<?xml version="1.0" standalone="yes"?>
<Paper uid="C88-2162">
  <Title>Fahlman, S. E., NETL: A System for Representing and Using Real-World</Title>
  <Section position="3" start_page="796" end_page="796" type="metho">
    <SectionTitle>
2. TIlE LEXICAL HIERARCHY FOR COMMUNICATION
ACTS
</SectionTitle>
    <Paragraph position="0"> Consider DHPL's lexical hierarchy for communication acts \[KiparskyT1\]. This is a hierarchy by generality where specific instances reside at file bottom, and general grammar rules reside at the top. Given this hierarchy, which turns out to be incomplete, RINA is capable of coping with a missing specific phrases by inheriting form general categories.</Paragraph>
    <Paragraph position="2"> Each node in this hierarchy, denoted for reference purposes by a mnemonic word, is actually a full-fledged lexical phrase-an association of a syntactic pattern with its conceptual meaning.</Paragraph>
    <Section position="1" start_page="796" end_page="796" type="sub_section">
      <SectionTitle>
2.1 Specific Phrasal Entries: Two entries for ASK (PI and
</SectionTitle>
      <Paragraph position="0"> P2) Consider the representation of the word ask as it appears in the sentence below: (1) The meeting was long and tedious.  So Frank asked to leave early. pattern: X:person ask:verb Z:act concept:X communicated that act Z by X can achieve a goal G of X.</Paragraph>
      <Paragraph position="1"> The word ask is given in the lexicon as an entire phrase, or a pattern-concept pair \[Wilensky81\]. The abbreviated.notation for P1 above stands for a full-fledged frame \[Mueller84\] as shown below: (pattern (subject (instance X)) (verb (root ask) (comp (concept Z)) (concept (mtrans (actor X) (object (plan Z) (achieve (goal-of X))))) The pattern of the phrase has three constituents: a subject X (Frank), the verb itself, and a complement Z (to leave early). In particular, the semantics of the phrase specify that X is the sub-ject of the embedded act Z, a fact which is not explicit in the text. However, this specification fails in capturing further sentences, such as the following one.</Paragraph>
      <Paragraph position="2"> (2) Frank asked the chairman to adjourn the meeting. There are two discrepancies: (a) this sentence includes a direct object (the chairman), and (b) Frank is not the subject of the complement as prescribed in phrase Pl. Thus, a second phrase P2 is added on to account for sentences of this kind.</Paragraph>
      <Paragraph position="3"> pattern: X:person ask:verb Y:person Z:act concept:X communicated to Y that act Z by Y can achieve goal G of X However, in order to cope with lexical unknowns, common properties shared by such phrases must be extracted and generalized.</Paragraph>
    </Section>
    <Section position="2" start_page="796" end_page="796" type="sub_section">
      <SectionTitle>
2.2 Generalized Features
</SectionTitle>
      <Paragraph position="0"> The phrases PI and P2 above can be abstracted in three ways: (a) along semantics of general equi rules, (b) along the semantics of the word ask, and (e), along semantics of general eommuniea*tion verbs. When an unknown word is encountered, its behavior is derived from these general categories.</Paragraph>
      <Paragraph position="1"> (a) The general entry for ASK (P3): The semantic properties of ask itself can be generalized through the follwing phrase: pattern: X:person ask!verb Z:aet concept: X communicate that act Z can achieve a goal G of X This generalized phrase simply states the meaning of ask, namely &amp;quot;X communicates that act Z can achieve a goal of X&amp;quot;, regardless of ~) whoJi~ the object of the communication act, and (b) who egeeuteS the act Z.</Paragraph>
      <Paragraph position="2"> (b) The general EQUI-rule (P4 and PS): Semantic properties can be generalized across complement-taking verbs: pattern: X:person V:verb Z:act concept: X is the subject of the embedded act Z pattern: X:person V:verb Y:person Z:aet concept: Y is the subject of the embedded act Z These phrases dictate the default identity of the implicit subject in complement-taking verbs: it is either the object, or the subject (if an object does not exist) of the embedding phrase.</Paragraph>
      <Paragraph position="3"> (c) The general COMMUNICATION act (P6): Semantic features of communication acts can be further abstracted.</Paragraph>
      <Paragraph position="4"> pattern: X:person V:verb Y:person Z:infinitive-aet concept: Y communicated Z to Y Phrase P6 implies that (1) X communicated an act Z to Y, and (2) Z is a hypothetical act. When a new word is encountered, for which no specific phrase can be indexed in the lexicon, a hypothesis is constructed by inheriting general features from these general phrases.</Paragraph>
    </Section>
  </Section>
  <Section position="4" start_page="796" end_page="798" type="metho">
    <SectionTitle>
3. PHRASE INTERACTION
</SectionTitle>
    <Paragraph position="0"> How does the lexicon become operational in processing text? Consider the following three sentences, ordered according to their complexity.</Paragraph>
    <Paragraph position="1">  (1) Frank came over.</Paragraph>
    <Paragraph position="2"> (2) Frank asked Corinne to come over. (3) Frank plended Corinne to come over. (1) Sentence (1) is analyzed by simple table lookup. A phrase (PT-come over)is found in the lexicon, and its concept is instantiated. null (2) No single lexical phrase matches sentence (2). Therefore, the analysis of (2) involves interaction of two lexical phrases (P2-ask and P7-come over).</Paragraph>
    <Paragraph position="3"> (3) No specific lexical phrase matches (3), since it includes an unknown word. Therefore the analysis of (3) requires the use of generalized phrases, as elaborated below.</Paragraph>
    <Section position="1" start_page="798" end_page="798" type="sub_section">
      <SectionTitle>
3.1 Uniih~tion with a General Phrase
</SectionTitle>
      <Paragraph position="0"> No specific phrase in the lexicon matches the word plcod, but a hypothesis regarding the new word can be inherited from general phrases. What general phrase should be used? In our algorithm \[Zernik88\], properties are inherited from the #nost specific phrase which matches file input clause. In the case of plend above, properties are inherited from two generalized phrases P5-communicate and P6-,objeet-equi, as shown in the figure below: ward (to a native speaker), they certainly convey the main concepts, and a user becomes acknowledged of the model's state of knowledge. The general principle of operation is summarized  While, a single concept was constructed for the word ask in the previous example, for plend there are multiple possiblities to consider. Steps (2) and (3) are carried out for each.</Paragraph>
      <Paragraph position="1">  (1) Select in the hierarchy all possible categories (general  phrases) which match the unknown word. The communication act (P6) is one possible category for plead. (2) Unify the appropriate phrases. The general phrase P6communicate leaves some parameters unsp~ified. In par~ ticular, the identity of the subject of the embedded phrase is yet unknown-who is supposed to come over to whom? This missing argument is derived by unification with phrase P5, which dictates the default object-equi: the listener is supposed to come over to the speaker.</Paragraph>
      <Paragraph position="2"> (3) lnstantiate the constructed hypotheses: F.13 communicated to C.17 that C.17 will come over to F.13, where coming over achieves a goal of C.17.</Paragraph>
      <Paragraph position="3"> Several such hypotheses are instantiated.</Paragraph>
      <Paragraph position="4"> (4) Discriminate among the mnltiple hypotheses by their semautic ingredients. For example the preceding context suggests that Corinne's goal (and not Frank's goal) is active. This feature discriminates between two acts such as promise and plead.</Paragraph>
    </Section>
  </Section>
class="xml-element"></Paper>