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  <Title>A Knowledge Representation Approach to Understanding Metaphors</Title>
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3 Conklin and McDonald (1982) have used salience as a means
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    <Paragraph position="0"> of solving the selection problem in natural language generation using KL-ONE as the representation language.</Paragraph>
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2 Computational Linguistics, Volume 10, Number 1, January-March 1984
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    <Paragraph position="0"> E. Judith Weiner A Knowledge Representation Approach to Understanding Metaphors Figure I.</Paragraph>
    <Paragraph position="1"> would probably mean to most people that Mary's cheeks are round and red. A different interpretation would be obtained if the concept of round, red apple were replaced by a withered, rotten one or even, for that matter, by a green one. For communication to take place among people in a speech community, some sort of prototypicality considerations are essential.</Paragraph>
    <Paragraph position="2"> There is another way in which prototypicality might figure in a discussion of metaphors. It seems probable  that the B term in (1) A is like B represents the epitome of the predicate(s) that are true of A and of interest in a given utterance, that is, B is the prototypical representative of these predicates. (Tversky (1977) observed that the B term is the more prototypical of the two in literal sentences.) If the sentence reverses A and B, then A becomes the prototype of (probably) different predicates. The vehicle of choice should be one in which the cluster of predicates is (ideally) uniquely appropriate, prototypical, and therefore also salient. For example, (5) A hose is like a snake  Snakes are typically, even classically, the ultimate in long, narrow, coiledness; these characteristics can be thought of as distinguishing snakes from other members of the category ANIMALS. Sentence (5) draws the reader's attention to these (perhaps) slightly less salient qualities of a hose.</Paragraph>
    <Paragraph position="3"> I have intentionally limited myself to sentences taken out of the discourse context. One of the benefits of doing this is that there is considerable context within the sentence itself that can influence its interpretation. Consider the following pair of sentences  (6) My cat's tail is like a carrot (7) John's hair is like a carrot  Without adding any context, it is unlikely that a per-son would miss the fact that the relevant salient predicate of (6) is shape (and perhaps color) and that of (7) is color. Our knowledge of prototypical cats with prototypical cat tail shapes and colors and prototypical hair shapes and colors leads us to the right conclusion. If no additional information is available, then it wouldn't be likely that John was wearing a pony tail. On the other hand  (8) John's nose is like a carrot again, taken out of context, would indicate a comment about shape. From these examples it should be clear that prototypicality considerations are relevant to both topic and vehicle.</Paragraph>
    <Paragraph position="4"> 5. Prototypicality and Possibility  How then, does this relate to prototype theory? The relationship appears to be that, in the prototypical tail, nose, or hair, certain predicates are probable. These are the ones most likely to match those salient in B. Thus in order to process metaphors, it is necessary to know, in addition to the nature of the prototype, a range of probable values for a given predicate. This would facilitate Ortony's determination (1979a, p. 173) of &amp;quot;whether any gross incompatibility would result by applying the predicate in question to the Computational Linguistics, Volume 10, Number 1, January-March 1984 3 E. Judith Weiner A Knowledge Representation Approach to Understanding Metaphors concept.&amp;quot; This range can help determine whether the statement is literally true or not. For example, (9) John's hands are like ice.</Paragraph>
    <Paragraph position="5"> If a range of possible temperatures were built into the representation for human hands, it would be known that John's hands could not possibly be literally as cold as ice (there could not be an actual equivalence of temperature in hands and in ice). 4 The figurative interpretation would thus prevail.</Paragraph>
    <Paragraph position="6"> Prototypicality and range of possible values appear to operate throughout language as a whole; they are not confined to figurative usage. Labov (1973) reported on an experiment on the denotation of the word cup. He gave subjects pictures of cuplike objects to identify and observed differing percentages of the use of cup as form and function were varied. He concluded the existence of an invariant core (corresponding to my use of prototype) as well as a range of deviations through which recognition still occurred, albeit at lower percentages. The inclusion of these elements in the knowledge representation of a system for understanding natural language is therefore broadly motivated.</Paragraph>
    <Paragraph position="7"> 6. Metaphors as Hyperboles All metaphors are hyperbolic in a sense. They seem to say: the predicates A shares with B are in A so extreme that they can only be expressed by relating them to some object in which they are epitomized, that is,  B. In (9) John's hands are like ice, the exaggeration is apparent. This is evident because of the range of possible temperature values known to be actually attributable to human hands. The sentence (7) John's hair is like a carrot.</Paragraph>
    <Paragraph position="8"> is less metaphoric (consequently more literal) in this sense. It is possible that hair could be the same color as the prototypical carrot, but the probability is low. Consequently, the following sequence does not seem absurd: (10) John's hair is like a carrot.</Paragraph>
    <Paragraph position="9"> Is it really that color? whereas (11) John's hands are like ice.</Paragraph>
    <Paragraph position="10">  Are they really that cold? would lead one to think the response peculiar at the least. On some scale of metaphoricity then, (10) is less metaphoric than (11). Since a hose may in fact be as long, narrow, coiled as a snake,  4 If John is assumed to be living and context does not indicate the possibility of frostbite conditions. (5) A hose is like a snake  is the least metaphoric of the examples given. This supports Ortony's claim that high salient predicates of A matched with high salient predicates of B make for a literal statement. A response of Is it really that long, narrow, coiled? could easily be followed by an unqualified response of &amp;quot;'Yes. '&amp;quot; Ortony (1975) denies the possibility of the ground consisting merely of a single predicate. &amp;quot;People simply do not use metaphors to transfer one characteristic, even if it is a distinctive one, when there is a ready literal way of making the point.&amp;quot; (p. 50.) Sentence (9), however, provides a fairly good counterexample to this claim. Here, the hyperbolic nature of the metaphor rather than the size of the ground provides the incentive for its use.</Paragraph>
    <Paragraph position="11"> 7. Taxonomic Structure and Incongruity The conclusion which should be drawn from this discussion is that all of the above factors must be brought to bear in an analysis of metaphor understanding. The result of using these measures will be an isolation of those predicates of B that are true of A and the establishment of a relative degree of metaphoricity within the sentence context.</Paragraph>
    <Paragraph position="12"> Given a corpus of sentences of the form  (1) A is (like) B, some will appear to be literal similarity statements; others will appear to be metaphors.</Paragraph>
    <Paragraph position="13"> (12) John is like his father.</Paragraph>
    <Paragraph position="14"> (13) John is like a snake.</Paragraph>
    <Paragraph position="15"> (14) John is like a black box.</Paragraph>
    <Paragraph position="16">  In (12), the sentence appears to be a literal comparison. John shares certain characteristics with his father. John and his father are already known to be similar on the basis of the fact that they are members of the same superordinate category (males) or are already known to participate in a relationship to one another (father-son). There is no element of surprise or incongruency in statement (12). As Ortony has proposed, high salient predicates of B are also high salient predicates of A. This is Ortony's criterion for a literal similarity statement as opposed to a metaphor. I think, however, that viewing this phenomenon from the perspective of category membership, relationship and consequent incongruity will shed more light on its computation representation.</Paragraph>
    <Paragraph position="17"> There do seem to be metaphorical statements in which there is matching of high salient predicates in both the vehicle and the topic. If sentence (8) John's nose is like a carrot were uttered by one of John's friends to another, it would not represent new information. It would proba-</Paragraph>
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