Complements and Adjuncts

Complements and adjuncts have very different structures in the XTAG grammar. Complements are included in the elementary tree anchored by the verb that selects them, while adjuncts do not originate in the same elementary tree as the verb anchoring the sentence, but are instead added to a structure by adjunction. The contrasts between complements and adjuncts have been extensively discussed in the linguistics literature and the classification of a given element as one or the other remains a matter of debate (see [#!rizzi90!#], [#!larson88!#], [#!jackendoff90!#], [#!larson90!#], [#!cinque90!#], [#!obernauer84!#], [#!lasnik-saito84!#], and [#!chomsky86!#]). The guiding rule used in developing the XTAG grammar is whether or not the sentence is ungrammatical without the questioned structure.^4.1 Consider the following sentences:

(2)0(2

(3)

Srini bought a book.  (3)0(3

(4)

Srini bought a book at the bookstore.  (4)0(4

(5)

Srini arranged for a ride.  (5)0(5

(6)

$\ast$Srini arranged. 

Prepositional phrases frequently occur as adjuncts, and when they are used as adjuncts they have a tree structure such as that shown in Figure 4.2(a). This adjunction tree would adjoin into the tree shown in Figure 4.1(a) to generate sentence ((4)). There are verbs, however, such as arrange, hunger and differentiate, that take prepositional phrases as complements. Sentences ((5)) and ((6)) clearly show that the prepositional phrase are not optional for arrange. For these sentences, the prepositional phrase will be an initial tree (as shown in Figure 4.2(b)) that substitutes into an elementary tree, such as the one anchored by the verb arrange in Figure 4.2(c).

   

Figure 4.2: Trees illustrating the difference between Complements and Adjuncts

(a)		(b)		(c)

Virtually all parts of speech, except for main verbs, function as both complements and adjuncts in the grammar. More information is available in this report on various parts of speech as complements: adjectives (e.g. section 6.13), nouns (e.g. section 6.2), and prepositions (e.g. section 6.10); and as adjuncts: adjectives (section 19.1), adverbs (section 19.5), nouns (section 19.2), and prepositions (section 19.4).