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Anusha Das Asst: Professor Dept: of English Bishop Moore College Mavelikara
❖ Phrase structure grammar was introduced by Noam Chomsky in the 1950s, building on the tradition of Immediate Constituent Analysis. Syntactic Structures (1957)
➢A more sophisticated model of grammar called Phrase structure grammar evolved out of IC analysis. ➢PS grammars contain a set of rules called Phrase Structure rules or rewrite rules. ➢Rewrite rules provide a set of instruction . ➢A rewrite rule is a replacement rule in which the symbols to the left of the arrow is replaced by the expanded form written to the right of the arrow.
•S NP+VP • Here S (Sentence) is rewritten as NP (Noun Phrase) + VP (Verb Phrase) • The labels such as NP and VP are nodes that can further be expanded or rewritten. • NP Det + N • VP Aux. + V + NP + Prep. Ph • The rewrite rules represent how morphemes are organized into words, words into phrases, and phrases into sentences.
PS grammars have an advantage over the IC model in that the labels are in-built in rewrite rules, and the rules
themselves can be arranged in a sequence so that each rule can be used to rewrite the output of the previous
one.
(1) S NP+VP (2) NP Det + N (3) VP V + NP Applying rule 2 to the output of rule1, we get S Det + N+ VP ; and applying rule 3 to this we get S Det + N+ V + NP ; and applying rule 2 once again S Det + N+ V + Det + N This final string beyond which the symbols do not take us is a terminal string.
• The representation of the structure of a sentence is called its Phrase Marker or P Marker. • The usual form of a P Marker is a tree with labelled nodes. • The P Marker of the sentence, My father gave my son a gift, is:
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Limitations of PS Grammar Fails to show inter-sentence relationships. Discontinuous constituents cannot be accommodated by PS rules. The close relationship between the verb and the particle in phrases like call off, take off, cannot be shown by PS rules. Cannot account for certain types of ambiguities. The property of recursion cannot be accounted. Stylistic variations are also not accountable by PS rules.