Phrase Structure Grammar

PS Grammar

1. PHRASE STRUCTURE GRAMMAR Anusha Das Asst: Professor Dept: of English Bishop Moore College Mavelikara

2. Phrase structure grammar was introduced by Noam Chomsky in the 1950s, building on the tradition of Immediate Constituent Analysis. Syntactic Structures (1957)

3. Basic Concepts Every word belongs to a lexical category. Lexical categories form heads of phrases. A phrase is built up around a single word (head), which extends it’s properties to the entire phrase. Phrases are generated by rules of the grammar (phrase structure rules). In a tree, each subtree needs to correspond by a phrase structure rule in the grammar .

4. Phrase Structure Rules illustrate mathematically our knowledge of how the basic units of a sentence are assembled. The theory of rules states that there is a limited number of rules that are carefully ordered: There is a limited number of rules which serve to reflect the linguistic competence and knowledge of a native speaker. These rules are arranged in order : rule 1 must precede rule 2, which must precede rule 3, etc. These rules can be illustrated in phrase structure trees. These rules can be equated mathematically in phrase structure rules.

5. The predecessor to phrase structure rules was an approach to syntax used by structural linguists called “ immediate constituent analysis ,” which accounted for the linear order of words on the surface and the hierarchical structure of the sentence. It was based on the principle that words enter into relationship with one another within coherent units known as constituents, the proper subparts of sentences. An even older form of phrase structure grammar is the sentence diagramming of traditional grammar. What came before Phrase Structure Rules?

6. Argument against Immediate Constituent Analysis Noam Chomsky argued that immediate constituent analysis, though not wrong, was insufficient since it dealt only with surface order. It could not account for the relation between an active and corresponding passive sentence or a declarative and corresponding interrogative sentence.

7. 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.

8. 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.

9. 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.

10. 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 .

11. 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:

12. 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.