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<Paper uid="W91-0210">
  <Title>Lexical Structures for Linguistic Inference</Title>
  <Section position="3" start_page="0" end_page="102" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> Is a lexicon merely a set. of entry points into a conceptual, &amp;quot;real world&amp;quot; knowledge base, or does it have its own rich structure and rules of inference, related to, yet distinct from the body of world knowledge? Ill this paper, we explore this question from the point of view of the inferential machinery required to relate a verb and its arguments. We will argue that a rich lexical semantic structure makes it possible to express rules of composition with the degree of precision necessary to account for the many nuances of actual language use, capturing linguistic generalizations based on the semantic content of lexical items rather than relying solely on general purpose inferencing over an encyclopedic knowledge base.</Paragraph>
    <Paragraph position="1"> One of the fundamental properties of most computational lexicons is an accounting of the relationship between a verb and its arguments. Typically, each argument position of a verb is annotated with &amp;quot;selectional restrictions&amp;quot; which are intended to constrain the set of nouns which may legally fill the argument position 1. Such constraints are useful for word sense disambiguation, since semantically anomalous colnbinations of senses can be readily identified and discarded during parsing.</Paragraph>
    <Paragraph position="2"> A number of researchers have noted that such selectionai restrictions may legitimately be violated under certain circumstances, as ill the sentences below:  (1) &amp;quot;The car drank gasoline.&amp;quot; (\[Wilks, 1978\]) (2) &amp;quot;Ted played Bach.&amp;quot; (\[Fass, 1988\]) 1 If nouns are organized into a conceptual &amp;quot;isa&amp;quot; hierarchy, then a selectlonal restriction may be no more than a reference to a position in the hierarchy.</Paragraph>
    <Paragraph position="3">  In (1), the &amp;quot;car&amp;quot; violates the selectional restriction that the subject be animate. In (2), the object &amp;quot;Bach&amp;quot; is a person, violating the verb's selectional restrictions (i.e. some form of music). Following \[Wilks,1978\], Fass \[1988\] interprets selectional restrictions as preferences and goes on to account for violations of preferences via operations such as metonymy and metaphor. For example, Fass postulates a number of metonymic substitution rules, such as &amp;quot;Artist for Artform&amp;quot;, &amp;quot;Container for Contents&amp;quot;, and &amp;quot;Part for Whole.&amp;quot; When a preference violation is encountered, his algorithm tries applying these metonymic inference rules to the offending noun in an attempt to find the &amp;quot;shortest&amp;quot; coherent path between the verb's preference and some metonymically related concept. Failing this, the algorithm goes on to explore metaphorical interpretations. In a similar vein, \[Parisi and Castelfranchi, 1988\] make use of a semantic network encoding &amp;quot;encyclopedic&amp;quot; relations among lexical concepts to derive paths between verbs and arguments which violate selectional restrictions. Using a shortest path heuristic, their algorithm interprets the senetence &amp;quot;The pot is boiling.&amp;quot; as &amp;quot;The liquid which is contained in the pot is boiling.&amp;quot; While these algorithms work well on a small set of interesting examples, we feel that distance metrics operating on unconstrained encyclopedic knowledge insufficiently characterize the relationship between lexical entries and metonymic inference. In this paper, we present a richer representational framework for lexical knowledge, based on Generative Lexicon theory \[Pustejovsky, 1991\], and describe a methodology for exploring the interplay between word senses and the metonymic processes they enter into. \[Pustejovsky 1991\] distinguishes between &amp;quot;logical metonymy&amp;quot;, whose resolution falls naturally out of operations on information contained directly in lexical entries, and &amp;quot;pragmatic metonymy&amp;quot;, whose resolution depends on interpretation with respect to the proper pragmatic context. We begin with an overview of the major components of Generative Lexicon theory and present data from the semantic domain of musical terms to illustrate how metonymic reasoning is facilitated in a generative lexicon. Then we indicate how in the case of reporting verbs the compositional semantics of the matrix verb and the subject produce pragmatic constrains on the complement. We conclude that it is advantageous to represent the conceptual knowledge that bears on the linguistic behavior of words in the lexicon.</Paragraph>
  </Section>
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