Phrase-Structure Rules inside Transformational–Generative Grammar

Review of Previous Session and Course Road-Map

  • The previous (6th) lecture dealt with Immediate-Constituent (IC) analysis, originated by Leonard Bloomfield (1930s) and later refined with Zellig Harris.
  • Weaknesses of IC noted:
    • No principled way to mark complements vs. adjuncts; all constituents appear on the same tier.
    • Discontinuities, coordination, ambiguous or naturally occurring sentences often cannot be handled.
    • Requires drawing a separate tree for every single sentence; poor descriptive and computational economy.
  • Current block (Sessions 7–8) covers Generative–Transformational Grammar (TGG):
    • Session 7 = Phrase Structure Rules (PSG).
    • Session 8 = Transformational Rules.
    • Two further sessions will treat X-Bar Theory (1980s) and post-GB developments (up to ≈ 2022).

Immediate-Constituent vs. Phrase Structure Example

Consider the three sentences:

  1. The boy read the novel.
  2. The boy read the novel very loudly.
  3. The boy read the novel very loudly in the class.

IC Analysis:

  • Break successively into constituents: (The boy) (read the novel) → The / boy & read / the / novel etc.
  • „the novel", „very loudly", „in the class" are siblings → no hierarchy, no distinction between complement and adjunct.

PSG Analysis:
S \rightarrow NP\;VP
VP \rightarrow V\ (NP)\ (PP)\ (ADVP)

  • „the novel" = complement (required to satisfy verb READ’s argument structure).
  • „very loudly", „in the class" = adjuncts (optional; appear lower in the tree).
  • The tree makes complement/adjunct status and hierarchical ordering explicit.

Generative–Transformational Grammar (TGG)

  • Introduced by Noam A. Chomsky, 1957 (book Syntactic Structures; elaborated in Aspects of the Theory of Syntax 1965).
  • Central claim: humans possess an innate, rule-governed capacity to generate an infinite set of sentences from a finite set of rules (language is linked to human cognition).
  • Two rule systems inside TGG:
    1. Phrase-Structure Rules (a.k.a. Rewrite or Production rules).
    2. Transformational Rules (move, delete, insert constituents, etc.).

Components of Phrase Structure Grammar (PSG)

  1. Lexicon – list of words with syntactic category, sub-category, selectional properties.
  2. Rewrite/Production Rules – context-free schemata such as NP \rightarrow Det\ N.
  3. Syntactic Categories – S, NP, VP, PP, ADJP, ADVP …
  4. Head – obligatory word that determines phrase label (N is head of NP, V of VP, etc.).
  5. Nodes in a tree:
    • Mother, Daughter, Sister relations (like family tree).
    • Terminal nodes = words/lexemes.
  6. Hierarchy – top node S, successive projections downward.

Order Convention When Writing Rules

  1. Begin with S.
  2. Expand VP.
  3. If present, expand PP.
  4. Expand NP.
  5. Finally, adjunct phrases (ADJP, ADVP, etc.).

Worked Example ▸ "The boy went to the park"

Phrase-Structure Tree outline:
\begin{aligned}
S &\rightarrow NP\;VP\
NP &\rightarrow Det\;N\
VP &\rightarrow V\;PP\
PP &\rightarrow P\;NP\
NP &\rightarrow Det\;N
\end{aligned}
Lexical Rules:
Det \rightarrow \text{the}
N \rightarrow \text{boy}\ \ |\ \ \text{park}
V \rightarrow \text{went}
P \rightarrow \text{to}

Derivation Steps (each step replaces the left-most non-terminal using the numbered rule):

  1. S
  2. NP\;VP
  3. Det\;N\;VP
  4. Det\;N\;V\;PP
  5. Det\;N\;V\;P\;NP
  6. Det\;N\;V\;P\;Det\;N
  7. Replace terminals → the boy went to the park.

Types of PSG Rules

• Categorial Rules – combine abstract categories (context-free):
S \rightarrow NP\;VP
VP \rightarrow V\;NP
• Lexical Rules – map categories onto concrete words:
Det \rightarrow the/ a/ this
V_{past} \rightarrow went/ loved/ ate

Productivity vs. Restriction

  • Pattern Det\ N\ V\ Det\ N can generate infinite sentences:
    The girl sang a song; The man wrote the letter; …
  • Adding lexical rules restricts possibilities, but syntactic acceptability is still larger than semantic acceptability.

Sub-Categorisation & Selectional Restrictions

  • Sub-categories further refine categories (e.g. N{prop}, N{pron}, V{trans}, V{intrans}).
  • Argument Structure: verbs specify number & type of complements.
    • cry 〈NP[agent]〉 (intransitive) → “The baby cried.” complete.
    • kick 〈NP[agent], NP[theme]〉 (transitive) → “The boy kicked.” is incomplete; needs object.
  • Selectional Restrictions ensure semantic fit (animacy, concreteness, thematic roles):
    • Structurally OK but semantically odd: The bone ate the dog.
    • Violates verb’s selectional rule: EAT expects an animate subject, edible object.

Advantages of PSG over IC Analysis

  1. Clear hierarchical representation; complements vs. adjuncts visible.
  2. General, flexible, rule-economical – one rule set generates many sentences.
  3. Formal & systematic – suitable for computational models (NLP, parsers, MT).
  4. Captures syntax–semantics interface via sub-categorisation & selectional rules.
  5. Strong descriptive power – handles complex, coordinated, or discontinuous constructions.
  6. Modular – rules reusable across sentences.
  7. Pedagogical value – clarifies subject/verb/object patterns; aids error diagnosis.
  8. Compatible with later theories: Government-Binding, Minimalism, Dependency, Case & Theta Theory, etc.

Key Terminology & Symbols

  • S – Sentence clause node.
  • NP, VP, PP, ADJP, ADVP – phrasal categories.
  • Det, N, V, P – lexical categories.
  • Head – obligatory element determining phrase label.
  • Complement – obligatory sister to head (licensed by sub-cat frame).
  • Adjunct – optional modifier phrase.
  • Argument – NP (or clause/PP) demanded by predicate’s theta grid.
  • Rewrite arrow \rightarrow – “is expanded as”.
  • Hash # – silent boundary markers before and after sentence.
  • Terminal node – lexeme; non-terminal – category symbol.

Connections & Implications

  • IC analysis provided first structural insight; PSG refines this with explicit hierarchy and rule generativity.
  • PSG lays groundwork for transformational component: once base structure is built, transformations can move/delete constituents to yield surface forms (e.g. Passive, Questions, WH-movement).
  • Sub-categorisation & selectional mechanisms anticipate later developments such as Theta Theory, Case Theory, X-Bar schema, and Minimalist feature checking.
  • Computational linguistics (e.g. context-free parsing, Treebank annotation) still largely rests on PSG notions.

Practical Study Tips

  1. Practise drawing trees and writing the corresponding rule list + derivation.
  2. Always state category rules first, lexical rules second.
  3. Respect the conventional order: S\rightarrow VP\rightarrow PP\rightarrow NP …
  4. Test grammaticality:
    • Syntactic test → matches rule inventory.
    • Semantic test → satisfies selectional restrictions.
  5. Identify complements vs. adjuncts with deletion and obligatoriness tests.
  6. Memorise common sub-categorisation frames (e.g. V[ditrans] 〈NP, NP〉 = give).