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<Paper uid="P91-1053">
  <Title>RESOLVING A PRAGMATIC PREPOSITIONAL PHRASE ATTACHMENT AMBIGUITY</Title>
  <Section position="3" start_page="0" end_page="352" type="metho">
    <SectionTitle>
3. The need to disambiguate
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    <Section position="1" start_page="0" end_page="351" type="sub_section">
      <SectionTitle>
3.1 Linguistic evidence
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      <Paragraph position="0"> Linguists have identified instrumental, locative and temporal adverbial PPs as the most structurally unrestricted, context-dependent types of PPs \[6, 10\]. These kinds of PPs often can attach either to S or VP. Thus, Warren sang in the park can be paraphrased as either Where Warren sang was in the park or What Warren did in the park was sing. Kuno argues that the former interpretation involves a place-identifying VP-PP, and the latter a scene-setting S-PP. Also, the following meaning differences occur: given-new/theme-rheme S-PPs are given/themes, VP-PPs are new/themes.</Paragraph>
      <Paragraph position="1"> preposability S-PPs can be preposed, preposed VP-PPs sound awkward and often change meaning.</Paragraph>
      <Paragraph position="2">  entailments S-PP utterances have no entailments of the utterance without the PP. For VP-PPs, the utterance without the PP is entailed only if the utterance is affirmative. null negation S-PPs always lie outside the scope of negation, VP-PPs may or may not lie inside the scope of negation. These aspects of meaning cannot be dismissed as spurious. Consider Kuno's pair of sentences: * Jim didn't visit museums in Paris, but he did in London (1).</Paragraph>
      <Paragraph position="3"> * Jim didn't visit museums in Paris: he visited museums in London (2).</Paragraph>
      <Paragraph position="4"> Kuno assigns (1) the interpretation in which'the PPs are sentential and two events are described: although Jim visited museums only in London, he also went to Paris. Sentence (2) is assigned the reading that Jim was not in Paris at all but went only to London where he visited museums. The PPs are verb-phrasal and only one event is being talked about.</Paragraph>
    </Section>
    <Section position="2" start_page="351" end_page="351" type="sub_section">
      <SectionTitle>
3.2 A pragmatic relation
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      <Paragraph position="0"> The behavior of these adverbial PPs reflects neither a complementation nor a modification relation. If attachment is dictated by complementation, an instrumental PP should always appear as an argument of the verb predicate in logical form. But this sacrifices entailments for affirmative VP-PP utterances; 'butter(toast,knife)' does not logically entail 'butter(toast)' \[2, 3\]. If construed as a modification relation, attachment is redundant with phrase structure information and curiously depends on whether the subject, or any other constituent outside the VP, is or is not modified by the PP. There may well be reasons to preserve these relations in the syrttactic structure, but they axe not the relations that desribd the behavior of pragmatically ambiguous PPs.</Paragraph>
      <Paragraph position="1"> The linguistic evidence suggests that the S-PP vs. VP-PP distinction reflects a pragmatic relation, namely a discourse entity specification relation where specify means to refer in a model \[4\]. Since this relation cannot be represented by traditional phrase structure trees, the meaning differences that distinguish the two kinds of PPs must be captured by a different formal structure. The proposed event formalism treats utterances with adverbial PPs as descriptions of events and  is adapted from Davidson's logical form for action sentences \[2\] using restricted quantification.</Paragraph>
      <Paragraph position="2"> 4. A unified formal account 4.1 Event representations Davidson's logical form consists of an existentially quantified event entity variable and predication, as in (3c)(Agt(Jones, e) A Act(butter, e) A Obj(toast, e) A Instr(knife, e)) for Jones buttered the toast with the knife. Davidson assigns equal  status to all modifiers, thereby allowing events, like objects and people, to be described by any combination of their properties. This flattening of the argument structure clears the way for using restricted quantification to 'elevate' some predicates to event-specifying status. Following \[12\], the structure 3eP restricts the range of e to those entities that satisfy P, an arbitrarily complex predicate of the form</Paragraph>
      <Paragraph position="4"> event-specifying predicates appear in the A-expression while the other predicates remain in the predication Re. Hereafter, the term event description refers to the ),-expression, and event predication to the sentence predicate Re. The two parts together comprise an event representation.</Paragraph>
    </Section>
    <Section position="3" start_page="351" end_page="352" type="sub_section">
      <SectionTitle>
4.2 Applying the formalism
</SectionTitle>
      <Paragraph position="0"> In the formalism, (3) represents sentence (1) and (4), (2):</Paragraph>
      <Paragraph position="2"> In (3), the thematic S-PPs (in bold) are represented in the event descriptions, whereas in (4), the nonthematic VP-PPs are in the event predications. Now the well-worn given-new distinction can be replaced by the more precise distinction made by the event formalism. Event-speci~ing PPs appear in the event description and contribute to the specification of an event entity in the discourse model. Predication PPs appear in the event predication and convey new information about the specified entity.</Paragraph>
      <Paragraph position="3"> The formalism shows how preposing a VP-PP can change the meaning of the utterance. If the PPs in (2) are preposed, as in In Paris, Jim didn't visit museums: in London, he visited museums, the original reading is lost. This is shown in the representation: --(Be : AuAgt( J, u) A Act(v, u) A</Paragraph>
      <Paragraph position="5"> Obj(m, u)ALoc(L, u)). Since the event descriptions conflictone event cannot take place in two places- this sentence can no longer be understood as describing a single event.</Paragraph>
      <Paragraph position="6"> The formalism also shows different effects of negation on event-specifying and predication PPs. Sentence (2) denies the existence of any 'Jim visiting museums in Paris' event, so the quantifier lies within the scope of negation in (4). In (3) negation scopes only the event predication; sentence (1) expresses a negative fact about one event, and an affirmative fact about another. In general, a PP that lies outside the scope of negation appears in the description Pu of a representation of form (3e : AuPu)-,\[Re\]. A PP that lies inside appears in the predication Re of form -,(3e : A,,P,,)\[Re\].</Paragraph>
      <Paragraph position="7"> Finally, the formalism lends insight into differences in entailments. The following entailment relationship holds for affirmative VP-PP sentences, where R,,(y,,, e) represents the</Paragraph>
      <Paragraph position="9"> A PP predicate Rn(yn,e) in a negated event predication may or may not be negated, so the entailment for negative VP-PP sentences is blocked: (Be: AnPu)'~\[Ra(ya, e) A... ^ Rn-i (yn-a, e) A Sn(y,,, e)\] ~ (Be: ~uPn)-,\[R1 (Yl, e) A... ^ Rn-l(y,-1, e)\]. Why S-PP sentences have no entailments is a separate matter. Eliminating an event-specifying PP from an event description yields a representation with a different description. Intuitively, it seems desirable that no entailment relations hold between different types of entities. The formalism preserves this condition.</Paragraph>
      <Paragraph position="10"> The proposed formalism succeeds in capturing the discourse entity specification relation and lends itself naturally to processing in an NLP system that takes seriously the dynamic nature of context. Such a system would for each utterance construct an event representation, search for a discourse entity that satisfies the event description, and use the event predication to update the information about that entity in the discourse model.</Paragraph>
    </Section>
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