Rene Descartes
Consider the following sentences :
- The fathe wept silently.
- The father silently wept.
Both mean the same thing despite the position of the adverb. The phrase structure rules place the adverb at the end of the VP, thereby accounting for (1). How can (2) be accounted for ? If we suggest a phrase structure rule with two optional adverbs, like this :
VP --- (Adv) V (NP) (PP) (Adv)
we are faced with the unacceptable possibility of generating ungrammatical strings such as :
The father cleverly wept bitterly.
A solution to this problem is to allow the phrase structure rules to generate the adverb in VP final position, and have another formal device, called a transformational rule, move the adverb in front of the verb, thus deriving the structure that represents (2) from the structure that represents (1).
The basic sentences of the language, whose phrase structure trees are called deep structures, are specified by the phrase structure rules. Variants on those basic sentence structures are derived via transformations.
The structures of sentences that we actually spak--to which the rules of phonology are applied--are called surface structures. If no transformation apply then surface structure is the end result after all transformations have had their effect.
Above, the (1) tree is the deep structure, underlying both sentences (1) and (2). The surface structure of (1) is the same as its deep structure because no transformation has been applied to it. The surface structure of (2), however, is the (2) tree because the adverb-moving transformation alters its deep structure.
According to the same transformational theories, certain obligatory transformations apply to all deep structures. Thus deep and surface are never identical. In this introductory treatment we are unable to provide such details.
Much syntactic knowledge not revealed by phrase structure rules in accounted for by transformations, which alter phrase structure trees by moving, adding, or deleting elements. In particular, families of structurally related sentences are revealed by virtue of havinf the same deep structure, with surface structure differences created by transformational rules.
A transformation similar to the one that moves adverbs moves prepositional phrases when they occur immediately under the VP. It would be responsible foe In the house, the puppy found the ball, and so on.
Further proof of the structure dependency of transformations is the fact that With a telescope, the boy saw the man is not ambiguous. It has only the meaning 'the boy used a telescope to see the man', the meaning corresponding to the phrase structure in which the PP is immediately under the VP. The structure corresponding to the other meaning 'the boy saw the man who had a telescope' has its PP in the NP. The transformation does not apply to it because the structural requirements are not met.
Another transformation deletes that when it precedes a sentence in direct object position, but not in subject position, as illustrated by these pairs :
I know that you know.
I know you know.
That you know bothers me
You know bothers me
This is a further demonstration that transformations are structure dependent. Trasformations also reveal speaker knowledge about the systematic relationship between statements and questions. Consider again the following :
The boy is sleeping.
The boy can sleep.
The boy will sleep.
Word such as is, can, and will are in a class of auxiliary verbs (Aux), which includes be and have as well as may, might, would, could and several others. They are sometones referred to as helping verbs auxiliary modals. They occur in such structures as this one :
We haven't given the S-rule for this structure. It would be S--- NP Aux VP.
Now consider the interrogative sentences corresponding to the declarative ones just given :
Is the boy sleeping ?
Can the boy sleep ?
Will the boy sleep ?
The interrogratives are related to their declarative counterparts in a simple way. In the questions the Aux occurs at the beginning of the sentence rather than after the subject NP.
This relationship can be accounted for by a trasformation that moves the Aux to the front of the sentence. Phrase structure rules need only generate declarative sentence as deep structures. S transformation derives the surface structure of the corresponding interrogatives.
Consider now the following declaratife/intrrogative sets of sentences :
The boy who is sleeping was dreaming.
Was the boy who is sleeping dreaming ?
Is the boy who sleep was dreaming ?
The who can sleep will dream.
Will the boy who can sleep dream ?
Can the boy who will sleep dream ?
The ungrammatical sentences show that in forming question it is the auxiliary of the tpomost S, that is, the one following the entire first NP, that appears at the front of the sentence, not simply the first auxiliary in the sentence. This is illustrated in the following simplified phrase structure trees.
This is further evidence that syntactic categories such as noun phrase are basic structures in language. It is also further evidence of the structure-dependent nature of transformational rules. Transformations such as the one for forming questions must refer to structure, and not only true in English. Simillar constrains and similar rules occur in other languages, as shown by the folowing sentences in Spanish :
El hombre esta en la casa.
The man is in the house.
Esta el hombre en la casa ?
Is the man in the house ?
El hombre esta contento.
The man is happy.
Esta el hombre contento ?
Is the man happy ?
El hombre, que este contento, esta en la casa.
The man, who is happy, in the house.
Esta el hombre, que esta contento, en la casa ?
Is the man, who is happy, in the house ?
Esta el hombre, que contento, esta en la casa ?
Is the man, who happy, is in the house ?
More than one transformation may act on a deep structure. When they do, they do so one after the other. Cosider is the father silently weeping ? Its deep structure is the father is weeping silently. The adverb-moving transformation produces the underlying structure the father is silently weeping. The question transformation acts on this structure to produce the surface structure is the father silently weeping ? This is illustrated in the following diagram :
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