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<Paper uid="P85-1025">
  <Title>Some Pragmatic Issues in the Planning of Definite and Indefinite Noun Phrases</Title>
  <Section position="3" start_page="198" end_page="198" type="metho">
    <SectionTitle>
2 Research Objectives
</SectionTitle>
    <Paragraph position="0"> The analysis presented in this paper represents one of the first steps toward a plan-based account of definite and indefinite noun phrases. Ideally, such an account would (1) provide a semantics for noun phrases, (2) define an actions like &amp;quot;uttering a definite noun phrase, ~ and (3) provide an analysis that shows how the speaker's intentions follow directly from the semantics of the noun phrase he utters, plus conditions on mutual knowledge and general principles of rationality. This program is very much in the spirit of the analysis of illocutionary acts provided by Cohen and Levesque (1980), who demonstrate how illocutionary acts can be defined in terms of the kinds of inferences made, given a semantic analysis of an utterance, facts about mutual knowledge, and general principles of rational behavior.</Paragraph>
    <Paragraph position="1"> Cohen ( 1984} provided such an analysis for referring actions by postulating a semantics for the definite determiner that would give the semantics of a definite noun phrase as a request to identify the referent of a description. This analysis would be impossible to extend to the more general concept activation actions, because, in some cases, the speaker intends that the hearer not identify the denotation of the description, even when a definite noun phrase is used. A complete analysis along these lines that subsumes both referring and nonreferring noun phrases has yet to be worked out.</Paragraph>
    <Paragraph position="2"> As an intermediate step toward this ultimate goal, we shall propose a taxonomy of concept activation actions that convey the various intentions a speaker may have with respect to a hearer and a description. This taxonomy is of theoretical interest, because it characterizes differences and similarities among uses of noun phrases that current theories do not characterize. It is also of practical interest for utterance planning, because the set of actions to be proposed provides a useful level of abstraction for the reasoning processes of an utterance-planning system. For example. certain planning strategies such as action subsumption {Appelt. 1985} axe applicable only to certain kinds of concept activation actions and not to others. Therefore, even if the complete plan-based analysis of noun ph~ is worked out, the taxonomy of actions presented here will still be of practical importance.</Paragraph>
    <Paragraph position="3"> Until an analysis like Cohen and Levesque's is worked out, the concept activation actions here will be treated like illocutionary acts in a speech-act theory. When a hearer understands an utterance, he reasons about whether it constitutes an assertion, a request, a warning, etc. Therefore, understanding one of the definite or indefinite noun phrases under consideration in this paper is assumed to entail recognition of what concept activation action the speaker intends to perform.</Paragraph>
  </Section>
  <Section position="4" start_page="198" end_page="199" type="metho">
    <SectionTitle>
3 Summary of Actions Underlying
</SectionTitle>
    <Paragraph position="0"/>
    <Section position="1" start_page="198" end_page="199" type="sub_section">
      <SectionTitle>
Noun Phrases
</SectionTitle>
      <Paragraph position="0"> There are many distinctions that one could draw between noun phrases, only some of which are relevant to planning.</Paragraph>
      <Paragraph position="1"> For example, one could distinguish noun phrases that refer to amorphous substances from those that refer to discrete entities. Such a distinction may have some valid motivation, but it is not necessarily so from the standpoint of planning. It would be well motivated only if there were a clear difference in the preconditions and effects of the concept activation actions-underlying mass terms, or in the strategy for the selection of descriptors. This does not seem to be the case for mass versus discrete entities.</Paragraph>
      <Paragraph position="2"> However, there are two criteria that clearly affect the relevant preconditions, intended effects, and planning strategies of concept activation actions: {l) whether the speaker intends that the hearer identify the denotation of the description, and {2) how much mutual knowledge the speaker and hearer share about the description's denotation. The first criterion is what {roughly} distinguishes referring noun phrases from nonreferring noun phrases. The necessity, of the hearer performing the identification constrains the description to be one that facilitates the hearer's formulation of a plan to do so.</Paragraph>
      <Paragraph position="3"> The second criterion is the knowledge that is shared by the speaker and the hearer at the time of the utterance. Planning strategies are influenced by whether or not the speaker and hearer mutually believe appropriate facts about the intended referent. In particular, if the speaker and hearer share enough knowledge about the descriptions denotation and the contextual situation, it may be possible for the hearer to recognize the speakers intenrt,~as using only a subset of the descriptors in the n~mn phrase's description. In such a situation, the speaker ran augment the description with additional descriptors for tile purpose of informing the hearer that they are true ,ff the denotation of the other part of the description. Such a ~trate~' is called action anbaurnption, {Appeit, i985). The action subsumption strategy cannot be used with concept activation actions that are not based on shared knowledge.</Paragraph>
      <Paragraph position="4"> Since there are two dimensions relevant to ,:haracterizing concept activation actions, it is possible to define four  Ide~t * r ,cat *an Intent*on NS! Tyuw oi r nov ohrDl~ * i * efgc~t*a|, gttr ,bog, vq.</Paragraph>
      <Paragraph position="5"> dellm*te mtd *ndefi~|ta.</Paragraph>
      <Paragraph position="6"> PIM*I*S sir iles$~ * UNC.I d~.cr,ol*e* ~* * deer, ' *C/oC/**~ alan ~bsu~t e ** *ntemt **ns reCOSn*Sed **lv e#te~ no ~h~retl ,dm~t~f~C/~t*e* is caN|It* Tvae ef .e~ ~hrwses T~ ef noun DhrsSe~ Rif~mt*l|. ~w~l~irtntte. flttrtb~ttve, def*~ltt ~ * ndeftn~ to.</Paragraph>
      <Paragraph position="7"> p|m~t ,~1 str e|l~J~t P|m,~J st~et4~J~ e |afeC/lmt*ve ~r~Gt lea ~ff ~C/tm~t d~rscr * Og * NSNI 5NI s| fvae or noun O~r~e~ hr.=At,el, d*C/,~,tu ,nciud,*~ dGaenstret*ves.</Paragraph>
      <Paragraph position="8"> P I~n *n*J strmteSY* PSff,cie~t ,dent,rv,ng dncrl:s*~ ~bsweot, ** bess* hie ~ed  actions, as illustrated in Figure 1. These actions are SI (shared concept activation with identification intention), NSI (nonshared concept activation with identification intention), SNI (shared concept activation with no identification intention), and NSNI (nonshared concept activation with no identification intention.) Each action has distinct preconditions, effects, and an assocated planning strategy.</Paragraph>
    </Section>
  </Section>
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