Page 379 - DENG504_LINGUISTICS

Unit 29: Transformational and Phrase Structure Rules

Thus a PS grammar is an alternative way of expressing the information found in a tree diagram by Notes
means of rewrite rules. In this model the linguist formalizes the grammar by means of generative
rules which explicitly assign the correct constituent structure to sentences. Such systems are called
simple ‘phrase-stricture grammars’. This model of grammar shows not only the terminal elements or
constituents of a linear structure but also specifies the subunits and the level at which these units
form natural groups. So the linguist here is interested (1) in the patterns underlying the sentence and
its constituents; and (2) in the syntactic devices used to link the constituents together, and the ways in
which various parts relate to one another.
Without the, axiom, there are bound to be an unlimited number of rules. This implies that we can
neither formulate nor write down such rules in one life-time, which rules out the possibility of someone
using this grammar to master a language. The fact that we learn a language by the time we are three
or four, refutes such an implication and compels us to believe that the rules of a grammar have got to
be finite and not infinite.
Phrase Structure rules of the generative grammar are an amalgamation of the Subject-Predicate and
Parsing systems of the traditional grammars and the IC analysis of the structural grammar. They are
framed to derive a kernel sentence as in the Syntactic Structures (Chomsky, 1957), or, underlying
(deep) strings as in the Aspects (Chomsky, 1965). These rules define basic grammatical relations that
function in the deep structure, categorize the various constituents of a deep structure, and determine
the ordering (organization) of elements in the deep structure. They also make explicit the domination
of one constituent over the other. In short, they make explicit the universal conditions that define
“human language.”
How do Phrase Structure Grammars Work ?

1. First we write down the initial symbol S.
2. Then we search for the Phrase Structure Rule (also known as Constituent Structure Rule,
Branching Rule) which instructs us what to do with the initial symbol; i.e.,
Rules l : S a + b

S

a b
Questions :

1. Are there any more Rules ? Yes, Rules 1 : S a + s + b. Does it apply ? (That is, do we still have
a S after rewriting the initial symbol ?)
No there is no other S.
2. Are there any other Rules ?
No, none.
3. Then, we have got the Terminal String : a + b
or a b (omitting +)

Thus a b is a grammatical sentence of the language.
Let us now consider the other case where we can apply the second rule of formation, Rule 2 :
S a + S + b,
S
Initial Symbol :.S
Rule 1 : S a + b ... not applied
b
Rule 2. : S a + S + b a S
Now we apply Rule 1 : S a + b

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