The PS grammar is an alternative way of expressing the information in a tree diagram employing rewrite rules. This is a method of structural description. It specifies the subunits and the level at which these units form natural groups. Rewrite rules can generate strings of linguistic elements and provide a constituent analysis of the string.
Suppose the sentence is The boy admires sincerity; the sentence is represented as S. Then we search for the phrase structure rules and rewrite one symbol into another until we reach the ultimate constituents. A rewrite rule is a replacement rule in which the symbol to the left of the arrow is replaced by the expanded form written to the right of the arrow.
S -> NP + VP
Here, S is the symbol that is used to initiate the rewriting. So it is called the initial symbol. The labels, such as NP and VP, are nodes that can be further expanded or rewritten.
NP -> Det + N
VP -> V + NP
Noun Phrase
An NP can be rewritten or expanded in the following way, using symbols:
I) NP -> Pre-det + Det. + Ord.+ Quant. + Adj. phr. + Class. + N.
E.g., All these four very nice Usha fans.
II) NP -> NP + Prepositional phrase
E.g., the soldiers of the enemy camp
III) NP -> NP + Relative Clause
A clause that has an adjective function and modifies an NP is called a relative clause.
E.g., the doctor who visited the old man
IV) NP -> Complement Clause
A complement clause functions as an NP, while a relative clause modifies an NP.
E.g., That he is rich is well known.
V) NPs with compound nouns
E.g., the film star
Verb Phrase
Verb phrases can consist of just the main verb.
E.g., She writes several letters every day.
Verb phrases can also contain one or more auxiliary verbs before the main verb- Auxiliary verbs such as be, have, might etc, are helping verbs and help the main verb to make up verb phrases.
E.g., She is writing.
She has been writing.
I) VP-> Aux.+ MV
E.g., The girl has been crying.
Verbal is identified as the simple form of the verb (MV). It may or may not be followed by other words.
(a) Aux. may be rewritten as tense.
Aux -> Tense {present|past}
E.g., He plays
(b) Aux -> Tense + Modal
E.g., She may play
(c) Aux -> Tense + Perfective
E.g., She had written
(d) Aux -> Tense + Progressive
E.g., She is practising
(e) Aux. -> Tense + Modal + Perfective
E.g., She might have gone.
(f) Aux -> Tense + Perfective + Progressive
E.g., She has been crying.
(g) Aux. -> Tense + Modal + Perfective + Progressive
E.g., She could have been laughing.
II) VP -> Aux.+ be + b-complement
Transformational grammarians do not include be among verbs. They call it copula, i.e., be occurring as the MV is called the copula. This differs from be + -ing suffix, as in She is singing, where be is an Aux. Whatever word follows the copula be may be called b-complement.
E.g., John is courageous.
The b-complement can be an NP, an Adj. or Adv. of place.
E.g., He is the winner.
She is pretty.
It is on the table.
Verbals
Verbals are words that follow the verb.
(a) Verbal -> V
E.g., Mary walks.
(b) Verbal -> V + NP
E.g., Mary writes poems.
(c) Verbal -> V + NP
E.g., Mary became a teacher.
(d) Verbal -> V + Adj.
E.g., Mary became wise.
These verbs may be examined:
- walks – Vi (verb intransitive)
- writes – Vt (verb-transitive)
- became – Vlk (verb linking)
Thus, three types of verbals can be distinguished: Vi occurs without a following NP, Vt is followed by an NP, i.e., the direct object (DO), and an NP or an adjective follows Vlk. An NP that follows a linking verb is called the predicate nominative.
Middle Verbs
There is a fourth type of verb called middle verb (Vmid).
E.g., The new teacher taught the students.