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<Paper uid="W93-0220">
  <Title>References</Title>
  <Section position="2" start_page="71" end_page="72" type="abstr">
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(PREFER-THEMATIC-PRO GRESSION theme-theme)
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    <Paragraph position="2"> The selection of the relation ID-SEQUENCE, which is typically employed to link chronological events, triggers three follow-up actions: * an event is selected fi'om the knowledge base which stands in a succession relationship to the event which has just been mentioned. Also, relevant inibrmation linked to that &amp;quot;new&amp;quot; event (actors, temporal features) has to 1)e retrieved (SELECT-KNOWLEDGE); * a certain pattern of thematic progresskm, which is th.vored by the relation at hand, is determined. In example 2 above, the theme of the chronologically linked sentences is the same (&amp;quot;water&amp;quot;) throughout the whole text (function HtEFE a-Tll EM aTlC-PltO(~ rtESSlON); * the text plan is incremented by the new information and linked to the preceding context by means of the relation ID-SEQUENCE (GROW-TREE).</Paragraph>
    <Paragraph position="3"> In a similar way, the effect of choosing a commuMcative goal imposes constraints on the document planning environment. Depending on the type of goal, various realization statements are executed. We distinguish (1) goals responsible for the generation ot' text segments and (2) goals contributing to the choice of medium and presentation form of an utterance. We will give an example for each:  The goals related to the production of text, of which our first example is an instance, can induce the following realization statements: * if the text unit can be coml)osed of fiu'ther subtexts and if there are subgoals availahle to represent these text units they have to be pushed on a goal stack in the order they are supposed to appear in the text (PUSH-ON-GOAL-STACK).</Paragraph>
    <Paragraph position="4">  * the relations which are typically used in the text units represented by the goal have to be marked as preferable (HIGHLIGHT-RELATIONS).</Paragraph>
    <Paragraph position="5"> . with every change of the communicative goal, the global topic to be dealt with changes accordingly. This change in topic is brought about by the function CHANGE-TOPIC. In terms of the text planning process this flmction determines the hub fl'om which the generation of this new segment has to be started. The hub represents the instance, where tim knowledge selection and the navigation in the knowledge base with respect to the text unit starts.</Paragraph>
    <Paragraph position="6"> . where possible thematic progression is determined by means of rhetorical relations; if tim context is empty and there is no relation available - for example when a new text unit is generated - or if thematic progression cannot be constrained by the relation chosen the default focus of the paragraph as specified by PREFER-FOCUS is taken.</Paragraph>
    <Paragraph position="7"> Goals concerned with the choice of the best way to l)resent intbrlnation activate only one . type of realization statements, which restrict the presentation types to be chosen (PR.EFErtPRESENTATION-TYPE). null Based on these ideas a new component for the treatment of communicative goals in the framework of Multimedia Document Generation has been developed. This component integrates goals necessary for text planning with intentions ernployed by the so-called 'Pragmatic Model', which flllfills the task of a presentation planner. This builds on experience developed with the AlFresco project (\[Stock et al., forthcoming\]).</Paragraph>
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