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<Paper uid="W06-0904">
  <Title>Sydney, July 2006. c(c)2006 Association for Computational Linguistics A Pilot Study on Acquiring Metric Temporal Constraints for Events</Title>
  <Section position="10" start_page="69" end_page="69" type="concl">
    <SectionTitle>
8 Conclusion
</SectionTitle>
    <Paragraph position="0"> This paper describes the first steps in acquiring metric temporal constraints for events. The work is carried out in the context of the TimeML framework for marking up events and their temporal relations. We have identified a method for enhancing TimeML annotations with metric constraints. Although the temporal reasoning required to carry that out has been described in the prior literature, e.g., (Kautz and Ladkin 1991), this is a first attempt at lexical acquisition of metrical constraints. As a pilot study, it does suggest the feasibility of acquisition of metric temporal constraints from corpora. In follow-on research, we will explore the enhancements described in Section 7.</Paragraph>
    <Paragraph position="1"> However, this work is limited by the lack of evaluation, in terms of assessing how valid the durations inferred by our method are compared with human annotations. In ongoing work, Jerry Hobbs and his colleagues (Pan et al. 2006) have developed an annotation scheme for humans to mark up event durations in documents. Once such enhancements are carried out, it will certainly be fruitful to compare the duration probabilities obtained with the ranges of durations provided in that corpus.</Paragraph>
    <Paragraph position="2"> In future, we will explore both regression and classification models for duration learning. In the latter case, we will investigate the use of constructive induction e.g., (Bloedorn and Michalski 1998). In particular, we will avail of operators to implement attribute abstraction that will cluster durations into coarse-grained classes, based on distributions of atomic durations observed in the data. We will also investigate the extent to which learned durations can be used to constrain TLINK ordering.</Paragraph>
  </Section>
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