &amp;quot;untellable&amp;quot;. The rules of the sub-genre will place constraints not only on the content of the text, but also on the choice of expressive medium and on stylistic choices within the expressive medium: verse will be fine for a narrative ballad, inappropriate for a detective story. It is knowledge of types (a) and (e) which is encoded in the grammar of the Old French epic described below.</Paragraph>
    <Paragraph position="4"> A STORY GRAMMAR FOR THE EPIC The study reported in (Pemberton, 1984) is an attempt to identify a general model of story structure, as well as the additional constraints on the form and content of a particular subgenre, the mediaeval French epic. Nine poems composed in mediaeval France, concerning the adventures of a family of French Christian fighters, were analysed and their narrative structure described in terms of a grammar.</Paragraph>
    <Paragraph position="5"> It was found necessary to distinguish between various levels of analysis of the text. The textual level is that which the reader experiences directly: in the poems in question, a textual element might be &amp;quot;Guillelmes vit Cation&amp;quot; (Guillaume saw Charles). The textual level, which is not included in the study, may be thought of as the lexicalised version of the layer of analysis referred to as discourse. This is in turn a modified version of the story line, where the story line is the succession of all the events in a story, and discourse consists of these same events restructured into a form - 218 suitable for telling. The story line of a detective story, for instance, would recount the crime and its detection in chronological sequence, while the discourse ordering might begin instead with the discovery of the crime. While discourse and story line differ in structure relative to each other, they share the same elements, which consist of propositions formed of events and actors. A typical discourse/storyline element might be &amp;quot;saw(Guillaume, Charles)&amp;quot;. The highest level of analysis, the narrative model, is the abstract form of the story line. Units at this level are as free of content as possible, and consist of combinations of functions and roles. The set of functions in the grammar includes elements such as &amp;quot;cause,&amp;quot; &amp;quot;succeed&amp;quot; and &amp;quot;attempt&amp;quot;, while roles are case-like notions such as &amp;quot;subject,&amp;quot; &amp;quot;beneficiary&amp;quot; and &amp;quot;opponent&amp;quot;. The narrative model is a construct applicable to many different types of story, whereas units of discourse and storyline will be peculiar to the genre in question.</Paragraph>
    <Paragraph position="6"> NARRATIVE Information about story structure takes the form of a grammar, whose starting symbol is complex stories. A complex story consists of one or more simple stories. Two stories may be combined using any of four links: these are cause, where the first story causes the second; motive, where a particular action of the first story motivates the second; then, where all the active elements of one story follow all the active elements of the other, and same actor, where there is merely sharing of one or more actors.</Paragraph>
    <Paragraph position="7"> The simple story is expanded into an initial situation, an active event, and a final situation. Semantic restrictions on the initial situation state that it must involve two roles, subject and object or object class, in a relation of lack, while the final situation must consist of a negation or restatement of the initial lack. The active event consists of an event in which the subject (or a surrogate) attempts to obtain the object, or a member of the object class. Each element is linked to the next by succession in time, while final situation is linked to the active event in a causal relationship.</Paragraph>
    <Paragraph position="8"> The active event is expanded into a five-part structure consisting of motivation, plan, qualification, action, and resolution. The motivation phase consists of the process whereby the subject or surrogate subject acquires the will to bring an end to the initial situation by means of some action. There are two types of motivation: general motivation looks back to the initial situation, while specific motivation looks forward to the action which will end the initial situation. An everyday example will illustrate this distinction: a person who is hungry will have a general motivation to end that state of hunger, but only when confronted with the sight of, say, a loaf of bread, will s/he acquire the specific motivation to end the undesirable state by an action. The stimuli which bring about general and specific motivation are referred to as motivating acts.</Paragraph>
    <Paragraph position="9"> The plan phase consists of the subject's acquisition of the knowledge needed to perform the main act: this knowledge is acquired via one or more informing acts.</Paragraph>
    <Paragraph position="10"> Similarly, qualification is the process of acquiring the power, material or physical, to carry out the main act, via a series of qualifying acts. The action is the subject's attempt to obtain the object, while resolution is the phase in which the success or failure of the action is made clear, determining whether the final situation is to be a negation or a reaffirmation of the initial state. Within tiffs scheme, recursion allows for several attempts to be made on the same goal, or for a new goal to be set.</Paragraph>
    <Paragraph position="11"> The terminal elements of this grammar of the narrative model are narrative motifs, which, when instantiated, will make up the chronological flow of the text. It is these motifs which provide the answer to the question &amp;quot;What happened next?&amp;quot; in the story. - 219 -However, few real-life story texts could be described in terms of the bare minimum of propositions generated by the grammar as sketched so far: much more richness of detail is required. The grammar allows for this extra detail by permitting any element of the active event to be supplemented by other narrative motifs, of two types, tied or free. Tied narrative motifs are those which expand elements generated by the narrative model: a qualifying act, for instance, may be expressed in several steps, or several motivating acts may take place. However, even the simplest narrative text contains representations of events which, while not deriving from the narrative model, still describe what happened next (cf. Shen, 1988). These are free narrative motifs, which may illustrate character, exemplify themes, create irony, suggest an historical setting, and so on (cf. Barthes, 1970). Particularly important for the epic is the opposition motif, which serves to hinder, jeopardise or delay some element of the active event.</Paragraph>
  </Section>
  <Section position="4" start_page="0" end_page="0" type="metho">
    <SectionTitle>
STORY LINE
</SectionTitle>
    <Paragraph position="0"> The movement between the elements of the narrative model and those of the story line may be seen essentially as a process of instantiation, detailing which types of actors from the story world of the genre may fill which roles, and which types of events may serve which functions. For reasons of space, the reader is referred to (Pemberton, 1984) for details of the epic story world.</Paragraph>
  </Section>
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