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<Paper uid="W03-1404">
  <Title>Systematicity and the Lexicon in Creative Metaphor</Title>
  <Section position="2" start_page="0" end_page="0" type="intro">
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1 Introduction
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    <Paragraph position="0"> When one considers the aptness of creative metaphor and how one might measure it, one finds a whole range of issues lurking between the apparent unity of this umbrella term. This complexity is compounded by the fact that metaphors operate at several different levels of representation simultaneously: the conceptual level, or the level of ideas; the lexical level, or the level of words; and the pragmatic level, or the level of intentions. A metaphor may fall at any of these hurdles, either through a poor choice of a source concept, a poor choice of words in communicating this concept, or in a failure to observe the expectations of the context in which the metaphor is expressed.</Paragraph>
    <Paragraph position="1"> Some degree of aptness is afforded by metaphors that compare semantic neighbors, inasmuch as the existence of a common taxonomic parent suggests that the source and target are in the same, or at least similar, domains (e.g., see Way, 1991). For instance, metaphors that compare politicians to architects, or even geneticists to cartographers, derive some measure of aptness from the fact that in each case the source and target are sub-categories of the Profession category.</Paragraph>
    <Paragraph position="2"> However, since the most creative of metaphors are those that make the greatest semantic leaps between the source and target concepts, such category-hopping metaphors do not have the luxury of comparing concepts that are already deemed similar in taxonomic terms, as evidenced by a common superordinate concept, but must instead establish a new basis for conveying similarity that is not itself taxonomic. Consider for instance a corollary of the above metaphor in which &amp;quot; genomes are maps&amp;quot; . The aptness of these similarity-creating metaphors is instead a measure of the isomorphism between the relational structures of the source and target, so that the concepts with the greatest structural overlap will often produce the most apt metaphors. In this respect, metaphoric aptness is a function of what Gentner terms the systematicity of a structuremapping. According to (Gentner, 1983) and the structure-mapping school of thought (e.g., see also Veale and Keane, 1997), the best interpretations of a metaphor or analogy are those that systematically pair-off the greatest amount of connected relational structure in each concept. We refer to this kind of structural aptness as internal systematicity, since any sense of aptness arises out of a coherence between the internal structures of the concepts being mapped.</Paragraph>
    <Paragraph position="3"> Lakoff and Johnson (1980) also place a strong emphasis on metaphoric systematicity, but in their hands the notion is construed in more external terms. To L&amp;J, systematicity is a measure of the generativity of a metaphoric schema, so that the same schema (such as Life is a Journey) can serve as the deep structure for a wide variety of different, but mutually systematic, surface metaphors (such as &amp;quot; my job has hit a rocky patch&amp;quot; and &amp;quot; my career has stalled&amp;quot; ). In this view, systematicity is a measure of how much a metaphor resonates and coheres with existing metaphors for thinking about the target concept, so that when viewed collectively, they together suggest the operation of a common underlying schema. This view of systematicity is external to the concepts involved since it predicates their aptness to each other on the existence of other structures (metaphor schemas) into which they can be coherently connected.</Paragraph>
    <Paragraph position="4"> In this paper we argue that the lexicon is central to the determination of both kinds of systematicity, internal and external, especially if one is an adherent of the generative lexicon view of word meaning as championed by (Pustejovsky, 1991). In such a lexicon we can expect to find precisely the kind of relational structure needed to perform structure mapping and thereby measure the internal systematicity of a metaphor like &amp;quot; a passport is a travel diary&amp;quot; . In addition, we can expect to find the lexicalized metaphor structures that represent the surface manifestations of existing modes of thought, and it is against these structures that the external systematicity of an interpretation can be measured.</Paragraph>
    <Paragraph position="5"> This research is conducted in the context of WordNet (Miller, 1995; Fellbaum, 1998), a comprehensive lexical knowledge-base of English.</Paragraph>
    <Paragraph position="6"> The structure of WordNet makes explicit some of the relationships needed to construct a generative lexicon, most obviously the formal (taxonomic) and constitutive (meronymic) aspects of word meaning. But to truly test a model of metaphoric interpretation on a large-scale, it is necessary to augment these relationships with the telic and agentive components that are not encoded directly but merely alluded to in the textual glosses associated with each sense entry. In the sections to follow we describe a mechanism for automating the extraction of these relationships (in the same vein as (Harabagiu et al. 1999), and for using them to generative apt interpretations for metaphors involving WordNet entries.</Paragraph>
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