Subsections

• Introduction
• Classification of adjectival polymorphism
• Representation of the properties

   
Adjectives

   
Introduction

Adjectives have not much been studied in traditional lexical semantics compared to the large amount of work devoted to verbs and to nouns. They nevertheless present an interesting polymorphic behaviour. Syntactically, they can appear in different positions in the sentence, as modifier of the noun (a sad book) or complement of a copular verb like be (this book is sad). Semantically, adjectives, more than other categories, are able to take different meanings depending on their context (for example difficult in a difficult child, a difficult book, a difficult exam or fast in a fast car, a fast motorway, a fast procedure, etc.) ([Mar83], [Lah89], etc.). As senses are only restricted by the number of possible contexts, it is questionnable if they can be enumerated. Even more, richer representations and compositional mechanisms seem to be required ([Bou97].

In the following, we give first a general overview of this polymorphism. We then examine how they are represented in two models: relational (WordNet 3.4) and generative (Generative Lexicon 2.8.3).

   
Classification of adjectival polymorphism

Adjectives differ in many ways. We will examine their polymorphism from three different perspectives: syntactic, semantic and ontological.

   
Syntactic classes

Syntactically, adjectives can be classified with respect to three features: function, complementation and alternation.

1.

Function: adjectives can appear in attributive position, as noun modifiers inside NP (32), or in predicative position as a complement of a verb like be, seem, consider, etc. (33).

(32)

  A happy person

(33)

  They are happy, they consider him happy, he seems happy, etc.

This criteria allows us to distinguish three different types of adjectives: predicative-only (34) and attributive-only (35) for adjectives that are only used in one position, or central for those used both predicatively and attributively, as tall in (36) (Quirk et al., 1994, for example).

(34)

  *Afraid people, people are afraid

(35)

  The atomic scientist, *the scientist is atomic

(36)

  The tall man, the man is tall

When attributive, adjectives can be both postnominal and prenominal (37a), even if the postnominal position is less common in English [Sad93]. But there are restrictions: an adjective like former cannot be postnominal (37b) and some adjectives appear only after the noun (37c).

(37)

a.

  navigable rivers, rivers navigable

b.

  former architect, *architect former

c.

  *aforethought malice, malice aforethought

2.

Complementation: As verbs, adjectives differ in terms of their argument structure. Many adjectives accept no complement at all (for example, belgian, red, etc.). Those that accept complements can be subclassified as follows:

• the type of the complement they subcategorize, i.e. prepositional (38a) or clausal (VP (38b) or sentential, S (38c));

  (38)

  a.

    I'm proud of you

  b.

    I'm sad to leave

  c.

    It is possible that they leave

• whether the complement is optional or not (I'm desirous to leave, *I'm desirous vs I'm sad to leave, I'm sad);

• for prepositional complements, the preposition that marks the NP (for example capable of, skillfull at, absent from, etc.).

3.

Alternations: As for verbs, adjectives enter into alternations.

• Among adjectives that take clausal complement, two subclasses can be distinguished, according to whether this complement may or may not be realized as the subject. It is common to call object embedding adjectives whose complements cannot be realized as subject (39) and subject embedding those which can take a clausal subject (40) ([Pic78], [Ven68], [Arn89], [Dix91], [Sil77].

  (39)

   

  a.

  ii.

  I'm sad to leave

  ii.

  To leave is sad for me

  b.

  ii.

  They are certain to leave

  ii.

  To leave is certain for them

  c.

  ii.

  Sam was brave to leave

  ii.

  To leave was brave of Sam

  (40)

   

  a.

  I'm eager to come

  b.

  *To come is eager

  The adjectives that allow their subject to be clausal can be further classified depending on what preposition marks the accompanying nominal complement, as in (41) [Arn89], [Sil77]. This allows [Arn89] to distinguish four classes of adjectives: S-only and S+toNP adjectives indicate some perception of the modality of the clausal clause; S+ofNP adjectives give an evaluation of an individual, on the presupposition that he is responsible for the state of affairs described in the proposition. Finally, S+forNP adjectives characterize directly a state of affaires, but may also indicate an experiencer.

  (41)

   

  a.

  That they left is possible (S-only)

  b.

  That they left is clear to Sam (S+toNP)

  c.

  That he left was brave of him (S+ofNP)

  d.

  To ignore pollution is dangerous for the country (S+forNP)

• It-extraposition: All adjectives that are suject-embedding allow the it-extraposition (42).

  (42)

   

  a.

  It is possible that they left

  b.

  It is clear to Sam that hey left

  c.

  It was brave of him that he left

  d.

  It is dangerous for the country to ignore pollution

• Tough-construction: some s+forNP adjectives allow the tough-construction (43b), where the subject of the adjective is understood as filling a non-subject position in the complement of the adjective (see for example [Arn89] for an overview).

  (43)

  a.

  It is difficult to support this proposal

  b.

   This proposal is difficult to support

   
Logical classes

Semantically, adjectives can belong to three different classes, which differ in their logical behaviour in the following way ([Chi90], [Arn89], [Par90], pp. 43-44).

1.

An adjectives (ADJ) is said absolute (or intersective, predicative, etc.) if (44a) implies (44b) and (44c). These adjectives are standardly analyzed as predicates: they denote properties and the denotation of the adjectif-noun construction is the intersection of the denotation of the ADJ and the N.

(44)

a.

  this is a red (ADJ) table (N)

b.

  $\rightarrow$ this individual is a N

c.

  $\rightarrow$ this individual is ADJ

Typical examples of this category are adjectives wich denote:

i.

a shape: hexagonal

ii.

a social group or a nationality: communist, belgian, etc.

iii.

a color

2.

An adjective is property-modifying (or non-intersective, operators, etc.) if (45a) does not imply (45b), nor often (45c): a former architect is not an architect, nor former. These adjectives have been analyzed as operators: they denote a function from properties to properties. Thus, for example, former in (45a) takes the denotation of architect to the set of individuals who used to be architect.

(45)

a.

  this is a former (ADJ) architect (N)

b.

  / $\rightarrow$ this individual is a N

c.

  / $\rightarrow$ this individual is ADJ

Property-modifying adjectives include: nominal (or relational) adjectives (polar bear, atomic scientist, etc. Cf. [Lev78], manner (or adverbial) adjectives (a poor liar, a fast car), emotive (a poor man) and modals, i.e. all adjectives which are related to adverbs, quantifiers or determiners (a feeble excuse, the specific reason, a fake nose, etc.).

3.

An adjective is relative (or scalar) if (46a) implies (46b), but not (46c); a big mouse, for example, is not a big animal. As absolute adjectives, they characterize the individual described by the noun (46b), but, unlike them, it is relative to some norm or standard of comparison: a big mouse is big for an F, where F is supplied by the context (46d). As they share properties with absolute and relative adjectives, they have been analyzed both as predicates and operators ([Par90], p. 44): on the predicative treatment, x is a clever N for example, means therefore x is an N & x is clever for an F and on the operator treatment, it means clever(x is an N that is F).

(46)

a.

  this is a big mouse

b.

  $\rightarrow$ this individual is a N

c.

  / $\rightarrow$ this individual is Adj

d.

  $\rightarrow$ this individual is Adj for a F

   
Other semantic classes

The adjectives can also be classified with respect to other semantic features [Qui94], as:

1.

Aspect: an adjective can be stage-level (if it expresses a temporary or accidental property) as in (47) or individual-level (in case of a generic, permanent or inherent property) (48) [Car77], [Car95].

(47)

  drunk, available , etc.

(48)

  clever, tall, etc.

2.

Gradation: an adjective can be gradable or not.

   
Adjective taxonomies

Adjective taxonomies classify adjectives in the different semantic categories they can express (see [Ras95] for a good introduction). [Dix91] is one of the most representative. He classifies adjectives as the following:

(49)

1.

DIMENSION: big, short, etc.

2.

PHYSICAL PROPERTY: strong, ill, etc.

3.

SPEED: fast, quick, etc.

4.

AGE: new, old, etc.

5.

COLOR: red, black, etc.

6.

VALUE: good, bad, etc.

7.

DIFFICULTY: easy, difficult, etc.

8.

QUALIFICATION: DEFINITE (probable), POSSIBLE (possible), USUAL (usual), LIKELY (likely), SURE (sure), CORRECT (appropriate)

9.

HUMAN PROPENSITY: FOND (fond), ANGRY (angry, jealous), HAPPY (anxious, happy), UNSURE (certain), EAGER (eager, ready), CLEVER (clever, stupid, generous)

10.

SIMILARITY: similar, different, etc.

For each class, Dixon specifies the syntactic behaviour of each adjective, as follows: ``EAGER takes an NP or a THAT or MODAL (FOR) TO complement, e.g. I'm eager for the fray, I'm eager that Mary should go, I'm eager (for Mary) to go. Ready may only take an NP or a Modal (FOR) TO clause (not a THAT complement) while willing must take a THAT or Modal (FOR) TO clause, i.e. it cannot be followed by proposition plus NP.'' ([Dix91]. p. 83).

These classifications have a descriptive value, but none of these types of taxonomies have been applied in practical applications (ch. [Ras95], p. 10). They pose two main problems: first, they reveal little about the functional and relational properties of the adjective; secondly, they don't explain why adjectives share or do not share some syntactic behaviour.

   
Representation of the properties

   
Introduction

The former section identified the different properties of adjectives. This one examines how they are represented and generalized in two major models: WordNet and Generative Lexicon.

   
Semantic network, WordNet

In WordNet ([Gro90] 3.4), adjectives are divided in two main classes, which are said to account for the majority of adjectives: ascriptive wich are considered to ascribe a value of an attribute to a noun and nonascriptive which are similar to nouns used as modifiers.

Ascriptive adjectives are organized in terms of antonymy and synonymy, as in (50):

(50)

 {DRY, WET1,! anhydrous,& arid,& ...}
{anhydrous, dry1, & }
{arid, waterless,dry1, & }
{dehydrated, desiccated, parched, dry1, & }
{dried, dry1, & }
...

Non-ascriptive ones are considered as stylistic variants of modifying nouns and are cross-referenced to the noun files. For example, the entry (51) indicates that astral and stellar have the meaning of pertaining to a star or stars

(51)

  {star | astral, stellar}

Gradation is not indicated in WordNet 3.4 because it is not often lexicalized in English. Restrictions on syntactic position (for prenominal-only and postnominal-only adjectives) are directly encoded in the the word, as they cannot be infered from the head word in the cluster (52).

(52)

  AWAKE(p), ASPEEP(p),! alert, & ALERT, ...

WordNet does not say anything about the way senses are related: adjectives have as much senses as synsets. Moreover, it does not provide the means to predict grammatical properties from the representation (complementation, alternations, selective restriction). These two features distinguish the relational approach of WordNet from a Generative approach, like Generative Lexicon.

   
Generative Lexicon

Generative Lexicon, [Pus95a] focusses on the two aspects neglected in WordNet : (1) how the different adjectival senses are related and how they can be derived compositionaly from the representations of the noun and the adjective [Bou97] and (2) the syntax-semantics interface. In this theory, the adjectival polymorphism is explained by richer representations of adjectives and nouns (the qualia structure) and the way they combine together.

Take as an example the ambiguity of the French adjective vieux (old) in un vieux marin (an old sailor) which can be both relative (aged) and property modifying (with the meaning who has this capacity for a long time, without being necessarily aged). It can be explained in the following way (cf. [Bou97] for more details).

1.

Semantics of the noun: nouns to which adjectives apply have complex representations, which define the different predicates necessary for the definition of the word ([Bus96a]); a sailor, for example, is defined as somebody who has the capacity of sailing, i.e. as the conjunction of three types: human, state (have the capacity to) and event (to sail).

2.

Semantics of the adjective: the semantics of vieux indicates that this adjective has two functional types: it can apply to an individual (un vieil homme) or a state (une vieille amitié).

3.

Composition: As vieux has two different functional types and asmarin is defined by the conjunction of these types, it can apply to both of them, giving rise to the ambiguity of the adjective-noun construction : in one sense, the adjective applies to the type human denoted by marin (un vieux marin is then understood as an old individual who has the capacity of sailing); in the other, it applies to the state (i.e. have a capacity) (un vieux marin is then interpreted as somebody who has had this capacity for a long time).

With this kind of treatment, adjectives which belong to different logical classes are not considered as homonymous. The different senses can be derived from the semantics of the noun and the adjective.