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<Paper uid="J91-1003">
  <Title>met*: A Method for Discriminating Metonymy and Metaphor by Computer</Title>
  <Section position="2" start_page="0" end_page="55" type="abstr">
    <SectionTitle>
1. Introduction
</SectionTitle>
    <Paragraph position="0"> Metaphor and metonymy are kinds of figurative language or tropes. Other tropes include simile, irony, understatement (litotes), and overstatement (hyperbole).</Paragraph>
    <Paragraph position="1"> Example 1 &amp;quot;My car drinks gasoline&amp;quot; (Wilks 1978, p. 199).</Paragraph>
    <Paragraph position="2"> Example 2 &amp;quot;The ham sandwich is waiting for his check&amp;quot; (Lakoff and Johnson 1980, p. 35). Sentences (1) and (2) contain examples of metaphor and metonymy respectively. Neither sentence is literally true: cars do not literally drink nor do ham sandwiches literally wait. Notice, though, that the two sentences are interpreted differently. &amp;quot;My car&amp;quot; in (1) is commonly understood as resembling an animate drinker while in (2) &amp;quot;the ham sandwich&amp;quot; is generally interpreted as referring to the person who ordered the ham sandwich.</Paragraph>
    <Paragraph position="3"> Most of the considerable literature on metaphor and the smaller one on metonymy (see Van Noppen, De Knop and Jongen 1985; Shibles 1971) is from philosophy, linguistics, and psychology. On the whole, the two phenomena remain vague, poorly defined notions in that literature. In artificial intelligence (AI), detailed treatments of either metaphor or metonymy are relatively scarce. Moreover, most of those treatments are paper implementations that have not been coded up and run on a computer.</Paragraph>
    <Paragraph position="4"> * Centre for Systems Science, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6 (~) 1991 Association for Computational Linguistics Computational Linguistics Volume 17, Number 1 The met* (pronounced &amp;quot;met star'0 method provides a means for recognizing selected examples of metonymy and metaphor, and also anomaly and literalness, in short English sentences. 1 The method is part of Collative Semantics (hereafter CS), which is a semantics for natural language processing. CS, and hence the met* method, has been implemented in a program called meta5 (so called because it does more than metaphor). The meta5 program is, as far as I know, the first system to recognize examples of metaphor and metonymy. TO my knowledge, there is only one other working program that might be said to recognize instances of metaphor (Martin 1988; 1990) and two systems that appear to recognize cases of metonymy, TEAM (Grosz et al.</Paragraph>
    <Paragraph position="5"> 1987) and TACITUS (Hobbs and Martin 1987).</Paragraph>
    <Paragraph position="6"> The rest of the paper is organized as follows. Section 2 surveys general issues and approaches in metaphor and metonymy, notably the distinctive characteristics of metaphor and metonymy, the relationship between metaphor and metonymy, and the relationship between literalness and nonliteralness. Section 3 presents the met* method, concentrating on the basic topology of the met* method algorithm. Section 4 shows details of representations and processes used in CS. Section 5 gives examples of the meta5 program analyzing simple metaphors and metonymies. Descriptions get progressively more detailed from Section 2 through to Section 5. Sections 6 and 7 describe some extensions to metaphor interpretation in CS and compare the met* method against other approaches to metaphor and metonymy, especially computational ones.</Paragraph>
    <Paragraph position="7"> A glossary of key terms is provided at the very end of the paper.</Paragraph>
    <Paragraph position="8"> 2. Survey of Metonymy and Metaphor Research Metonymy and metaphor are so poorly understood that widely divergent views exist about them and their relationship to each other. This section reviews research on metaphor (2.1), metonymy (2.2), the relationship between them (2.3), and the more general relationship between literalness and nonliteralness (2.4).</Paragraph>
    <Section position="1" start_page="0" end_page="50" type="sub_section">
      <SectionTitle>
2.1 Metaphor
</SectionTitle>
      <Paragraph position="0"> Four views of metaphor are critically discussed: the comparison view, the interactive view, the selection restriction violation view, and the conventional metaphor view.</Paragraph>
      <Paragraph position="1"> Computational examples of each kind are included by Gentner, Indurkhya, Hobbs, Wilks, and Martin. Space does not permit discussion of other AI work on metaphor by, e.g., Russell (1976) and Weiner (1984; 1985).</Paragraph>
      <Paragraph position="2">  a metaphor is a comparison in which one term (the tenor or subject of the comparison) is asserted to bear a partial resemblance (the ground of the comparison) to something else (the vehicle), the resemblance being insufficient to sustain a literal comparison. As with any comparison, there is always some residual dissimilarity (the tension) between the terms involved in the comparison, but comparison theorists tend not to emphasize this dissimilarity (Tourangeau and Sternberg 1982, p. 205, their italics).</Paragraph>
      <Paragraph position="3"> What is crucial in the comparison approach, then, is finding the correct ground in a metaphor. According to Tourangeau and Sternberg, Aristotle proposed the first  collectively to metonymy and metaphor: &amp;quot;*&amp;quot; is a match-anything symbol in the Unix operating system; hence, the token &amp;quot;met*&amp;quot; matches the two tokens &amp;quot;metonymy&amp;quot; and &amp;quot;metaphor.&amp;quot;</Paragraph>
    </Section>
    <Section position="2" start_page="50" end_page="52" type="sub_section">
      <SectionTitle>
Fass Discriminating Metonymy
</SectionTitle>
      <Paragraph position="0"> comparison theory and suggested several principles for finding the ground of a metaphor.</Paragraph>
      <Paragraph position="1"> Tourangeau and Sternberg reduce these principles to two basic ones: finding a category to which the tenor and vehicle belong and constructing an analogy involving them.</Paragraph>
      <Paragraph position="2"> Gentner's (1983) Structure-Mapping Theory, which has been implemented in the Structure-Mapping Engine (Falkenhainer, Forbus and Gentner 1989), closely resembles a comparison view of metaphor. The theory addresses literal similarity, analogy, abstraction, and anomaly, which Gentner refers to as four &amp;quot;kinds of comparison.&amp;quot; An algorithm compares the semantic information from two concepts represented as sets of properties. Properties are either &amp;quot;attributes,&amp;quot; one-place predicates like LARGE(x), or &amp;quot;relations,&amp;quot; two-place predicates such as COLLIDE(x,y). The four kinds of comparison are distinguished by the relative proportions of attributes and relations that are matched, and the forms of mappings established between them. Mappings between relations are sought before those between attributes. Pairs of relations are compared using the &amp;quot;systematicity principle&amp;quot; that regular structural correspondences should exist between terms occupying the same positions in those relations. Mappings are purely structural and independent of the content of the relations (i.e., the predicates).</Paragraph>
      <Paragraph position="3"> Tourangeau and Sternberg (1982) list some problems with the comparison view, including the following: (a) that everything has some feature or category that it shares with everything else, but we cannot combine just any two things in metaphor; (b) that the most obvious shared features are often irrelevant to a reading of the metaphor; (c) that even when the feature is relevant, it is often shared only metaphorically; ... and (e) that metaphors are novel and surprising is hard to reconcile with the idea that they rely completely on extant similarities (ibid., pp. 226-227).</Paragraph>
      <Paragraph position="4"> Johnson (1980) also notes problem (a) with comparison theories, pointing out that as a result they cannot account for the semantic tension between the two terms of a metaphor: the comparison theory ... tries to circumvent the experienced semantic strain by interpreting metaphor as nothing but a way of comparing two things to see in what respects they are alike. And since any two things are similar in some respects, this kind of theory can never explain what is interesting and important about metaphor (ibid., p. 52).</Paragraph>
      <Paragraph position="5">  novelty that metaphors create. According to Tourangeau and Sternberg (1982, p. 212), proponents of the interaction view include Black (1962), Hesse (1966), Miles (1967), Richards (1936), and Wheelwright (1962).</Paragraph>
      <Paragraph position="6"> Interaction theorists argue that the vehicle of a metaphor is a template for seeing the tenor in a new way. This reorganization of the tenor is necessary, because the characteristics or features of the vehicle cannot be applied directly to the tenor; the features they 'share' are often only shared metaphorically. As Black (1962) observes, the ground of a metaphor may itself be nonliteral. 'Men are wolves,' in Black's example, in part because both are predators; but they are predators in sharply different senses that may only strike us as similar when we interpret the metaphor. In Black's reading of this metaphor, we see competition in social relations as corresponding to predacity in beasts (Tourangeau and Sternberg 1982, pp. 212-213).</Paragraph>
      <Paragraph position="7">  Computational Linguistics Volume 17, Number 1 A problem with the interaction view is that theorists have not provided much detail about the processes involved, though Black (1962) does make some suggestions. According to Black, tenor and vehicle.., each have a 'system of commonplaces' associated with them. These commonplaces are stereotypes, not necessarily definitional, not even necessarily true, just widely agreed upon. In interpreting 'man is a wolf,' we 'evoke the wolf-system of related commonplaces' and are led by them 'to construct a corresponding system of implications about the principal subject (Man)' (Black, 1962, p. 41). In Black's view, then, interpretation involves not so much comparing tenor and vehicle for existing similarities, as construing them in a new way so as to create similarity between them (Tourangeau and Sternberg 1982, p. 213).</Paragraph>
      <Paragraph position="8"> One might distinguish, then, two main differences between the interaction and comparison views. First, similarities are &amp;quot;created&amp;quot; in the interaction view (accounting for the novelty and surprise in a metaphor) whereas only pre-existing similarities are found in the comparison view. Second, a whole system of similarities are evoked between tenor and vehicle in the interactions view, whereas the comparisons view is based upon finding a single similarity.</Paragraph>
      <Paragraph position="9"> One version of the interaction view is the domains-interaction view, set forth by Tourangeau and Sternberg (1982), who take the view that features 'shared' by tenor and vehicle are often at best only analogous features, each limited in its application to one domain or another. Of course, some features or dimensions are quite general, applying across the board to a number of domains (p. 218).</Paragraph>
      <Paragraph position="10"> Among comparison and interaction theorists, much attention had been paid to selecting the comparisons or interactions in a metaphor. The importance of analogy or correspondence in metaphor has been stressed by Gentner (1983), Ortony (1979), Tourangeau and Sternberg (1982), and Wilks (1978), among others. Various mechanisms have been advanced for highlighting certain comparisons or interactions, including relevance (e.g., Hobbs 1983b; Tversky 1977) and salience (Ortony et al. 1985). Among computational approaches, Indurkhya's (1988) Constrained Semantic Transference theory of metaphor can be viewed as a formalization of Black's interaction theory (ibid., p. 129). Source and target domains are viewed as &amp;quot;systems of relationships.&amp;quot; In metaphorical interpretation, an &amp;quot;implicative complex&amp;quot; of the source domain is imposed on the target domain, thereby shaping the features of the target domain, which in turn produces changes in the features of the source domain, hence the &amp;quot;interaction.&amp;quot; It is assumed that a structural analogy underlies every metaphor (ibid., p. 129).</Paragraph>
      <Paragraph position="11"> A metaphor is identified with the formal notion of a T-MAP which is a pair / F,S / where F is a function that maps vocabulary of the source domain onto vocabulary of the target domain and S is a set of sentences from the source domain which are expected to transfer to the target domain. A metaphor is &amp;quot;coherent&amp;quot; if the transferred sentences S are logically consistent with the axioms of the target domain, and &amp;quot;strongly coherent&amp;quot; if they already lie in the deductive closure of those axioms (cf. Stallard 1987, p. 181). S is thus the &amp;quot;implicative complex&amp;quot; of the source domain imposed on the target domain. Every metaphorical interpretation of a given set of sentences is associated with a T-MAP. There may be several possible T-MAPs for a set of sentences.</Paragraph>
      <Paragraph position="12"> I would argue that Hobbs (1983a; 1983b) has also taken an interaction view of metaphor. Hobbs' goal has been to develop a unified process of discourse interpretation based on the drawing of appropriate inferences from a large knowledge base,</Paragraph>
    </Section>
    <Section position="3" start_page="52" end_page="54" type="sub_section">
      <SectionTitle>
Fass Discriminating Metonymy
</SectionTitle>
      <Paragraph position="0"> which Hobbs sometimes calls &amp;quot;selective inferencing&amp;quot; (e.g., Hobbs 1980). Selective inferencing is concerned with drawing or refraining from drawing certain inferences in a controlled fashion (cf. Hobbs 1983a). He argues that many problems have the same or almost the same inferencing solutions. These solutions are found via four separate semantic operations that all draw inferences from text (e.g., Hobbs 1977).</Paragraph>
      <Paragraph position="1">  view has also been called &amp;quot;the semantic deviance view&amp;quot; (Johnson 1980, p. 50) and &amp;quot;the anomaly view&amp;quot; (Tourangeau and Sternberg 1982, p. 211). Johnson (1980) describes this view as a common one among linguists; Tourangeau and Sternberg (1982) list the following people as holders of this view: Beardsley (1962), Bickerton (1969), Campbell (1975), Guenther (1975), Percy (1954), Van Dijk (1975), and Wheelwright (1962). To this list one might add Levin (1977). Johnson (1980, p. 50) describes this view as where: metaphor constitutes a violation of selection restriction rules within a given context, where the fact of this violation is supposed to explain the semantic tension one experiences in comprehending any live metaphor.</Paragraph>
      <Paragraph position="2"> The theory of metaphor in Preference Semantics (Wilks 1975; 1978) consists of a selection restrictions view and a comparison view. In the theory, information about word senses is contained in knowledge structures called &amp;quot;semantic formulas.&amp;quot; An algorithm matches pairs of semantic formulas, seeking satisfied or violated preferences between them. A satisfied preference indicates a literal semantic relation; a violated preference indicates either a metaphorical or anomalous one. This part of the theory is implemented in a machine translation system (Wilks 1973).</Paragraph>
      <Paragraph position="3"> To distinguish metaphor from anomaly, a different knowledge structure and a second algorithm are used. The algorithm, called projection, operates on a knowledge structure, called a pseudo-text, that contains lists of templates (a further kind of knowledge structure) linked by case ties. A brief example of projection is given for (1). Example 3 &amp;quot;My car drinks gasoline.&amp;quot; Projection operates only on preference violations. The best representation of (1) contains a preference violation, so projection is used. The algorithm compares the template representation for the sentence \[my+car drink gasoline\] against templates from the pseudo-text of 'car' seeking &amp;quot;the closest match,&amp;quot; and selects \[ICengine (USE)#1iquid\]. (USE) is projected onto drink in the sentence representation  &amp;quot;No man is an Island&amp;quot; (John Donne, Meditations XVII).</Paragraph>
      <Paragraph position="4"> The main problem with the selection restrictions view is that perfectly well-formed sentences exist that have a metaphorical interpretation and yet contain no selection restriction violations (Johnson 1980; Ortony 1980; Reddy 1969); for example, in (3), there is a literal interpretation when uttered about a stone and a metaphorical one when said about a decrepit professor emeritus. Sentences (4), (5) and (6) also have twin interpretations.</Paragraph>
      <Paragraph position="5"> The existence of such sentences suggests that a condition that occasionally holds (i.e., a selection restriction violation) has been elevated into a necessary condition of metaphor (Johnson 1980). Moreover, viewing metaphor only in terms of selection restriction violations ignores the influence of context: We seem to interpret an utterance metaphorically when to do so makes sense of more aspects of the total context than if the sentence is read literally. Consider the simple case of the sentence All men are animals as uttered by Professor X to an introductory biology class and as uttered later by one of his female students to her roommate upon returning from a date. In the latter instance the roommate understands the utterance as metaphorical (ibid., p. 51).</Paragraph>
      <Paragraph position="6"> In a similar way, Ortony (1980) suggests that metaphor should be thought of as contextually anomalous. This means that a literal interpretation of the expression, be it a word, phrase, sentence, or an even larger unit of text, fails to fit the context (p. 73, his italics), so whether or not a sentence is a metaphor depends upon the context in which it is used: if something is a metaphor then it will be contextually anomalous if interpreted literally .... Insofar as the violation of selection restrictions can be interpreted in terms of semantic incompatibilities at the lexical level, such violations may sometimes be the basis of the contextual anomaly (ibid., p. 74).</Paragraph>
      <Paragraph position="7">  ized the idea of conventional metaphors, also known as conceptual metaphors. They distinguish three main kinds: orientational, ontological, and structural. Orientational metaphors are mainly to do with kinds of spatial orientation like up-down, in-out, and deep-shallow. Example metaphors include MORE IS UP and HAPPY IS UP. They arise from human experience of spatial orientation and thus develop from the sort of bodies we have and the way they function in our physical environment.</Paragraph>
      <Paragraph position="8"> Ontological metaphors arise from our basic human experiences with substances and physical objects (especially our own bodies). Some examples are TIME IS A SUB-STANCE, THE MIND IS AN ENTITY, and THE VISUAL FIELD IS A CONTAINER.</Paragraph>
    </Section>
    <Section position="4" start_page="54" end_page="54" type="sub_section">
      <SectionTitle>
Fass Discriminating Metonymy
</SectionTitle>
      <Paragraph position="0"> Structural metaphors are elaborated orientational and ontological metaphors (cf.</Paragraph>
      <Paragraph position="1"> Lakoff and Johnson 1980) in which concepts that correspond to natural kinds of experience, e.g., PHYSICAL ORIENTATIONS, SUBSTANCES, WAR, JOURNEYS, and BUILDINGS, are used to define other concepts, also natural kinds of experience, e.g., LOVE, TIME, IDEAS, UNDERSTANDING, and ARGUMENTS. Some examples of structural metaphors are ARGUMENT IS WAR and TIME IS MONEY.</Paragraph>
      <Paragraph position="2"> The ARGUMENT IS WAR metaphor forms a systematic way of talking about the battling aspects of arguing .... Because the metaphorical concept is systematic, the language we use to talk about the concept is systematic (ibid., p. 5).</Paragraph>
      <Paragraph position="3"> What Lakoff and Johnson fail to discuss is how metaphors in general, let alone individual metaphorical concepts, are recognized. Martin's (1988; 1990) work has addressed this issue. He has pursued a conventional metaphor view using KODIAK (Wilensky 1984), a variant of Brachman's KLONE knowledge representation language.</Paragraph>
      <Paragraph position="4"> Within KODIAK, metaphorical relationships are represented using a primitive link type called a &amp;quot;VIEW.&amp;quot; A VIEW &amp;quot;is used to assert that.., one concept may in certain circumstances be considered as another &amp;quot; (Martin 1990, p. 59). In Martin's work, &amp;quot;metaphor-maps,&amp;quot; a kind of VIEW (ibid., p. 64), are used to represent conventional metaphors and the conceptual information they contain.</Paragraph>
    </Section>
    <Section position="5" start_page="54" end_page="54" type="sub_section">
      <SectionTitle>
2.2 Metonymy
</SectionTitle>
      <Paragraph position="0"> Metonymy involves &amp;quot;using one entity to refer to another that is related to it&amp;quot; (Lakoff and Johnson 1980, p. 35).</Paragraph>
      <Paragraph position="1"> Example 2 &amp;quot;The ham sandwich is waiting for his check.&amp;quot; For example, in (2) the metonymy is that the concept for ham sandwich is related to an aspect of another concept, for &amp;quot;the person who ordered the ham sandwich.&amp;quot; Several attempts have been made to organize instances of metonymy into categories (e.g., Lakoff and Johnson 1980; Stern 1931; Yamanashi 1987) or &amp;quot;metonymic concepts,&amp;quot; as Lakoff and Johnson call them. A common metonymic concept is PART FOR WHOLE, otherwise known as synechdoche.</Paragraph>
    </Section>
    <Section position="6" start_page="54" end_page="55" type="sub_section">
      <SectionTitle>
Example 7
</SectionTitle>
      <Paragraph position="0"> &amp;quot;Dave drank the glasses&amp;quot; (= the liquid in the glasses).</Paragraph>
      <Paragraph position="1"> Example 8 &amp;quot;The kettle is boiling&amp;quot; (= the liquid in the kettle) (Waldron 1967, p. 186; Yamanashi 1987, p. 78).</Paragraph>
      <Paragraph position="2"> CONTAINER FOR CONTENTS, another metonymic concept, occurs in (7) between 'drink' and the sense of 'glasses' meaning &amp;quot;containers,&amp;quot; and also in (8). In (7), 'drink' has an object preference for a potable liquid, but there is a preference violation because glasses are not potable liquids. It is not glasses that are drunk, but the potable liquids in them. There is a relationship here between a CONTAINER (a glass) and its typical CONTENTS (a liquid): this relationship is the metonymic concept CONTAINER FOR  Computational Linguistics Volume 17, Number 1 CONTENTS. Below are examples of two further metonymic concepts (from Lakoff and Johnson 1980, p. 38, italics in original).</Paragraph>
    </Section>
  </Section>
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