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<?xml version="1.0" standalone="yes"?> <Paper uid="J83-3004"> <Title>Preference Semantics, III-Formedness, and Metaphor</Title> <Section position="4" start_page="0" end_page="0" type="metho"> <SectionTitle> 2. Three Types of Dictionary Information </SectionTitle> <Paragraph position="0"> The semantic information in dictionary entries (formulas) can be categorised into three types, which will be exemplified in the semantic formula for drink (3).</Paragraph> <Paragraph position="1"> (i) Inherent information: &quot;data&quot; The semantic properties that a dictionary entry contains specifically about the item itself. In a semantic formula, the main example of this is its head primitive(s), for example (MOVE CAUSE).</Paragraph> <Paragraph position="2"> (ii) Label information: &quot;labels&quot; Case information describing the case relationships between a dictionary entry and other dictionary entries. Label information exists in the case subparts of semantic formulas as case primitives like SUBJ (to be interpreted as AGENT) in (*ANI SUBJ), and OBJE in</Paragraph> </Section> <Section position="5" start_page="0" end_page="0" type="metho"> <SectionTitle> ((FLOW STUFF) OBJE). </SectionTitle> <Paragraph position="0"> (iii) Contextual information: &quot;expectations&quot; The inherent semantic information that a dictionary entry expects other dictionary entries to possess as inherent information. Like label information, contextual information exists in the case subparts of semantic formulas as semantic primitives or subformulas like *ANI and (FLOW STUFF).</Paragraph> <Paragraph position="1"> When disambiguating word-senses, all three types of information are used. In section 1 above, we saw how the template expansion algorithm resolved (4): \[interrogate\] prefers a human object, where &quot;object&quot; is label information, and &quot;human&quot; is contextual information. \[crook (man)\] satisfies this preference because its head primitive - inherent information - is human.</Paragraph> <Paragraph position="2"> We wish to distinguish dictionary entries that contain semantic contextual information and those that do not: * predicates Contextual information occurs in the semantic formulas for verbs, adjectives, nominalised verbs, and idioms (Wilks 1975, Boguraev 1979).</Paragraph> <Paragraph position="3"> Dictionary entries for prepositions, called paraplates (Wilks 1975) or preplates (Boguraev 1979), larger structures that tie templates together and have the function of inference rules, also contain contextual information because they specify the semantic class of head noun or verb being modified and the head noun of modifying prepositional phrase, but they are outside the scope of discussion here.</Paragraph> <Paragraph position="4"> * non-predicates Simple nouns like table, car, and chopper, which do not contain contextual information in their semantic formulas at the top level (that is, \[car\] might contain coding that humans use cars to achieve a goal, but that would not appear at the top level of the &quot;goals of cars&quot;).</Paragraph> <Paragraph position="5"> By &quot;predicate&quot; we mean specifically dictionary entries containing semantic contextual information at the top level, and not the more general use of the term.</Paragraph> </Section> <Section position="6" start_page="0" end_page="0" type="metho"> <SectionTitle> 3. Two Types of &quot;Preference&quot; </SectionTitle> <Paragraph position="0"> This section examines the notion of preference and makes an important distinction between a declarative and a procedural version of preference (Fass 1983).</Paragraph> <Section position="1" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 3.1. Preference-as-restriction </SectionTitle> <Paragraph position="0"> A preference is (dictionary) information in a semantic formula expressing some kind of restriction on the semantic context in which a word-sense can occur.</Paragraph> <Paragraph position="1"> 180 American Journal of Computational Linguistics, Volume 9, Numbers 3-4, July-December 1983 Dan Fass and Yorick Wilks Preference Semantics, III-Formedness, and Metaphor Two observations: Preferences-as-restrictions are binary.</Paragraph> <Paragraph position="2"> A preference is either satisfied or violated: it cannot be partially satisfied. This is because of the organisation and generality of PS semantic primitives, which are hierarchically organised but only at two levels of generality. For example, the &quot;class element&quot; primitive *ANI includes the class of primitives (BEAST, MAN, FOLK, SIGN, or THIS), that is, any animate entity.</Paragraph> <Paragraph position="3"> There can be no partially satisfied preferences with the present set of primitives, as would be the case if BEAST could satisfy a preference for MAN because both are in the class *ANI.</Paragraph> <Paragraph position="4"> A preference is a piece of contextual information.</Paragraph> <Paragraph position="5"> Although a preference coding occurs within a case subpart of a formula, the corresponding label information is not part of that preference.</Paragraph> <Paragraph position="6"> As preferences-as-restrictions are contextual, it is only predicates that have them in PS. But if preferences-as-restrictions referred instead to inherent information, then non-predicates would also have preferences. Consider the helicopter meaning of the word chopper, whose formula has the head primitive THING (that is, physical object). If a preference described inherent information, then we could view choppers as preferring to be THINGs but not having to be THINGs.</Paragraph> <Paragraph position="7"> We shall consider just this in section 6.</Paragraph> </Section> <Section position="2" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 3.2. Preference-as-procedure </SectionTitle> <Paragraph position="0"> Preference is viewed as a procedure for assigning scores to competing alternative representations and choosing the best one. In PS, preference-as-procedure uses as its criterion for choosing between competing sentence readings the number of preferences-as-restrictions that are satisfied.</Paragraph> <Paragraph position="1"> The four key elements of preference-as-procedure are: * production - it produces all sentence readings whether or not they contain preference violations; null * scoring - readings are scored according to how many preference satisfactions they contain; * comparison - whether or not an individual reading is accepted depends on a comparison with other readings; * selection - the best reading (that is, the one with the most preference satisfactions) is taken, even if it contains preference violations.</Paragraph> <Paragraph position="2"> By choosing the best available, preference-as-procedure as a single procedure has two effects when it operates: it disambiguates word-senses and at the same time provides system robustness (that is, a sentence reading is always returned).</Paragraph> <Paragraph position="3"> It should be emphasised that preference-as-procedure is a general strategy, used to provide disambiguation and robustness at many different levels in the PS system, not just with preferences-asrestrictions. The two types of preference are separable from each other: preferences-as-restrictions can be used by other procedures, and preference-as-procedure can be used with other types of dictionary information. null</Paragraph> </Section> </Section> <Section position="7" start_page="0" end_page="0" type="metho"> <SectionTitle> 4. The Preference Semantics System and Ill- </SectionTitle> <Paragraph position="0"/> <Section position="1" start_page="0" end_page="0" type="sub_section"> <SectionTitle> Formed Input 4.1. Preference Semantics and ill-formedness </SectionTitle> <Paragraph position="0"> We can best understand a Preference Semantics approach to ill-formedness by comparing it with Katz and Postal's (1964) semantic markers/selection restriction approach. Katz and Postal's approach embodies a binary principle of semantic well-formedness similar to that assumed in standard generative syntax: well-formed and ill-formed.</Paragraph> <Paragraph position="1"> A selection restriction is binary - a semantic marker either fits a selection restriction or it does not. Preferences-as-restrictions, as they appear in semantic formulas, are also binary (and equivalent to selection restrictions): a semantic class either satisfies a preference or it does not. With the binary principle, there is an absolute criterion for ill-formedness: a semantic relation can be labelled ill-formed by examining that relation alone, without looking at any others.</Paragraph> <Paragraph position="2"> At the level of the constituent or sentence, preference-as-procedure is different from a selection restrictions approach. This should be clear if we examine a selection restrictions approach using the same four elements we used for preference-as-procedure: * production - only those sentence readings with all their selection restrictions fulfilled are produced; null * scoring- there are only two scores - (i) &quot;wellformed&quot;: all selection restrictions fulfilled, or (ii) &quot;ill-formed&quot;: one or more restrictions are violated; * comparison - none. Readings are conSidered individually, without comparison against other readings; * selection - the sentence reading with all selection restrictions fulfilled is taken, if such exists.</Paragraph> <Paragraph position="3"> The preference approach adopts a different, unary principle of &quot;formedness&quot;. If a preference in a sentence is violated, then a reading is still produced for that sentence, so being &quot;formed&quot; is like being well-formed in the selection restrictions sense.</Paragraph> <Paragraph position="4"> But whether that (preference violating) reading is accepted as if it was well-formed, or rejected as if it was ill-formed, depends on whether there are other possible readings for that sentence and on the nature of these readings: * The reading is accepted if either there are no other readings for the sentence or if all the other readings for the sentence have more prefer-American Journal of Computational Linguistics, Volume 9, Numbers 3-4, July-December 1983 181 Dan Fass and Yorick Wilks Preference Semantics, III-Formedness, and Metaphor ence violations. In such situations, the PS system assumes that the writer meant to produce the reading, that is, that it is some novel use of language (for example, metaphor) and is wellformed. null * The reading is rejected if there is another reading for the sentence that has fewer preference violations. However, being rejected in this way is probably not tantamount to being ill-formed because, in some other circumstances, sentences containing a preference violation (like the rejected reading) could be accepted as the best available.</Paragraph> <Paragraph position="5"> If all the preferences are fulfilled in a reading of a constituent, then, although the constituent/sentence may be &quot;well-formed&quot; in the selection restrictions sense, that reading may not necessarily be accepted.</Paragraph> <Paragraph position="6"> This is because there may be another reading of the same sentence that also has all of its preferences satisfied and is equally acceptable.</Paragraph> <Paragraph position="7"> So, the difference between PS and Katz and Postal's approach is at the procedural level. With the unary principle of PS, the criterion for ill-formedness is relative: a reading can only be labelled &quot;ill-formed&quot; after comparing it with other readings, and not by examining that reading alone, which is why preference-as-procedure produces all readings, whether or not they contain preference violations.</Paragraph> <Paragraph position="8"> So, we have distinguished two criteria for illformedness: absolute and relative. Within PS, the criterion of absolute ill-formedness is used for the semantic relations between individual word-senses (3.1.), and relative ill-formedness for readings of constituents of sentences (3.2.).</Paragraph> <Paragraph position="9"> 4.2. The nature of preference violations Preference violations between two words can be caused either by some &quot;total&quot; mismatch of wordsenses, as between \[interrogates\] and \[crook (thing)\] in (4b); or by some metaphorical relation, as there is between \[car\] and \[drink\] in (1) The car drank gasoline. Examining the preference violation itself does not reveal its nature; we can only discover the type of preference violation by examining competing readings (if any), which is what preference-as-procedure does. If all the other readings have more preference violations, then the reading containing the single preference violation is assumed to be appropriate and a metaphor.</Paragraph> <Paragraph position="10"> However, we can produce sentences containing a metaphor in which examining the alternative sentence readings cannot help establish what type of preference violation we have. Consider the sentence (5) That chopper drinks gasoline which contains a metaphor (Van Eynde 1982).</Paragraph> <Paragraph position="11"> There are two readings of the sentence, based on the ambiguity of chopper as either &quot;ax&quot; or &quot;helicopter&quot;. The two template representations are: (Sa) \[chopper (helicopter)\] \[drinks\] --- \[gasoline\] (5a) \[chopper (ax)\] \[drinks\] --- \[gasoline\] Both \[chopper (helicopter)\] and \[chopper (ax)\] have the semantic head THING (physical object), and both violate the preference of \[drink\] for an ANIMATE agent. In this example, the PS system cannot discriminate between the two sentence readings - one containing mismatched word-senses (5b), the other containing a metaphor (5a) - in terms of their number of satisfied preferences. So it is unable to decide which reading is metaphorical (and appropriate).</Paragraph> <Paragraph position="12"> Because a preference violation locates failed semantic relations, we can try to determine whether or not that violation is caused by a metaphor by applying additional semantic information there. In the next section we consider the sort of semantic information necessary to resolve (5) and one suggested way of representing that information.</Paragraph> </Section> </Section> <Section position="8" start_page="0" end_page="0" type="metho"> <SectionTitle> 5. Semantic Information about Metaphor </SectionTitle> <Paragraph position="0"> Van Eynde (1982) has pointed out that the standard PS system cannot choose the correct reading from templates (5a) and (5b) above. He suggested a set of rules, polysemy rules, that can recognise one of the violations as being caused by a metaphor and choose the correct reading.</Paragraph> <Paragraph position="1"> Polysemy rules are applicable to metaphors involving a predicate and a non-predicate; they can be used not only to choose between readings like (5a) and (5b) but also to confirm that a single reading produced for a sentence like (1) is a metaphorical one. Metaphors between two non-predicates, for example &quot;This encyclopaedia is a gold-mine (Rumelhart 1979), are excluded from consideration in this paper.</Paragraph> <Paragraph position="2"> It is very important to divorce two issues concerning PS and metaphor: first, ways of recognising and choosing a reading containing a metaphor, that is, polysemy rules, described in section 5.1. below; second, possible strategies for representing that metaphorical reading, described in section 6. Polysemy rules can be combined with a number of those strategies.</Paragraph> <Section position="1" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 5.1. Polysemy rules What is essential first of all is to provide additional </SectionTitle> <Paragraph position="0"> semantic information to distinguish the vehicle sense from the ax sense of chopper. Van Eynde introduces a new primitive VEHICLE, which he uses as head primitive of the vehicle sense of chopper.</Paragraph> <Paragraph position="1"> A polysemy rule looks like this: (6) condition: certain environmental data, such as: A is the AGENT slot of a template and B is an action in the ACTION 182 American Journal of Computational Linguistics, Volume 9, Numbers 3-4, July-December 1983 Dan Fass and Yorick Wilks Preference Semantics, III-Formedness, and Metaphor slot of the same template. Subject preference of B --- ANIMATE. Head primitive of A = VEHICLE.</Paragraph> <Paragraph position="2"> assignment: Head primitive of A := ANIMATE.</Paragraph> <Paragraph position="3"> The format of the above we take to be self-evident. The rule would normally be understood to run its assignment whenever the condition is satisfied. On a historical note one can compare polysemy rules with the very general dictionary extension rules of Givon (1967).</Paragraph> <Paragraph position="4"> The effect of this particular rule is to change data, that is to alter the head primitive of the helicopter sense of chopper. Note that, with rules of this type, the assignment can either * change the data by modifying the inherent semantic information in the non-predicate (thus making it animate), so that the unchanged semantic formula for drink (preferring an animate agent) will still pick out this reading; or, * alternatively, one could change the expectations, modifying the semantic formula for drink (the predicate), so that it accepts vehicular agents as second best to genuinely animate ones; or, * one could modify \[drink\] more radically, by changing its inherent data (see below); or, * we could just leave both formulas unchanged.</Paragraph> <Paragraph position="5"> We will consider these four alternatives in section 6.</Paragraph> </Section> <Section position="2" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 5.2. Discussion </SectionTitle> <Paragraph position="0"> The first point to note is that polysemy rules alone do not provide a means of recognising the initial conflict between chopper and drinks, and does not provide a means of selecting the sentence reading containing the correct sense of chopper. Thus, polysemy rules cannot operate on their own but only within some more general word-sense disambiguation mechanism such as PS, in some such way as the following: for sentence (5), only after the template expansion algorithm of PS has produced the two readings (5a) and (5b) can polysemy rules be applied to the non-predicate involved in the preference violation, and the template expansion algorithm tried again. One of the readings for the sentence will now have no preference violations (5c) \[chopper (helicopter)\] --,- \[drinks\] --- \[gasoline\] and is accepted.</Paragraph> <Paragraph position="1"> In the foregoing (5.1.), we have embedded Van Eynde's polysemy rule (6) within some general PS environment for making choices between readings after (6) has altered the available readings. It was necessary to do this because, as we pointed out, the rule alone does not specify how to select readings.</Paragraph> <Paragraph position="2"> Moreover, Van Eynde sees rules like (6) as operating within a production system. If that production system was uncontrolled, then such rules would run whenever their conditions were satisfied. The control regime for those rules is hard to imagine, and would certainly be very complex.</Paragraph> </Section> </Section> <Section position="9" start_page="0" end_page="0" type="metho"> <SectionTitle> 6. The Representation of Metaphor and Ill- </SectionTitle> <Paragraph position="0"/> <Section position="1" start_page="0" end_page="0" type="sub_section"> <SectionTitle> Formed Input </SectionTitle> <Paragraph position="0"> In this section we describe and compare four strategies for representing ill-formed input in general and metaphors in particular, in semantic representations. It is assumed that a process with the power of that described in section 5 above has located a preference violation or &quot;semantic conflict&quot; and recognised it as being a metaphor.</Paragraph> <Paragraph position="1"> 6.1. Four strategies for the representation of metaphor We will illustrate these strategies using sentence (1) The car drank gasoline though we could also have considered reading (5a) of sentence (5) as an example. The best reading for (1) has a conflict between the expectation of the predicate \[drink\] expecting an animate agent as subject and the data in the non-predicate because the actual subject (the car) is inanimate. If we built a semantic representation of this sentence, then the conflict would remain in the representation.</Paragraph> <Paragraph position="2"> Obvious strategic choices are: (i) Passive strategy Relax the preference of the predicate and accept the semantic representation with the conflict unresolved (Wilks 1975); at no point are data or expectations changed, and the analysis system simply accepts the representation it is given.</Paragraph> <Paragraph position="3"> (ii) CTD, or Change The Data, strategy Change the inherent data in the non-predicate in such a way that it meets the expectations (Van Eynde 1982). So, in sentence (1) alter the data and replace the head primitive VEHICLE in \[car\] by the primitive ANIMATE in the semantic representation. This is one top-down (expectation driven) approach: in the case of conflict between what you have and what you expect, change what you have and be guided by your expectations.</Paragraph> <Paragraph position="4"> (iii) CTE, or Change The Expectations, strategy Change the expectations in the predicate in such a way that they meet the data (Van Eynde 1982).</Paragraph> <Paragraph position="5"> So, for sentence (1) alter its semantic representation by changing the expectation that the subject of \[drink\] must be ANIMATE to VEHICLE (iv) Active strategy A more radical approach, explored in Wilks (1978), would produce a completely new formula \[drink\] by rule and equivalent to \[consume\], modifying inherent and expectational data, so as to accept an animate agent (car). This approach uses the wider context of frame-like representations, called pseudo-texts, in addition to semantic American Journal of Computational Linguistics, Volume 9, Numbers 3-4, July-December 1983 183 Dan Fass and Yorick Wilks Preference Semantics, III-Formedness, and Metaphor formulas. At its crudest the method consisted of finding particular facts (when faced with (1)) about cars in its frame-like data base such that cars did operate on gasoline in a manner semantically related to drinking. The only fact located was &quot;cars consume gasoline&quot; and so a \[drink\] had a new representation added, namely the appropriate formula from the dictionary entry for \[consume\]. This is a top-down, knowledge-driven approach, but cannot be termed CTE or CTD since no formula of drink is modified but a new one slotted into the templates for that particular ill-formed locution. We shall compare this method with the others above, that need less detailed and cumbersome context than frame methods and are more narrowly semantic.</Paragraph> <Paragraph position="6"> 6.2. Comparison of the four strategies The strategies are compared in two ways. First, the degree to which the semantic representations containing metaphors produced by the different strategies correspond to human understanding of those metaphors. Given the shallowness of a PS representation, that correspondence can be no more than superficial.</Paragraph> <Paragraph position="7"> Secondly, whether or not the semantic representations of the different strategies would assist in concrete computational tasks, such as producing correct translations. null Most, if not all, individual metaphors can be read or understood in two ways. For example, the metaphor in (1) can be understood either by viewing the predicate drink as the car-like consuming of petrol, or by seeing the non-predicate car as having some human properties. Within PS, the CTE strategy and the active strategy reflect the first, predicate reading by altering semantic information in the predicate; the CTD strategy reflects the second, non-predicate reading by changing inherent information in the non-predicate.</Paragraph> <Paragraph position="8"> No single strategy reflects both readings. By leaving the preference violation in the semantic representation, the passive strategy does not reflect either reading and does not reflect human understanding of metaphor at all.</Paragraph> <Paragraph position="9"> In extended metaphors (those beyond a single clause), the initial metaphorical reading can be carried over in either the non-predicate or the predicate.</Paragraph> <Paragraph position="10"> Consider the following extended metaphors that are also cases of gapping (Hankamer 1973): (7) The car drank gasoline and (the car) purred to itself (8) The car drank gasoline and the taxi (drank) diesel In (7), the metaphorical usage of the non-predicate car is continued; in (8), it is the predicate drink.</Paragraph> <Paragraph position="11"> We now examine how closely the strategies of 6.1.</Paragraph> <Paragraph position="12"> reflect our understanding of extended metaphors like (7) and (8). To do this, we shall assume a simplified form of rules for filling dummy template nodes (Wilks 1975). Those more familiar with Chomsky (1977) can think of this in terms of a form of trace mechanism in which the trace node in the template representing the second clause inherits information from the controlling node in the first clause. Hence in (7) the formula of car will be inherited by the empty agent node in the template containing \[purr\].</Paragraph> <Paragraph position="13"> Let us consider (7) first. What happens when each strategy encounters \[car\] and \[drink\] in the first clause of the sentence, and then encounters \[car\] inherited from the first template and \[purr\] in the second clause? When the CTD strategy encounters \[car\] and \[drink\], it removes the preference violation between them by reassigning VEHICLE as ANIMATE in the non-predicate \[car\]. This modified formula of \[car\] is inherited from the first template; \[purr\] expects an animate SUBJ and \[car\] is now ANIMATE, so there is no preference violation between them.</Paragraph> <Paragraph position="14"> The CTE strategy removes the preference violation between \[car\] and \[drink\] by changing the SUBJ preference of the predicate \[drink\] from ANIMATE to VEHICLE. \[car\] is unchanged and is inherited unchanged. Because \[car\] is still marked as inanimate, there is a preference violation with purr, which causes the CTE strategy to alter the SUBJ preference of \[purr\] to VEHICLE.</Paragraph> <Paragraph position="15"> The passive strategy does not change either \[car\] or \[drink\], leaving the preference violation between them. A second preference violation is left in the second clause as well.</Paragraph> <Paragraph position="16"> With the active strategy, a car-frame (or pseudotext) is used, and \[drink\] would have a new consume sense and there would be no effect on \[car\]. Hence, the frame would be accessed again for the second clause, but would either find no new sense for purr in the limited context of to itself (which would become just a passively accepted, though preference-violating, template) or it could hope to re-apply the active strategy and find from the car frame that the only noise cars were noted as making (other than in conditions of trouble where they would backfire, etc.) was hum, which could be imposed in place of \[purr\], and would be confirmed by a causal inference from the beneficial effect of \[consume gasoline\]. However, this might be difficult to embody in a serious knowledge representation since there is no non-metaphorical description-in English of the noise of cars.</Paragraph> <Paragraph position="17"> So for (7) the active and passive strategies both leave preference violations in the second clause. The CTE and CTD strategies do not, but of these two, the CTD strategy more closely reflects human understanding. null 184 American Journal of Computational Linguistics, Volume 9, Numbers 3-4, July-December 1983 Dan Fass and Yorick Wilks Preference Semantics, III-Formedness, and Metaphor Now let us examine (8), The car drank gasoline and the taxi diesel. When processing (8), the CTD strategy changes semantic information in the non-predicate \[car\]. \[drink\] is unchanged and is inherited unaltered by the second template. \[taxi\] is inanimate, but \[drink\] expects an animate subject, so there is a preference violation, which will cause the semantic information in \[taxi\] to be changed in its turn.</Paragraph> <Paragraph position="18"> The CTE strategy will change the SUBJ preference of the predicate \[drink\] to VEHICLE. This modified version of drink is then inherited by the second template. As \[taxi\] is a VEHICLE, there is no preference violation between \[drink\] and \[taxi\].</Paragraph> <Paragraph position="19"> The passive strategy changes neither set of information, which leads to preference violations in both clauses. The active strategy would construct a new consume sense for \[drink\] that would be inherited by the action node of the second template. As \[taxi\] is a VEHICLE, there would be no preference violation between \[taxi\] and the new sense of drink.</Paragraph> <Paragraph position="20"> In (8), where the metaphorical usage continued in the predicate, the CTE and active strategies most closely reflect human understanding because both have the effect of changing the predicate's expectations of , its subject. However, in (7), where the metaphorical usage continued in the non-predicate, the CTD strategy was best because it changed the inherent data in the non-predicate.</Paragraph> <Paragraph position="21"> If we take the production of correct translation as a minimum constraint on interpretation strategy, then the changes the four strategies make to semantic representations are important because the effect of one strategy can be to produce a correct translation while another can cause a mistranslation.</Paragraph> <Paragraph position="22"> Consider (9) The car drinks gasoline and (the car) does not work well where the metaphor in the first clause does not extend to the gapped second clause. Assuming a node inheritance mechanism once again, \[car\] will be inherited in the second clause.</Paragraph> <Paragraph position="23"> If the non-predicate \[car\] is inherited unaltered, then that sentence is translated correctly as La voiture boit de l'essence et ne march pas bien because marcher, the appropriate translation of work, expects an inanimate subject. It is because they leave \[car\] unchanged that the passive, CTE, and active strategies all produce the correct translation of (9).</Paragraph> <Paragraph position="24"> However, the CTD strategy reassigns \[car\] as ANIMATE, and this modified formula of car is inherited into the second template. The effect of this is to translate the sentence wrongly as La voiture boit de l'essence et ne travail pas bien because travailler, another translation of work, expects an animate subject. (9) is not meant to be taken as decisive evidence in favour of the CTE strategy or the frame-based active strategy. We are sure that sentences can be found where altering the predicate's semantic information would cause mistranslations, where only the CTD or passive strategy would produce correct translations (there are probably sentences for which the passive strategy would produce mistranslations too): a strategy that produces a correct translation for one sentence may well mistranslate another. It is not possible to pursue these possibilities in detail here because it would involve too much detail of the mechanisms by which a translation equivalent in the target language is located - for example, by a full semantic matching as in the MARGIE system (Schank et al. 1973), or from a prior guidance to possible target equivalents, as in Wilks (1973). That degree of detail would change the emphasis of this paper, in which translation is no more than a minimum condition that semantic strategies dealing with ill-formedness must meet.</Paragraph> <Paragraph position="25"> Because individual metaphors are ambiguous, that is, can be read or understood in two directions, no one strategy is adequate. The passive strategy is totally unsatisfactory. Strategies that alter the semantic information of non-predicates (CTD strategy) are inappropriate for predicate readings of individual metaphors and for extended metaphors that continue a predicate reading such as the one in sentence (8).</Paragraph> <Paragraph position="26"> Equally, we cannot have only strategies that alter the semantic information of predicates (CTE or active strategy) because of both non-predicate readings of individual metaphors and extended metaphors continuing a non-predicate reading like (7).</Paragraph> <Paragraph position="27"> As a result of the preceding comparison of strategies in terms of correspondence to human understanding and production of correct translations, it is clear that both strategies that change expectations and strategies that change data are needed. Since both these major types of strategy are fallible, how will the proper strategy be selected? In the next section we propose a control mechanism using both types of strategy that makes the correct selections (in terms of human understanding and accurate translations above), that is, it allows individual metaphors like the one in (9) to be represented by both types of strategy, selects the CTE strategy for examples such as (8), the CTD strategy for those such as (7), and no strategy at all for sentences like (10) The cat drank milk and the dog (drank) water that do not contain metaphor.</Paragraph> </Section> <Section position="2" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 6.3. Control of the strategies </SectionTitle> <Paragraph position="0"> In this section we consider only single representative examples of a strategy that changes expectations and one that changes data: these will be the CTE and CTD strategies. We limit our demonstration of the control mechanism to the sentences of 6.2. containing a gap-American Journal of Computational Linguistics, Volume 9, Numbers 3-4, July-December 1983 185 Dan Fass and Yorick Wilks Preference Semantics, III-Formedness, and Metaphor ped clause - that is, (7), (8), (9), and (10) - though we believe it to be generally applicable.</Paragraph> <Paragraph position="1"> We shall deal with the case of no metaphor first. If no metaphor is found in the first clause, as in (1), then a single template with the largest number of preferences is chosen in the normal way (see section 1).</Paragraph> <Paragraph position="2"> If, as in (7), (8), and (9), a metaphor is encountered in the first clause, then both major types of strategy are applied, producing two competing templates for the clause representing metaphorical ambiguity, that is, the two possible readings of the metaphor (data and expectations important to the metaphor are included below): Any semantic formula whose semantic information has been altered is marked by the control mechanism (indicated above by an *). The template (lla) produced by the CTE strategy has an altered predicate \[drink\]; the template (lib) produced by the CTD strategy has an altered non-predicate \[car\].</Paragraph> <Paragraph position="3"> If the second clause is a case of gapping, then the dummy node in the second template is analysed. If there is a single (unmarked) template representing the first clause, then the first clause did not contain a metaphor and the dummy node in the second template inherits the semantic formula from the controlling node in the first template in the way described earlier (section 6.2.). Hence, for (10), \[drink\] is inherited.</Paragraph> <Paragraph position="4"> If there are two (marked) templates representing the first clause, as with (lla) and (llb), then a metaphor is present. Though the mechanism also operates if the dummy node in the second template is a predicate (as in (8)), let us suppose that the missing node is a non-predicate, as in (9) The car drinks gasoline and does not work well or (7).</Paragraph> <Paragraph position="5"> To allow for individual metaphors like (9), the control mechanism assumes that the metaphor in the first clause has not been continued in the second: an unaltered version of the non-predicate is placed in the dummy node of the second template, taken from the template with an altered predicate because it contains the unaltered non-predicate. So, for sentence (9), the unaltered \[car (VEHICLE)\] is taken from the template with the altered predicate (lla), and a new template for the second clause (shown below in much simplified form) is produced: (12) \[car (VEHICLE)\] ~ \[works (SUBJ VEHICLE)\] If there is no preference violation between that unaltered non-predicate and the other nodes of the second template, then, provided no other reading has more satisfied preferences, it is that reading of the template that is accepted.</Paragraph> <Paragraph position="6"> If, though, we have a case of extended metaphor as in (7) The car drank gasoline and purred to itself, then there is a preference violation between the unaltered non-predicate \[car (VEHICLE)\] and the predicate in the template for the second clause. So, for (7), the following template (much simplified) is produced: (13) \[car (VEHICLE)\] \[purred (SUBJ ANIMATE)\] (13) must have more satisfied preferences than any other competing template but - and here the control mechanism departs from the standard preference-as-procedure - even if (13) has more satisfied preferences than any other template, it is not accepted as it is, because it contains a preference violation between \[car\] and \[purr\]. Instead, a new template for the second clause is created: its empty node is filled with the altered version of the same formula \[car (ANIMATE)\], inherited from the other template representing the first clause (llb), the one containing the amended nonpredicate: null (14) \[car (ANIMATE)\] ~ \[purred (SUBJ ANIMATE)\] This template is accepted if it has more satisfied preferences than any other. Because the second case of inheritance was from the template containing the amended non-predicate, the control mechanism knows that the CTD strategy was appropriate for the first clause: the template containing the amended nonpredicate, appears in the semantic representation for the sentence as a whole. Hence the control mechanism handles cases of extended metaphor like (7) and (8).</Paragraph> <Paragraph position="7"> However, for sentences containing a single metaphor such as (9) and (1), the ambiguity of the metaphor remains unresolved as two possible templates, (lla) and (llb). In terms of the means of comparison used in 6.2. (correspondence to human understanding and production of correct translations), there is no need to keep both templates, so the template with the altered predicate is retained (the product of the CTE or active strategy), somewhat arbitrarily, because we believe this reading to be the more common of the two.</Paragraph> </Section> </Section> class="xml-element"></Paper>