2. Phrase structure grammar was introduced by
Noam Chomsky in the 1950s, building on the
tradition of Immediate Constituent Analysis.
Syntactic Structures (1957)
3.
4.
5.
6.
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. (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.
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.
13. 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.
