File Information
File: 05-lr/acl_arc_1_sum/cleansed_text/xml_by_section/metho/95/j95-1001_metho.xml
Size: 69,378 bytes
Last Modified: 2025-10-06 14:13:59
<?xml version="1.0" standalone="yes"?> <Paper uid="J95-1001"> <Title>Principled Disambiguation: Discriminating Adjective Senses with Modified Nouns</Title> <Section position="4" start_page="2" end_page="3" type="metho"> <SectionTitle> 2. Word Sense Indicators </SectionTitle> <Paragraph position="0"> Our problem is a specific case of the more general problem of finding clues within the context of a word that indicate its sense fairly reliably. Content words that have a close syntactic relation to one another are useful candidates for examination and are intuitively more likely to bear a close semantic relation than words that are near one another but are not related syntactically. One much-studied example is the semantic relation between a verb and its arguments (e.g., Boguraev et al. 1989; Church and Hanks 1989; Braden-Harder 1991; Hindle and Rooth 1991).</Paragraph> <Paragraph position="1"> Discrimination among senses of adjectives based on the nouns they modify or of which they are predicated has been the subject of less intensive and systematic study.</Paragraph> <Paragraph position="2"> Determining the potential of this line of evidence is the focus of this paper. We do this by performing a noun-based disambiguation experiment. Certainly, some nouns are strongly associated with particular senses of some of the adjectives that modify them.</Paragraph> <Paragraph position="3"> This association can be illustrated for the ambiguous adjective old, which has senses roughly synonymous with aged, long existing, former, used, and obsolete, using sentences from our experimental corpus (see Section 4.1). Two of the nouns most frequently modified by old in general texts are man and house. Overwhelmingly, old is used in the sense 'aged (not young)&quot; when it modifies man, e.g., in The man was very old and very frail, a widower.</Paragraph> <Paragraph position="4"> He was a strong old man: he had lived through forty-five years of those wretched casseroles, but she missed him already.</Paragraph> <Paragraph position="5"> &quot;Guilty!&quot; came the hoarse croaking sounds of the old men.</Paragraph> <Paragraph position="6"> In some sentences, in fact, this noun is the only real basis, within the sentence itself, for inferring the sense of old: The old man answered this time.</Paragraph> <Paragraph position="7"> &quot;Leave the other to the old man.&quot; &quot;All except the old man.&quot; Man, therefore, can be taken as a fairly good indicator of the 'aged' sense of old. Similarly, when old modifies house, it almost always has one of its 'not new' senses, as in In the fashionable suburb of Kingston, full of beautiful old houses...</Paragraph> <Paragraph position="8"> ... around the old Holton house he made many improvements...</Paragraph> <Paragraph position="9"> He saw the tractors come and tear down the old houses and plow up the land... When old modifies house, then, this is a good indication that old is being used in one of these senses. So man and house are reliably associated with different senses of old. We refer to man and house as indicators for the senses of old. More generally, a feature F (such as the modified noun man) that is associated with a target word T Computational Linguistics Volume 21, Number 1 (such as the modifying adjective old) is an indicator for a sense Si (e.g., 'aged') of T if, when the feature is present, that sense Si is more likely than the other senses Sj, j -~ i. This statement is formalized in the Appendix.</Paragraph> <Paragraph position="10"> This characterization of the indicators for word senses also provides flexibility regarding sense definition. Not only does it not require a single assessment, once and for all, concerning what the senses of a word may be, it requires no commitment to the reality of word senses themselves, as classically construed (see Pustejovsky and Boguraev 1993). Disambiguation may be pursued relative to many distinct issues, e.g., grammatical class, functional role, document topic, or lexical translation equivalent; the entities to be discriminated are the effective &quot;senses&quot; being identified. In this paper, we disambiguate relative to a pair of word sense groups, operationally by disambiguating relative to sense-specific antonyms; an old man, for example, is a man who is not young, and an old house is a house that is not new. Such sense distinctions have some justification in terms of the semantic organization of adjectives (see Gross, Fischer, and Miller 1989). However, our purpose in choosing them was purely for convenience in designing an experiment useful for determining the potential of noun-based disambiguation of adjectives.</Paragraph> <Paragraph position="11"> The characterization of indicators is equally flexible with regard to the domain of its own applicability. It need not be assumed that all instances of the target word T are to be included in assessing the relative probabilities of different senses. In the experiment described here, we are determining the extent to which those senses of an adjective that are associated with one antonym can be distinguished from those associated with a different antonym according to the nouns that the target adjective modifies. We therefore discriminate between just these two sets of senses, which constitute the great majority of instances of the targets, and we exclude from both investigation and evaluation all instances in which the sense of the target does not fall in one of these two groups. We exclude all freezes from consideration as not being legitimate instances in which the adjectives actually have a definable sense (see footnote 1). In addition, we exclude the minority of instances that have definable senses that do not fall within these two groups. For example, short has a sense 'inadequate' that is related historically to its dimensional senses; however, this sense does not have a lexically specific antonym, whereas the dimensional senses do (long and tall).</Paragraph> </Section> <Section position="5" start_page="3" end_page="5" type="metho"> <SectionTitle> 3. Disambiguated Subcorpora </SectionTitle> <Paragraph position="0"> To extract a reasonable number of nouns that are indicators for the senses of target adjectives, one straightforward approach would be to extract a representative sample of sentences for each target adjective, to disambiguate each target manually, and to extract those nouns that are relatively frequent and that are modified by the target in one sense but not in the other. We adopted a different strategy, one that provided us with a large set of sentences in which target adjectives could be disambiguated automatically and with complete reliability. This strategy involved disambiguation of adjectives by their co-occurrence with sense-specific antonyms.</Paragraph> <Paragraph position="1"> Antonym co-occurrence is a frequent and pervasive phenomenon, and it takes place under highly restricted semantic and syntactic conditions (Charles and Miller 1989; Justeson and Katz 1991, 1992). An adjective and its antonym refer to opposed values of the same attribute. When they modify the same noun in a sentence this is the usual case in sentences in which they both occur--this attribute is virtually ensured of applying in a consistent way to both instances of the noun. When an adjective like old has different senses that are associated with different antonyms (like new and young), the adjective in these sentences is disambiguated by its antonym. Thus, in sentences John S. Justeson and Slava M. Katz Principled Disambiguation in which old and young modify the same noun, e.g., man, old is thereby interpretable as 'not young'; in those in which old and new both modify a noun, e.g., house, old is thereby interpretable as 'not new.' The reason for this effect is easy to observe. Antonyms most often co-occur in direct comparisons or in contrastive opposition, directly reflecting both the identity of the attribute to which they pertain and the contrast in its value. As illustrated by the following sentences from the Brown Corpus (Francis and Kucera 1982), they usually occur in otherwise essentially identical phrases: Photograph shows the wrong side of work with light strand being picked up under dark strand in position to be purled.</Paragraph> <Paragraph position="2"> They indicated that no new errors were being made and that all old errors would be corrected within 60 days.</Paragraph> <Paragraph position="3"> Note how easy it is to find synonyms for the epithet &quot;miser&quot; and how hard to find synonyms for &quot;spendthrift.&quot; When her right hand was incapacitated by the rheumatism, Sadie learned to write with her left hand.</Paragraph> <Paragraph position="4"> I found myself becoming one of that group of people who, in Carlyle's words, are forever gazing into their own navels, anxiously asking am I right, am I wrong? Radio broadcasts, however--now that even plain people could afford loud speakers on their sets--held old fans to the major-league races and attracted new ones...</Paragraph> <Paragraph position="5"> We often say of a person that he looks young for his age or old for his age.</Paragraph> <Paragraph position="6"> We refer to this pattern as phrasal substitution. In these cases, the phrases involved usually stand in direct semantic opposition (e.g., her right hand .... her left hand). Co-occurring antonyms are also frequently joined by and or or, or appear in noun phrases joined by prepositions and having the same head noun: It was pitiful to see the thin ranks of warriors, old and young...</Paragraph> <Paragraph position="7"> That was one more reason she didn't look forward to Cathy's visit, short or long; As for this rider, I never saw him before or afterwards and never saw him dismounted, so whether he stood tall or short in his shoes, I can't say; Skin colors range from white to dark brown, heights from short to tall, hair from long and straight to short and tightly curled.</Paragraph> <Paragraph position="8"> It was a winter world without details, a world of shapes in an expanse ranging in color from light to dark gray.</Paragraph> <Paragraph position="9"> But there is no sudden transition from hard rock to soft.</Paragraph> <Paragraph position="10"> The chief function of these conjoined and prepositional co-occurrences is to cover the range of possible values of an attribute.</Paragraph> <Paragraph position="11"> Whether the antonym co-occurrences involve contrastive opposition or a range of attribute values, they call forth the semantic dimension designated by the antonym pairs and guarantee concordance in adjective sense of the co-occurring antonyms. Thus, when an adjective has different sense-specific antonyms, their co-occurrences Computational Linguistics Volume 21, Number 1 as modifiers of different instances of the same noun reliably disambiguate that adjective. Five common English adjectives have such antonyms, yielding ten antonymous adjective pairs: hard-easy, hard-soft; light-dark, light-heavy; old-new, old-young; rightleft, right-wrong; and short-long, short-tall. All the example sentences above involve one of these ten pairs, and they exemplify the concordance of the antonyms' senses. Furthermore, certain departures from the perfect phrasal substitution patterns equally constrain the senses of the antonyms to be concordant. These departures include insertion of adverbial modifiers, substitution of other words besides the antonyms, or use of the antonyms to modify noun phrases having the same head noun in phrases that otherwise differ from one another. The subcorpora that were used in the work reported here consist of those sentences in which a target adjective and its antonym modify separate instances of the same noun or clause.</Paragraph> </Section> <Section position="6" start_page="5" end_page="13" type="metho"> <SectionTitle> 4. The Experiment </SectionTitle> <Paragraph position="0"> This section describes our investigation of noun-based disambiguation and its results.</Paragraph> <Paragraph position="1"> Subcorpora were extracted for each of the five target adjectives, consisting of sentences in which the target was disambiguated by its co-occurrence with an antonym as modifiers of the same noun (Section 4.1). The tendency toward sense specificity of nouns modified by target adjectives in these sentences is demonstrated by showing that there is little overlap in the set of nouns modified by the target in the two antonym co-occurrence subcorpora for that target (Section 4.2). Nouns indicating the antonym-specific senses of these targets were then extracted by statistical analysis of their sense preferences. It is shown that these indicator nouns are also specific to the senses of the target adjectives in the corpus at large by using them successfully in a disambiguation procedure applied to 500 randomly selected sentences (Section 4.3).</Paragraph> <Paragraph position="2"> Simple, broadly applicable semantic features characterize most of the indicator nouns, whereas broadly applicable syntactic features characterize many of their contexts. Together, these features discriminate the target senses, permitting a more compact and conceptual rather than word-specific representation of the indicators (Section 4.4): about three-quarters of the adjective instances are disambiguated by these features, and virtually errorlessly.</Paragraph> <Section position="1" start_page="5" end_page="5" type="sub_section"> <SectionTitle> 4.1 Acquiring Disambiguated Subcorpora </SectionTitle> <Paragraph position="0"> Our original study of antonym co-occurrence (Justeson and Katz 1991) was based on a version of the Brown Corpus, containing 54,717 sentences; it yields only 57 sentences in which both adjectives from any of the ten antonym pairs analyzed in the present study were modifying different instances of the same noun. To get enough sentences containing antonym co-occurrences of antonyms to address disambiguation issues adequately, we used the 1.5 million-sentence APHB Corpus. This corpus of 25,000,000 words was obtained from the American Printing House for the Blind and archived at IBM's T.J. Watson Research Center. It consists of stories and articles from books and general circulation magazines.</Paragraph> <Paragraph position="1"> All sentences containing co-occurrences of the target adjective and each of its antonyms were extracted from the APHB Corpus, yielding 4391 sentential co-occurrences. These sentences were manually postprocessed to eliminate all instances in which either the target or its antonym was not being used adjectivally. 2 From the 2 This could have been automated using a parser. Our immediate interest, however, is in discovering actual patterns of usage and not in building an automatic system. We did the work manually to avoid John S. Justeson and Slava M. Katz Principled Disambiguation remaining sentences, we further extracted a subset of sentences in which both members of the pair modify distinct instances of the same noun. This yielded 1487 sentences in which at least one of the target adjectives co-occurs with one of its antonyms, with both the target and its antonym modifying instances of the same noun that are in separate phrases. Some of these sentences have more than one such co-occurrence, so these sentences yielded 1535 total co-occurrences. Every one of these co-occurrences had sense-concordant antonyms modifying the same noun; any other sense is usually semantically incongruous, especially in direct phrasal substitutions. The sentences in which co-occurring antonymous adjectives modify the same noun therefore constitute a subcorpus in which the ambiguous members of the antonym pairs are discriminated relative to their antonym-specific senses. This gave us ten subcorpora, one for each antonym pair, of 1535 examples to use as a database for studying the extent to which modified nouns disambiguate their modifying adjectives.</Paragraph> <Paragraph position="2"> In counting instances of nouns associated with each adjective, elided nouns and anaphoric pronouns were resolved (manually) whenever possible, adding to the counts for the noun referent, since we are studying the phenomenon of the adjective-noun relation. In addition, we stripped morphological suffixes from noun phrases, to recover an adjective-noun base. Thus right winger, right fielder, and heavy sleeper are recognized as deriving from right wing, right field, and heavy sleep; short-staffed, short-lived, and light industrial are recognized as derived from short staff, short life, and light industry. It was counted directly only in non-anaphoric usage. The sentences of this subcorpus contain 1535 such co-occurrences of the target adjectives and their antonyms. (Co-occurrence counts for each of the ten antonym pairs are given in Table 3 of the Appendix.)</Paragraph> </Section> <Section position="2" start_page="5" end_page="5" type="sub_section"> <SectionTitle> 4.2 Specificity of Nouns for Adjective Senses in the Disambiguated Subcorpora </SectionTitle> <Paragraph position="0"> The disambiguated subcorpora can be used to assess the extent to which target adjectives, when modifying a given noun, are specific to a single sense rather than being usable in either sense. They are in fact surprisingly consistent in this regard, as can be illustrated for the indicator nouns discussed in Section 2. There it was noted that man is an indicator of the 'aged' sense of old (with antonym young) and house for some of the 'not new' senses of old (with antonym new).</Paragraph> <Paragraph position="1"> The specific association of man with the 'aged' sense of old is reflected in the use of this noun in antonymic constructions. The APHB Corpus contains 64 sentences in which both young and old modify man; e.g., In Bihzad's paintings we see people and animals as individuals--rich men and poor men, old and young, the elders in the mosque and the herdsmen camping among their horses in the fields.</Paragraph> <Paragraph position="2"> Old men saw visions and young men dreamed dreams.</Paragraph> <Paragraph position="3"> I am an old man, you a young one;...</Paragraph> <Paragraph position="4"> The old man turns to the young one and says: &quot;The time has come for a few questions.&quot; In both the old and the young man this was a breach of habit.</Paragraph> <Paragraph position="5"> Most of these sentences involve phrasal substitution patterns typical of antonyms generally. In contrast, there is not one sentence in which both old and new modify either man or men.</Paragraph> <Paragraph position="6"> the systematic errors to which all automatic parsers are subject.</Paragraph> <Paragraph position="7"> Computational Linguistics Volume 21, Number 1 The converse result obtains in the case of house. Four sentences contain instances in which old and new both modify house or houses: Cast-iron balustrades became the fashion, to be sought out when old houses were pulled down and removed to new houses...</Paragraph> <Paragraph position="8"> ... entire crates of dishes have been smashed when the trailers cross railroad tracks or other rough spots located between the old and the new house.</Paragraph> <Paragraph position="9"> Fireplaces in the new house, but not in the old one? Section 235 (of the Housing Act of 1968) helps families with low and &quot;moderate&quot; incomes to buy one- or two-family houses, old or new.</Paragraph> <Paragraph position="10"> In contrast, the APHB Corpus contains no sentence in which both old and young modify house or houses.</Paragraph> <Paragraph position="11"> The specificity of man and house to particular senses of old is typical of nouns in these subcorpora. Most nouns by far were modified by the target in only one of its senses, in our co-occurrence sentences. We demonstrated this sense specificity of modified nouns by compiling all pairs consisting of a target adjective modifying the same noun as either of its antonyms. For each of these adjective-noun pairs, we determined the number of instances involving each sense; we want to determine the extent to which a particular adjective-noun pair tends to occur with only one of the two senses. One hundred and eighty-one adjective-noun pairs occur more than once, 3 with a total of 1096 occurrences. Most by far have n : 0 sense distributions, i.e., the pairs occur in only one of the target's senses. Sixty-one adjective-noun pairs, covering 828 instances, have 4 or more instances each, and thus could admit 2 or more instances in their minority sense. Only 4 do have so many minority instances, covering 39 of the 828 total occurrences. The occurrence of 2 or more minority instances is not mainly a frequency effect; these 4 adjective-noun pairings are no more frequent on average than those that do not. So adjective-noun pairs do, as a rule, strongly favor one particular sense, and this is as true of pairs with many instances as of those with few.</Paragraph> </Section> <Section position="3" start_page="5" end_page="11" type="sub_section"> <SectionTitle> 4.3 Adjective Disambiguation Using Indicator Nouns </SectionTitle> <Paragraph position="0"> The specificity of nouns in the disambiguated corpus for senses of the target adjectives suggests potentially very high reliability for a noun-based procedure to disambiguate common adjectives. We evaluate the potential of such a procedure by extracting, from the co-occurrence sentences, a set of nouns that are indicators for the senses of the target adjectives and applying them to instances of the targets from non-co-occurrence sentences in the corpus at large.</Paragraph> <Paragraph position="1"> Because adjectives co-occur with their antonyms fairly frequently, it was practical to extract disambiguated subcorpora large enough to provide a base for statistical inference. However, subcorpora in which most sentences exhibit phrasal substitution of antonyms are clearly not representative samples of the use of the target adjectives.</Paragraph> <Paragraph position="2"> This raises the possibility that the specificity of nouns for target adjective senses might be influenced by the nature of the sentences in which they occur--those that contain largely repeated, contrastive structures; we need evidence concerning their sense specificity from the corpus at large. This unrepresentativeness also introduces bias into the 3 If a pair occurs only once, there is no opportunity for its target adjective to appear sometimes in one sense and sometimes in another; so such pairs cannot be used in estimating the consistency of sense selection by nouns.</Paragraph> <Paragraph position="3"> John S. Justeson and Slava M. Katz Principled Disambiguation statistical process of inferring sense indicators for the corpus at large from the specially selected subcorpora, a bias for which we must correct. The Appendix gives the formula needed to project, from the disambiguated subcorpora to the corpus at large, the probability of each sense of the target adjective given the noun it modifies. This adjustment for bias requires that we know the sense distribution of the target adjectives in the corpus to which the indicators are intended to apply and the number of instances in the subcorpora in which each potential indicator noun is modified by the target adjective in each of its senses.</Paragraph> <Paragraph position="4"> We therefore extracted from the APHB Corpus a random sample of 100 sentences containing adjectival instances of each target adjective, for a total of 500 sentences in all. In addition to requiring that the target word functions as an adjective, we exclude all freezes, 4 as well as quantificational expressions such as three years old in which the target labels an attribute (e.g., age) rather than a value of that attribute (e.g., 'aged'). 5 The target adjectives in all 500 test sentences were manually disambiguated, both with respect to the antonyms and in some cases with respect to other senses not associated with either antonym. The distribution of antonym-related senses is given in the third column of Table 1. Since we are interested in discriminating between the two antonym-related sets of senses of the targets, we limited attention to those instances of that target occurring in a sense for which an antonym exists. For this reason, the total number of instances is less than 100 for each target adjective, varying from 89 for hard to 99 for right. After determining the sense distribution for the target in each set, we could project which nouns in the subcorpora are likely to be sense indicators for the target adjectives in these samples.</Paragraph> <Paragraph position="5"> The following nouns were projected to show a preference for one or the other sense of the target adjectives that was statistically significant at the .05 level (nouns are in roman, classes in italic): hard-not easy: it, clauses hard-not soft: none light-not dark: none light-not heavy: cruiser, harness, load old-not new: proper names (of things), world, thing, car, way old-not young: man, people, proper names (of people), woman, proper names (of places), lady, you, wine, person, bull, he, I, one (animate pronoun) right-not left: hand right-not wrong: he, I, thing, way, what, clauses, answer, proper names (of people), act, country, decision, expert, masturbation, note, people, reason, technician, that, theory, you short-not long: term, syllable, hair, range, run, story short-not tall: none 4 When an adjective in a frozen noun phrase contributes no distinct meaning to the phrase (see footnote 1), it is excluded from consideration; such freezes should be found in the dictionary, and their identification in text is a separate problem. 5 The total number of sentences containing the target word that were extracted to yield 100 such adjectival instances of the target was 160 for hard, 444 for light, 124 for old, 278 for right, and 147 for short. Computational Linguistics Volume 21, Number 1 Table 1 Coverage and disambiguation error rates for target adjectives in lO0-sentence samples, using different indicator sets.</Paragraph> <Paragraph position="6"> The statistical procedure that was used to identify these nouns as indicators is described in detail in the Appendix. The number of significant indicators recovered is quite variable, ranging from none for the 'not soft' sense of hard, the 'not dark' sense of light, and the 'not tall' sense of short, to 13 for the 'not young' sense of old and 20 for the 'not wrong' sense of right.</Paragraph> <Paragraph position="7"> At this point, we had extracted a small set of statistically significant nouns that are projected to be indicators for adjective senses in the random samples. We then identified each instance in these samples in which a target adjective modified a projected indicator and tested the agreement of the target's sense with that which the noun was projected to indicate. This procedure tests the sense specificity of the projected indicators in the 100-sentence samples.</Paragraph> <Paragraph position="8"> The results of this test appear in Table 1 under the heading Indicator Nouns. The indicators do turn out to discriminate as projected between target adjective senses, and they do so with 100% reliability. Given this result, the set of indicator nouns can be treated as the basis for a disambiguation procedure. The extent of applicability of such a procedure can be inferred from the Coverage column, which records the proportion of target adjectives that modify projected indicator nouns. Overall coverage is 26.6% (see Table 1), rather low for a disambiguation procedure. The amount of co-occurrence data available for inference has had a substantial effect on coverage. Five of the ten senses are represented by fewer than 100 co-occurrence sentences each, and only one of these five yields any coverage at all. The other five senses are represented by more than 100 sentences each, and every one provides some coverage of the 100-sentence samples. There is therefore every reason to believe that coverage would increase with a larger base for inference. While we found a good semantic matching of adjective senses with the indicators that were recovered from the co-occurrence sentences, the indicator selection depended on an arbitrarily selected 5% level of statistical significance. We therefore investigated the dependence of performance on the chosen significance level. This dependence is highlighted most clearly by comparing the performance of John S. Justeson and Slava M. Katz Principled Disambiguation the statistically significant indicators, listed above, with that of the nouns from the subcorpora that are not significant as indicators of target sense. For this purpose, we therefore treated every noun from the co-occurrence sentences as an indicator of the sense which that noun is projected to favor in the sample sentences. The results are presented under All Nouns in Table 1. Coverage increased from 126 to 237 instances. The 111 newly covered instances are incorrectly assigned in only 7 cases; even when every noun from the co-occurrence sentences is treated as an indicator, reliability remains high (97.0%).</Paragraph> <Paragraph position="9"> The rather high reliability of even those nouns that are not statistically significant indicators of adjective sense suggests that in general text as well as in the co-occurrence sentences, most nouns are highly specific to the sense of their modifying adjectives. For example, not a single color word is a statistically significant indicator for the sense of light, although light blue, light brown, light gray, and light green all clearly use light in its 'not dark' sense. This example also illustrates that many of the individual nouns that we are treating as separate, independent cases actually manifest a smaller number of underlying semantic categories, e.g., color. Speakers' knowledge of language must somehow encode such cases, with patterns of use of individual nouns in relation to these adjectives emerging on the basis of that knowledge. A natural way to pursue the necessary revision is in terms of semantic attributes of these nouns, rather than in terms of the nouns themselves. We investigate this possibility, introspectively, in Section 4.4. This was already done to some extent when proper names were grouped together into classes.</Paragraph> <Paragraph position="10"> The modified noun is not always relevant to the process of disambiguation, and even when the noun is relevant, it is not always sufficient. The observed errors illustrate this (underlined nouns are from the projected indicators): &quot;I have something hard to speak,&quot; he remarked.</Paragraph> <Paragraph position="11"> A spatula is also used for lifting light pieces of food...</Paragraph> <Paragraph position="12"> They \[shells (of bullets)\] were small and light, but their turnip shape and radial fins made them difficult to conceal...</Paragraph> <Paragraph position="13"> The auctioneer.., auctioned off everything, obviously from the estate of an old, dying out family, in short order.</Paragraph> <Paragraph position="14"> Our spirit is so twisted, torn, because of self, out of its right center, God, and rooted in the flesh; the old life is so foul in the sight of God that no patchwork, no mere polishing up, no amount of varnish will do.</Paragraph> <Paragraph position="15"> The response to such old masters as Michelangelo, Rembrandt and Velasquez was and still is instant wonder and delight.</Paragraph> <Paragraph position="16"> The two-inch layer of fat that is attached to the inside of the seal's skin is left intact, and finally the whole hide is turned right side out.</Paragraph> <Paragraph position="17"> What are the sources of these errors? In the first sentence, something is not modified by hard at a deep syntactic level; it is instead to speak something that relates directly to hard, the surface modified noun being simply irrelevant (see Section 4.4.2). In the next case, the noun is not intrinsically irrelevant, but it turns out not to be useful; pieces is virtually empty semantically and can be modified by the target adjective in either sense (see Section 5.2). The remaining nouns are relevant. Family, life, and master are ambiguous, and once the ambiguity is resolved the sense of the modifying Computational Linguistics Volume 21, Number 1 adjective is reliably indicated; this issue is addressed in Section 5.1. Shell and side are also relevant to the sense of the adjective, but even when disambiguated themselves, further information about the context of light shells and right side is required before the sense of the adjective can be resolved. Section 5.2 addresses some of the contextual relations between adjectives and noun senses that sometimes resolve adjective sense when the intrinsic attributes of the noun sense do not.</Paragraph> </Section> <Section position="4" start_page="11" end_page="13" type="sub_section"> <SectionTitle> 4.4 Generalizing the Indicator Nouns </SectionTitle> <Paragraph position="0"> The mutual relevance of nouns and adjectives that permits sense disambiguation is concept specific rather than word specific. More than 40 nouns that are identifiable as indicators of adjective senses reflect a much smaller number of conceptual categories that directly relate to these senses.</Paragraph> <Paragraph position="1"> tually well-motivated basis for interpreting old, right, and short. With one exception (wine), the projected indicator nouns for the 'aged' sense of old--man, people, woman, you, he, person, lady, and proper names of people--refer to human beings. Expanding to include all nouns from the co-occurrence sentences that substitute young more than new for old, almost all added nouns continue to be for human beings, as well as certain pronouns (L we, you, he, she and me, us, her, him), to which animals, plants, and body parts are added. In the 100-sentence sample, all of the 10 'aged' instances of old that were not covered by the indicator nouns refer to members of these categories, 7 of them to human beings. Similarly, the correctness sense of right refers both to decisions and to decision-making entities, the latter primarily human; among 119 different nouns modified by right in the co-occurrence sentences, 14 of the nouns modified by 'not wrong' instances are +human, and all 55 nouns modified by 'not left' instances are -human. Finally, in the case of short, the vertical extent feature characterizing its 'not tall' sense is appropriate to relatively freestanding entities that are normally vertical, and humans are the most talked-about instances of such objects generally. There are differences among the different target adjectives in the appropriateness of the feature. In the case of old, it is a restricted version of the feature living thing; for right, of animate (people and animals); and for short, human beings happen to be a frequent instantiation of a verticality feature that is normally appropriate to woody plants and to relatively large land animals.</Paragraph> <Paragraph position="2"> The feature concrete is also very widely applicable. All indicators of the 'not soft' sense of hard are +concrete, so -concrete reliably indicates the 'not easy' sense of hard. Because hard in its 'not easy' sense also modifies concrete nouns syntactically, on the surface (though not semantically; see Section 5), +concrete does not as reliably indicate the 'not soft' sense of hard. Similarly, -concrete indicates the 'not wrong' senses of right, the 'not long' senses of short, and the 'gentle' subset of the 'not heavy' senses of light. It also indicates 'not new' senses of old, but in this case -concrete is simply a special case of -animate.</Paragraph> <Paragraph position="3"> Another widely relevant class of indicators are body parts. These indicate the 'not young' sense of old and the 'not long' sense of short. A substantial subset of them indicate the directional sense of right. This sense is associated with horizontally separated members of (mostly inherently) paired, repeated entities; it is appropriate to horizontally separated, paired body parts eyes, ears, thumbs, hands, wrists, arms, legs, feet, etc.--which constitute the majority of nouns, by text frequency, that are modified by the 'not left' sense of right. For noninherently paired entities, more complex phrasings such as on the right or rightmost are used instead (also on the left or leflmost). Body parts are less well represented in the co-occurrence sentences for hard; those that occur John S. Justeson and Slava M. Katz Principled Disambiguation (shell, palate, tissue) are sense specific for 'not soft,' being specific cases of +concrete and subject to the reservations on +concrete indicator nouns noted above.</Paragraph> <Paragraph position="4"> Other semantic features are more restricted to individual adjective senses. The attribute +color disambiguates about half of the 'not dark' instances of light. Lengthrelated ('not long') senses of short are indicated by nouns that are +time period (term, period, day, duration, minute, month, night, time, weekend, in the co-occurrence sentences), but this attribute is subsumable under -concrete. Text/utterance type (e.g., story, note, book, manuscript, monolog, phrase, speech, stanza), though largely subsumable under -concrete, often have +concrete realizations (as for book, note, manuscript).</Paragraph> <Paragraph position="5"> Some highly specific attributes are clearly relevant; for example, +military entity (cruiser, carrier, gun, arms, armor, dragoon, flak, machine gun, missile) indicates the 'not heavy' sense of light, and +mental (answer, decision, reason, theory, argument, assumption, conclusion, conviction, guess, method, notion, opinion, policy, prediction, proposition, question) indicates 'not wrong' senses of right. Until many more adjectives have been investigated, we avoid introducing overly specific features whose range, applicability, and definition may be unclear. These are perhaps subsumable under more general attributes. This is the case for +mental, a special case of a highly reliable and more general indicator, -concrete (see Section 5.2 concerning the more complex case of military entity and the relation of text type, which we do use, to the time period attribute).</Paragraph> <Paragraph position="6"> In some cases, semantic features such as those discussed above can be used straightforwardly as sense indicators, just as nouns were. For example, a +human noun indicates the 'not tall' sense of short; a -concrete noun indicates a 'not long' sense of short. In other cases, however, the move from specific nouns to semantic features as sense indicators necessitates the formulation of more specific rules for using them. For example, -concrete nouns indicate a 'not heavy' sense of light, except that -concrete nouns that are +color indicate its 'not dark' sense. This requires a formulation using either feature combinations or rule ordering. We can implement this by first attempting to apply a rule +color ~ 'not dark' and then attempting to apply a rule -concrete ~ 'not heavy', to any unresolved cases (Table 2). More complex rules can be expected to be required in other cases.</Paragraph> <Paragraph position="7"> We do not propose, in general, to extract automatically either semantic generalizations like those discussed above, or the rules that use them. Informed introspective analysis, aided by a perusal of corpora, seems a surer way toward rule-based formulations. Human analysis and understanding are simply richer than the mechanical statistical tools and data sources presently available for arriving at such rules.</Paragraph> <Paragraph position="8"> evant and indicator nouns are readily recovered, Section 4.4.1 shows that coverage can be increased by exploiting specific indicator nouns in order to infer or to extract automatically general semantic attributes of nouns. For some of the indicators, however, generalization properly takes another course, leading not to semantic but to syntactic cues for sense identification. For example, predicate adjective usage indicates the correctness sense of right, which is clearly manifested throughout the APHB Corpus.</Paragraph> <Paragraph position="9"> That's not quite right.</Paragraph> <Paragraph position="10"> Much thought had gone into that costume, and it seemed just right for a poor man's wife.</Paragraph> <Paragraph position="11"> We refer to these as cases of a predicative indicator feature.</Paragraph> <Paragraph position="12"> The most prominent example in our data is generalization from the non-anaphoric it indicator for the 'not easy' sense of hard, which is also applicable for the 'not wrong' Computational Linguistics Volume 21, Number 1 sense of right. This indicator is found in statements of the form It BE ADJ + infinitival clause, where BE is a form of the verb to be. Auxiliary verbs, adverbials, or negation occurs optionally in these statements, and the infinitival clause need not follow immediately. It is often deleted, and in such cases an anaphoric pronoun may replace the non-anaPhoric it, resolving to a preceding or following clause. Also, the verb BE may be deleted and the entire construction subordinated to a higher verb such as seems or becomes. We refer to these as cases of an infinitival indicator feature.</Paragraph> <Paragraph position="13"> It wasn't hard to find Marietta Price.</Paragraph> <Paragraph position="14"> Somehow it has never been hard for me to believe in Francis&quot; wounds...</Paragraph> <Paragraph position="15"> It's sometimes hard for a motorist to pass a young fellow standing on the edge of a highway.</Paragraph> <Paragraph position="16"> Since he's doing this for his physical welfare, it wouldn't be right of me to let him be bothered.</Paragraph> <Paragraph position="17"> A result of this pattern is that almost any verb will look like an indicator for these same senses of hard and right. 6 This appearance, however, is spurious. The proper generalization is simply the syntactic construction, including its variants in which the non-anaphoric it does not occur. The variants include those in which the entire infinitival clause, or a gerundive phrase based on it, serves as the subject of the main clause, with hard or right as predicate adjective, But becoming more independent is hard for many children.</Paragraph> <Paragraph position="18"> and those in which a noun object from the infinitival clause is promoted to serve as subject of the verb of being, in place of it.</Paragraph> <Paragraph position="19"> Later, Mama may have regretted being married, because Papa was so hard to understand.</Paragraph> <Paragraph position="20"> Her energy was tremendous, her scruples hard to find.</Paragraph> <Paragraph position="21"> Since the adjective is characterizing an action or state of affairs, these cases can be subsumed under the +activity or -concrete semantic attributes discussed in Section 4.4.1 as indicators of these senses of hard and right. Even as a premodifier of a noun, the adjectives in this construction often relate semantically to the verb phrase, e.g., This is a hard program to carry out.</Paragraph> <Paragraph position="22"> What is hard is the carrying out of the program, not the program itself. Once again, it is the syntactic construction, and not the modified noun, that is the relevant indicator. These considerations help us to refine our use of the adjective-noun relation itself and to put it on a firmer linguistic footing. The adjective-noun relation is directly pertinent to semantic attributes of both the adjective and the noun only when there is a deep syntactic relation between them. In the case of the infinitival and related constructions, no such relation holds; the noun modified by the adjective at the surface level</Paragraph> </Section> </Section> <Section position="7" start_page="13" end_page="14" type="metho"> <SectionTitle> 6 A minority of verbs with a specific relation to the opposite sense do exist, e.g., feel relates to the 'not </SectionTitle> <Paragraph position="0"> soft' sense of hard. Such verbs relate to the alternative sense only when they are outside of the infinitival constructions.</Paragraph> <Paragraph position="1"> fore requires a determination that the adjective modifies the noun at a deep syntactic level. It is therefore important to take into account the infinitival construction prior to disambiguating any adjective--even those for which it does not constitute an indicator. The last two columns of Table 1 present the results of adjective disambiguation by a combination of syntactic and semantic indicator attributes. The disambiguating rules we used are given in Table 2. The syntactic indicator attributes, predicative and infinitival, were applied first. Afterward, if a target adjective sense was not resolved, semantic indicator attributes were applied; no individual indicator nouns were used. The semantic attributes that were applied were animate, body part, color, concrete, human, and text type; Church and Hanks (1989) had pointed to two of these attributes, person and body part (also time, previously mentioned above) in a seemingly casual listing of just five attributes potentially useful for describing the lexico-syntactic regularities of noun-verb relations.</Paragraph> <Paragraph position="2"> Table 1 shows that these few, general attributes cover almost three-quarters of all instances of the target adjectives. Disambiguation by these syntactic and semantic attributes is effectively as reliable as disambiguation using significant indicator nouns: having three apparent errors in disambiguation is not significantly worse than the errorless performance of the significant indicator nouns in the 100-sentence samples.</Paragraph> <Paragraph position="3"> In fact, under a deeper analysis, these three cases are consistent with the pertinent attributes and should not be treated as errors at all. In one sentence, In contrast to his rangy sons, he was a short, heavy, oaken-barrel sort of man.</Paragraph> <Paragraph position="4"> short modifies sort (-concrete) and was thus assigned the sense 'not long.' However, it is actually relevant not to the head of the noun phrase, sort, but rather to man (+animate); so treated, short would be correctly assigned to 'not tall.' More complex are the two instances of old wine. In the APHB Corpus at large, the new~old contrast applied to wine relates chiefly to contexts of production of the wine or of the introduction of a type of wine. The young~old contrast relates instead to the maturation of some wines, or more generally, to the developmental phases through which wine passes while aging over a period of years. It is a cultural (and thus semantic) fact that wines and other nonanimate entities that undergo developmental changes and pass through maturational stages are treated as living things. Since the two instances of wine in the 100-sentence samples are of this sort, their old modifiers are properly assigned to 'not young'; we assigned them to 'not new' under a literal interpretation of -animate.</Paragraph> <Paragraph position="5"> The rules in Table 2 can be easily implemented. The approach presupposes that the natural language processing system within which it is applied includes a reliable, wide-coverage parser to determine the noun phrase modified by an adjective and the head of that noun phrase. The lexical database used by this parser must include semantic attribute tags. Most of those used in this paper are already present in some available machine-readable dictionaries, such as the Longman Dictionary of Contemporary English. Such a disambiguation procedure is capable of disambiguating, with very high reliability, about three-quarters of the 100-sentence sample instances of the target adjectives we have investigated.</Paragraph> </Section> <Section position="8" start_page="14" end_page="20" type="metho"> <SectionTitle> 5. Further Considerations </SectionTitle> <Paragraph position="0"> Although the sense clues discussed so far can be readily implemented as a disambiguation procedure, about a quarter of all instances of the adjectives under study were not covered by the rules presented in Table 2. This section addresses these un- null 2. -concrete ~ 'not easy' +concrete ~ 'not soft' 1. +color ~ 'not dark' 2. -concrete ~ 'not heavy' 1. -animate ~ 'not new' +animate ~ 'not young' 1. +predicative ~ 'not wrong' +infinitival ~ 'not wrong' 2. -concrete ~ 'not wrong' +human ~ 'not wrong' +body part ~ 'not left' 1. +human ~ 'not tall' covered cases. Some are readily characterized in terms of the general approach of the previous section; others are more complex. The following discussion treats the kinds of properties that systematically relate adjective senses to other features of the sentences in which they occur. Unlike the previous section, it does not point to any automated procedure to take advantage of these properties, or to the role they might play in some more encompassing procedure, and it uses coverage and reliability as measures of the actual association of adjective senses with other constructs, irrespective of their recoverability from raw text. Thus, this section is concerned with the nature of underlying relations--not with formulating a disambiguation procedure.</Paragraph> <Section position="1" start_page="14" end_page="17" type="sub_section"> <SectionTitle> 5.1 Indicator Noun Sense Attributes </SectionTitle> <Paragraph position="0"> We have found that a substantial proportion of adjectives can be disambiguated by the nouns they modify, largely on the basis of general semantic attributes characterizing those nouns. These attributes, being semantic, must relate in fact to noun senses and not to nouns per se. This issue is finessed, to some extent, in the projected indicator nouns and thus in our application of attributes based on them. Some attributes happen to apply to all senses of a given noun. For example, in the 100-sentence samples, course disambiguates short, though once it is used for 'path' and once for 'class,' because both senses are -concrete. Some indicator nouns were extracted, not because the attribute applies to all senses of these nouns, but because these nouns are used far more often in senses to which an indicator attribute applies than in those to which it does not apply.</Paragraph> <Paragraph position="1"> For example, people shows a statistically significant tendency to be associated with the 'aged' ('not young') senses of old (when people is the plural of person), as judged from the co-occurrence sentences, although one instance of the 'of long standing' ('not new') senses of old (when people meant 'ethnic group') was also found.</Paragraph> <Paragraph position="2"> John S. Justeson and Slava M. Katz Principled Disambiguation In many instances in the 100-sentence samples, the noun modified by a target adjective was ambiguous with respect to one of the indicator attributes: an indicator attribute did characterize some of the noun's common senses, but not others. For example, the noun side is projected to occur equally often with each sense of right ('not left' 49.9%, 'not wrong' 50.1%). However, this noun has two broad classes of meanings: one refers to commitments on issues and is -concrete; the other refers to flanks and is +concrete. As expected on the basis of this semantic attribute, right usually means 'not left' when it modifies side in its (locational) sense 'flank,' but virtually always means 'not wrong' when modifying side in its commitment sense. The sense of side is therefore a more reliable indicator of the sense of right than is the noun itself.</Paragraph> <Paragraph position="3"> If these nouns are disambiguated with respect to the relevant attribute, reliability can be increased, as in the case of right side. Coverage will increase as well. Some nouns have two or more common senses that disagree in the value of relevant attributes and thus were not recovered as indicator nouns; their senses might well be reliable indicator features. Disagreements in the value of a semantic attribute for a given noun can even be systematic. Any noun N with sense S can be used to mean 'a type of S,' as with family doctor in Swedes lament the almost total disappearance of the old family doctor.</Paragraph> <Paragraph position="4"> When types are construed as -concrete, as when referring to roles, such uses are specific to 'not new' senses of old (and to 'not wrong' senses of right). Thus, any noun or semantic attribute that is associated with the alternative senses of these adjectives would be wrongly interpreted when a 'type of S' usage of the noun is not recognized.</Paragraph> <Paragraph position="5"> Another widely pertinent example is the more complex ambiguity in the reference of modified nouns for roles or relationships. A role noun almost always refers to an individual (+animate) who stands in that relationship to another, as in all the example sentences cited below; for example, when the nuns, new and old, filed out of the cloister, it was a set of persons and not of relationships who did so. The adjective, however, may apply to that individual (a +animate noun sense) or to the role itself (a -animate noun sense). Thus, the adjective old may apply either to the relationship or to the role designated by doctor, friend, empress, and nun, with old having the sense 'former' or 'of long standing': ... I was with old friends; I had made new friends; and that night I think that I was lonelier than ever before.</Paragraph> <Paragraph position="6"> It was only to be expected that the lords and ladies of the court would compare the first wife and the second, the old empress and the new.., all in favor of the old.</Paragraph> <Paragraph position="7"> A prayer, the Bishop's blessing--and the nuns, new and old, filed out to the cloister.</Paragraph> <Paragraph position="8"> or to a person having that relationship or role, with old having the sense 'aged': *.. he rang to six friends, not too young, not too old, and explained that he'd have to postpone their dinner.</Paragraph> <Paragraph position="9"> The old doctor and the young doctor rode in silence for two miles and indulged in their memories* On the contrary, these nuns, young and old, were invariably cheerful and happy, almost gay and full of childish fun and laughter...</Paragraph> <Paragraph position="10"> Computational Linguistics Volume 21, Number 1 There is an inherent ambiguity concerning the relation of the adjective old to its noun: the referent of the noun is an individual (which is +animate), but it is an associated noun sense to which the adjective applies (which may be +animate or -animate) that strictly determines the sense of old. In the 100-sentence samples, when old modifies a role noun, it always applies in its 'aged' sense to the individual and in its 'former' sense to the role. Some role/relationship nouns are used overwhelmingly in their role senses (as with friend) or in their personal senses (as with doctor). Otherwise, inferring the correct sense for old involves a resolution of the function of the noun. For example, an old forest is 'not new' if it has existed for a great period of time and 'not young' if it is in an advanced stage of development in the life cycle of forests (cf., the discussion of wine in Section 4.4.2).</Paragraph> <Paragraph position="11"> This semantic ambiguity in the noun sense to which the adjective applies can therefore be resolved by the same rules formulated for unambiguous cases, once the relevant noun sense is identified. How to access the relevant noun sense is an unsolved problem: the noun's direct referent is an individual, whereas the semantic structure entailed by the noun is a semantic network, and the adjective may apply to the network's noun sense nodes rather than to the noun referent itself. The utility and elegance of such semantic representations is suggested by linguistic discussions on lexical semantics. They have been used with notable success by Fillmore and Atkins (1991), who exploit the intricacies of such networks in a now-classic account of the semantics of risk, with different nodes of the network providing the locus of what might be distilled as the word's distinct senses. Similar network representations are adopted and implemented in restricted domains in several computational models (e.g., Sowa 1986).</Paragraph> <Paragraph position="12"> The semantics of noun senses therefore relate more specifically and directly to adjective senses than do nouns themselves; in fact, 38 (30%) of the 125 cases not covered by the rules of Table 2 are resolved when these broader semantic structures are used. In most of these cases, noun senses themselves supplied the attributes used by the rules of Table 2 to disambiguate adjectives. In other cases, such as role nouns, with more complex semantic structures, we are able to resolve the semantic relation of adjective and noun, but this ability cannot be captured in rules as simple as those of Table 2.</Paragraph> </Section> <Section position="2" start_page="17" end_page="20" type="sub_section"> <SectionTitle> 5.2 Other Indicators of Adjective Senses </SectionTitle> <Paragraph position="0"> Section 4 showed that indicator nouns and, in particular, certain of their semantic features are quite reliable as bases for interpreting the meanings of the adjectives that modify them. In some cases, however, nouns provided very little assistance when the pertinent semantic and syntactic features do not apply, the same noun is often simply consistent with alternative senses. This was systematically true for relationship nouns modified by old. Similarly, the adjective light can refer either to weight or to color in modifying most concrete nouns.</Paragraph> <Paragraph position="1"> In these cases, disambiguation involves words other than the noun that the target adjective modifies, standing in other syntactic relations to the target. The effectiveness of one such alternative has already been demonstrated--the special case of antonymic adjectives. In the special constructions discussed in Section 3 and, in particular, when they modify the same noun, they disambiguate one another with almost perfect reliability. Consider, for example, the sentence A piece will seldom bake uniformly, even with the most loving attention--that is, it will vary from light to very dark...</Paragraph> <Paragraph position="2"> The target adjective light modifies the pronoun it, which refers anaphorically back to John S. Justeson and Slava M. Katz Principled Disambiguation piece (of food being baked). Light pieces of food may be either 'not dark' or 'not heavy,' so the noun provides no substantial aid to interpretation. However, the phrase from light to dark secures the intended sense of light.</Paragraph> <Paragraph position="3"> Verb senses can relate systematically to adjective senses, because adjectives often designate attributes pertinent to the application of the verbal action to/by the referent of the modified object/subject noun. Verbs are therefore useful to the interpretation of adjectives modifying subject or object nouns. Returning to the difficult case of light, one of the 7 sentences in which an error was made when all nouns were treated as indicators (see Section 4.3) is A spatula is also used for lifting light pieces of food...</Paragraph> <Paragraph position="4"> In this sentence, the head noun pieces is irrelevant, essentially empty semantically. The critical noun is food, but it is not a directly usable indicator; light food may be either 'not heavy,' as in this sentence, or 'not dark,' as in the previous example. It is instead the verb lifting that provides the best sentence-internal indication of the 'weight' sense of light in the example under consideration. The 5 APHB sentences that refer to the lifting of a light object all involve the 'not heavy' sense of light. This is not a logical requirement--both dark and heavy objects are also said to be lifted. But the weight of an object is intrinsically relevant and its color irrelevant to the lifting of ~,hat object; a reference to the lifting of a light N in the 'not dark' sense is likely to be misconstrued unless additional cues to interpretation are provided. Similar results are found for semantically similar verbs. Thus, carry disambiguates light in Furniture movers, for example, carry light objects in their hands.</Paragraph> <Paragraph position="5"> whereas the modified noun is of no help. Accordingly, physically supports is a semantic attribute of some indicator verbs for the 'not heavy' sense of light.</Paragraph> <Paragraph position="6"> In some cases when a noun or even a noun sense is consistent with more than one sense of the target adjective that modifies it, a default target sense may be reliably inferred so long as there is no strong counter-evidence in the immediate context. Old doctor, for example, means 'aged doctor' in 28 of 30 instances in our corpus. The other 2 cases are both for old family doctor. In one, the sentence itself makes it clear that a generic 'type of doctor' sense was intended (see Section 5.1). Similarly, old means 'former' in the sentence I know that the old family doctor, Dr. Schlomm, always told Manya she could be stabilized on medication, that she could be kept under control.</Paragraph> <Paragraph position="7"> as shown by the immediately following sentence: So did her present doctor.</Paragraph> <Paragraph position="8"> A more complex example of default inference is provided by right as a modifier of side. The commitment sense of side strongly favors the correctness sense of right, whereas the locational senses of side favor the directional senses of right. However, even with the locational sense of side, 'not wrong' is not an anomalous usage. Compare, for example, the following sentences from the APHB Corpus: They were hiding behind the big oak on the left side of the road.</Paragraph> <Paragraph position="9"> Computational Linguistics Volume 21, Number 1 &quot;Can't you see you're on the wrong side of the road?&quot; Hoover leaped from his car and ran to the left side of the gangster's car.</Paragraph> <Paragraph position="10"> Zaza still stood in the road, on the wrong side of the car.</Paragraph> <Paragraph position="11"> In the face of such examples, it becomes difficult to interpret the adjective in such sentences as But the car, now on the right \[not left\] side of the road, was too late to veer away from the second tire...</Paragraph> <Paragraph position="12"> He was on the right \[not wrong\] side of the screen, he had an excellent day's work behind him, and in two minutes&quot; time he would hear Bing Crosby sing.</Paragraph> <Paragraph position="13"> except with respect to the broader discourse context. In our data, locational senses of side always involve the directional sense of right in right side of unless there is decisive evidence to the contrary in the same sentence or in the immediately surrounding discourse. In many of the directional sense uses, we find no overt clue within the sentence or the immediate discourse to determine the sense; it appears to be simply the assumed interpretation when no specific information contradicts it. In contrast, for each of the (6 out of 45) instances in which a correctness sense of right modifies a locational sense of side in right side of, there is something explicit in the near context, usually in the same sentence. For example, the ambiguous case of the right side of the screen, above, is resolved by a preceding sentence (two short sentences intervene): Across the centre of the hall hung a screen, and on this screen was being projected a motion picture; half the men had to see the picture back to front, because they had to look at it from the back \[the wrong side\] of the screen, but nobody minded that very much. The directional sense of right cannot be construed as a general default, since the correctness sense is far more common overall. Evidently, the locational sense of side of is so powerful a semantic indicator for the directional sense of right that people do not use right side of in other senses without providing substantial countervaling evidence for the sense. Relative to a given indicator noun, then, it makes sense to think of adjective disambiguation in terms of default interpretations.</Paragraph> <Paragraph position="14"> Some noun-based disambiguation of adjectives involves the noun's functionality rather than its intrinsic semantic attributes; many such nouns relate to relevant attributes of indicator verbs. The adjective light, when modifying a +concrete noun, is a case in point. Both weight and color characterize all +concrete entities. In fact, however, we can reliably determine the sense of light in a number of these cases. Three nouns in the co-occurrence sentences emerged as significant indicators for the 'not heavy' sense of light--cruiser, load, and harness. It is the weight and not the color of a load that is functionally relevant; the thickness and thus weight of a harness that bears on the speed and load-bearing potential of the draught animals fitted with it; and the heaviness of a vessel that is relevant to the speed, ease of handling, load-bearing potential, and imperviousness to damage that is pertinent to military cruisers. In fact, if it were necessary to specify such entities as being light in color, we would expect that their functional specificity for lightness in weight would lead to the use of a more specific qualifier, such as light-colored, rather than simply light. Semantic attributes such as carried things would characterize nouns such as load, e.g., burden, cargo, or freight, and load-bearing equipment or load-relevant equipment would characterize nouns such as John S. Justeson and Slava M. Katz Principled Disambiguation harness and cruiser. In the sample of sentences containing light, the following might be subsumed under such attributes: aircraft, brigade, car, cart, defense, guard, horse, industry, package, shell, tank, and weight. Some of these, such as shell and tank, have meanings to which the load-bearing issue is not relevant, though in the case of tank the application of the adjective light does appear to restrict its referent to the military vehicle. Others, such as car, involve issues of fashion and decoration to which color and thus darkness is potentially relevant as well, although the 5 instances of light car(s) in our corpus do refer to weight (with dark car(s) referring to a darkened interior). But suitably constrained either to subsets in which decoration is not a functional value (e.g., military~industrial equipment) or by treating feature combinations that include, e.g., -decorative relevance, it would be possible if not ideal to handle such nouns in terms of attribute values. Thus, some nouns can be disambiguated by relatively narrowly defined semantic classes, such as military/industrial equipment, and with high reliability, leading to something close to lexicalized noun phrases, e.g., light cruiser or light industry. But it is in fact the functional relevance of heaviness versus darkness in the context of its use that is actually involved.</Paragraph> <Paragraph position="15"> A more complex example is provided by those indicators for the 'not long' sense of short that are types of texts or utterances--book, manuscript, monologue, note, phrase, poem, speech, stanza, story, and syllable. These, like +time period, are largely subsumable under the -concrete feature, but there are also +concrete instances of some of these nouns, such as book, that still select the 'not long' sense of short. In these instances, it is not a physical dimension of the item that is short, and reference to such dimensions in the case of book relates instead to the 'not tall' sense of short. Superficially, this might support the pertinence of a special attribute, textual, for disambiguating short. However, the 'not long' characterization of shortness of texts refers explicitly or implicitly to the duration of the performance (e.g., reading or reciting) of the text. Accordingly, it is the time period attribute that would appear to be involved in this case---an attribute of activities that constitute the typical use of texts, not an attribute of texts themselves. The relationship involved in this case is comParable to that discussed by Pustejovsky and Boguraev (1993), in which a single sense of fast relates speed of vehicle motion in both fast car and fast highway via the qualia structure of lexical entries for highway and car. Accordingly, although most instances of nouns for text types can disambiguate short by being -concrete, the principled basis for disambiguating the adjective entails a more complex type of inference than simple characterization of semantic attributes of the modified noun itself.</Paragraph> </Section> </Section> class="xml-element"></Paper>