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<Paper uid="C96-2153">
  <Title>Semantic Construction from Parse Forests</Title>
  <Section position="3" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> One of the most inl;eresting problems comes about by the tendency of natural language discourse to be ambiguous and open to a wide variety of interpretations. Generating representations for all the interpretations is nol, feasible in view of the strict computa|,ional bounds imposed on NLP systems. Instead, two other routes have been tmrsued: (1) the integration of further disambiguating knowledge and heuristics into the system or (2) the general;ion of a single semantic represent, alion that summarizes all the interI&gt;retations in the hope that the application task will force a distin&lt;:lion between the int;erpretations only in few cases. Such a summary repre.sentation is called under-specified if a procedure is given with it to &lt;terive a set of real semantic representations fl'om it. By now~ several techniques are kIlown to underspecify quantifier scope ambiguities (Alshawi, 1992), (Reyle, 1993). In this paper Discourse Representation Structures (Kamp mM Reyle, 1993) are employed as underlying semantic ret)resentations.</Paragraph>
    <Paragraph position="1"> For underspecification with respect to s&lt;:ope atnbigullies the present approach makes use of Under*This work was funded by the Germ;m Federal Ministry of Edu(:ation, Science, Research and Te(:hnology (BMBF) in the flamework of the Verbmobil Project under Grant 01. IV 1.01 U. Many thanks are due to M. Dorna, J. DSrre, M. Einele, E. KSnig-Bamner, C. Rohrer, C.J. Rupp, attd C. Vogel.</Paragraph>
    <Paragraph position="2"> speeilied Discourse Representation Theory (Reyle, 1993). Another strand of research has looked al; compact representations for parse outputs (Ear-Icy, 1970), (Tomita, 1985) and etticienI, parsing algorithms 1,o deliver such ret&gt;resentalions. Unfortunately, advances made in this area (lid not; have impact on semantic construction. It; was still necessary to first unpack the compacl; parsing ret)resentation and derive the individual parse trees from it before going about generating semant;ic representations. So in this area another applicalion for semantic underspecitieation is lurking.</Paragraph>
    <Paragraph position="3"> Several approaches to underspecifica|,ion axe conceival)le. (1) OperationM Underspecilical,ion: Construction operations that; involve art)itrary choices are delayed and carried out only on demand (Alshawi, 1992), (Pinkal, 1995). (2) I{epresentational Underspeeification: The ambiguil;ies are represented (explicitly or implicitly) in a forrealism. A resolution procedure derives the hillfledged semantic representations. This t)aper opts for the second approach (for motivation see chapter 7). hel,ween the t)arser and the semantic (:onsl;rllc|;ion colnponen|,~ (;oo.</Paragraph>
    <Paragraph position="4">  * Parse forests/charts (Alshawi, 1992).</Paragraph>
    <Paragraph position="5"> * Underspecified &amp;quot;trees&amp;quot; with abstract donfinanee information (Pinlml, 1.995).</Paragraph>
    <Paragraph position="6"> * Fully specified parse trees (Egg and Lebet;h,  1995). The syntactic ambiguities are ol)rained by re-ambiguat;ion in the semanl;ic eoHlponent.</Paragraph>
    <Paragraph position="7"> Our choice are parse forests since there are well-known methods of construction for t, hem and it is guarant;eed that every syntactic ambiguit;y can be represented in this way. ISu'thermore a wide range of existing parsing systems, e.g. (Block and Schachtl, 1992), produce packed representations of this kind.</Paragraph>
  </Section>
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