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<Paper uid="E89-1006">
  <Title>TENSES AS ANAPHORA*</Title>
  <Section position="6" start_page="0" end_page="0" type="concl">
    <SectionTitle>
5 Conclusion and Problems
</SectionTitle>
    <Paragraph position="0"> The implemented system assigns DRSs to natural language texts in such a way that the partial event structure, substructure of the whole DRS, reflects the events and temporal relations of the story. The system is incomplete at present in the following respects: null The interaction of nominals and aspects is not accounted for.</Paragraph>
    <Paragraph position="1"> A principled treatment of tenses in embedded clauses is missing.</Paragraph>
    <Paragraph position="2"> The resolution of deictic/anaphoric temporal adjuncts is rudimentary.</Paragraph>
    <Paragraph position="3"> Knowledge about event types is at present not available to the Resolver.</Paragraph>
    <Paragraph position="4"> Thus the output event structure is generally underspecified. The integration of an inference component combined with background knowledge should restrict the number of possibilities to order the events linearly. In dependance of the Aktionsart the events of the DRS can be assigned subevents marking the boundaries of the event as suggested by Moens and Steedman(1986), (cf. Eberle(1988b)).</Paragraph>
    <Paragraph position="5"> These subevents can be regarded as having no temporal extension. Thus on the subevent-level before and equivalent exhaust the intuitive possibilities of temporal relations. By means of this finer granulation the (linear) event substructure of a DB.S corresponds to a unique (linear) interval structure provided the event relations before and overlap are defined in terms of Allen's interval structures (cf. Allen(1983)). Thus inferencing systems which deal with intervals, as the Allen system, become available but also systems which deal with point-like events as the event calculus of Kowalski/Sergot(1985). In addition we get the possibility to deal with temporal relations on different levels of precision.</Paragraph>
    <Paragraph position="6"> In Eberle(1988a) the possibilities of monotonic reasoning in partial event structures (in the sense of the Kowalski/Sergot-approach) were investigated.</Paragraph>
    <Paragraph position="7"> It is planned to extend the algorithm suggested there which adds deduced events to the structure, in order to deal with measure statements, knowledge about hierarchies of event types (e.g. subevent - 49 typologies) and temporal frames for event types (average duration of an event type). One aim is to rule out circular structures as mentioned in section 4.4. For simple cases we are able to do it yet. In such conflicting cases one has to backtrack to the Resolver, the Composer or the Parser to generate other readings. In this sense the suggested analysis system is non-monotonic since it generates other temporal relations if necessary. When finally a consistent reading has been arrived at, the event calculus can be used for non-monotonic reasoning, e.g.to deal with the problem of the validity of location times with respect to events localized before or after events for which an explicit relation of inclusion holds.</Paragraph>
  </Section>
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