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<Paper uid="P93-1011">
  <Title>NP VP Det N' V NP Det A</Title>
  <Section position="3" start_page="0" end_page="78" type="intro">
    <SectionTitle>
THE PROBLEM
</SectionTitle>
    <Paragraph position="0"> Because new ways of obtaining semantically distinct interpretations for sentences are continuously discovered, coming to grips with ambiguity is becoming more and more of a necessity for developers of natural language processing systems, linguists and psychologists alike \[9, 31, 7, 2\]. In this paper, I am concerned with the scopal ambiguity of operators I \[31, 33\].</Paragraph>
    <Paragraph position="1"> The attention of both psycholinguists and computational linguists interested in ambiguity has concentrated on the problem of combinatorial explosion. If the number of readings of an utterance were to actually grow with the factorial of the number of operators, even a simple sentence like (1), with 4 operators (the modal 'should', tense, an indefinite and a definite), would have 4I = 24 scopally different readings.</Paragraph>
    <Paragraph position="2"> Two distinct questions thus must be answered: how can listeners (and how should machines) deal with the combinatorial explosion of readings? Do we really use the brute-force strategy of considering all of the available readings, and then choose among them? And, if we do choose among several readings, how is that done? (1) We should hook up an engine to the boxcar.</Paragraph>
    <Paragraph position="3"> To my knowledge, three positions on the problem of combinatorial explosion have been taken in the literature. Some have argued that there is no problem: our brains contain  more than enough machinery to process in parallel 4I interpretations. It's unclear, however, whether this strategy is feasible when larger numbers of readings are concerned.</Paragraph>
    <Paragraph position="4"> A classical demonstration of the number of readings one may have to consider is (2), which has 1 l I interpretations if the standard treatment of quantification and modality is assumed.</Paragraph>
    <Paragraph position="5"> (2) You can fool most people on most of the issues most of the time, but you can't fool everybody on every single issue all of the time. \[15\] Another position is that sentences like (1) are not semantically ambiguous, but vague. Consider for example (3): (3) Every kid climbed a tree.</Paragraph>
    <Paragraph position="6"> Here, one of the readings (the one in which the indefinite takes narrow scope) is entailed by the other (in which the indefinite takes wide scope). The claim is that (3) is interpreted in the vaguest possible way, and the strongest reading, if at all, is derived by pragmatic 'strengthening' \[25\]. A difficulty with this approach is that a vaguest reading doesn't always exist. The two readings of (4), for example, are distinct. null  (4) Few people speak many languages. \[27\] Finally, it has been proposed that the reason why listeners do not seem to have problems in processing utterances like (1) is because they do not disambiguate. They build a non null disambiguated representation of the sentence and leave the interpretation open. This strategy might be advantageous for some kinds of applications 2 and it has been argued that a complete disambiguation never takes place \[7\].</Paragraph>
    <Paragraph position="7"> No matter what processing strategy is chosen, the question of how listeners choose one particular interpretation cannot be ignored. All experimental work done on the sub-ject of scopal ambiguity \[20, 35, 26\] indicates that subjects do have preferred interpretations when confronted with tasks which require understanding. In addition, sentences like (1), (5) and (6) clearly have preferred interpretations. However, the only answers to to this question that I have seen are based  (5) A girl took every chemistry course. \[20\] (6) Each daughter of an admiral married a captain.</Paragraph>
    <Paragraph position="8">  I present in this paper an hypothesis about interpretation that accounts for facts about scope disambiguation that were previously explained in the literature by stipulating a number of unmotivated principles. The proposal developed here is being applied to develop the module of the TRAINS-93 system \[1\] that handles scope disambiguation and reference interpretation. The goal of the TRAINS project is to develop a conversationally proficient planning assistant. More details about the project and the work presented here can be found in \[29\].</Paragraph>
  </Section>
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