Lexicon (An Interacting Subsystem in UG) Part-I

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Lexicon(An Interacting Subsystem in UG)Part-I

• Rajat Kumar Mohanty
• Email rkm_at_cse.iitb.ac.in
• IIT Bombay

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Levels of Representation in Universal Grammar
(UG)

• Lexicon

D-Structure
Move -alpha
S-Structure
LF (logical form)
PF (phonetic form)
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The Theory of UG

• Two conditions
• Compatible with the diversity of existing
  grammars
• Sufficiently constrained and restricted
• Central Concept
• grammar not language.
• Language derivative at a higher level of
  abstraction from actual neural mechanism.

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Interacting subsystems

• UG consists of interacting subsystems
• Various subcomponents of the rule system of
  grammar
• Subsystems of Principles

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Subcomponents

• Subcomponents of the rule system
• Lexicon
• Syntax
• Categorial component
• Transformational component
• PF-component
• LF-component

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Principles

• Subsystem of Principles
• X-bar Theory
• Bounding Theory
• Government Theory
• Theta-theory
• Binding Theory
• Case Theory
• Control Theory

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Lexicon

• Overgeneration
• Subcategorization Restriction
• Selectional Restriction
• Separating the Lexicon from Syntax
• Lexical Derivation

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Overgeneration

• Ungrammaticality
• The boy relied on the girl.
• The boy relied the girl.
• The boy relied.
• Grammatically Sound but Semantically Odd
• The boy frightens sincerity.
• Sincerity kicked the boy.

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Overgeneration

• PS Rules for the given sentences
• S ? NP VP
• VP? V (NP) (PP)
• NP? Det N
• V ? rely
• Det ? the
• N? boy, girl

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Subcategorization Restrictions

• Subcategorization Frames
• Subcategorization Rules

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Subcategorization Frames

• Specify the categorial class of the lexical item
• Specify the environment
• Examples
• kick V _ NP
• cry V _
• rely V _PP
• put V _ NP PP
• think V _ S

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Subcategorization Frames

• The information in the subcategorization frame
  implies that kick can only be inserted under a V
  node in a VP structure in which V has an NP
  sister.
• The subcategorization information is associated
  with the individual lexical items in their
  lexical entries.

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Subcategorization Rules

• These rules make a specific lexical item
  sensitive to the subcategorization properties of
  the lexical item.
• Selection of a frame depends on the
  subcategorization properties of the verb.

Subcategorization Rule


_NP _ _PP _NP PP _S
V
y
/
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Subcategorization Rules

• The boy relied on the girl
• 1. S ? NP VP
• 2. VP ? V (NP) (PP) (S)
• 3. NP ? Det N
• 4. V ? rely / _PP
• 5. P ? on / _NP
• 6. Det ? the
• 7. N ? boy, girl

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Context Free and Context Sensitive Rules

• Rule (4) ensures the non-generation of
• The boy relied.
• The boy relied the girl.
• Rule (4) and (5) are context sensitive rules
• Rule (1-3) are context free rules

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Selectional Restrictions

• Necessity of a Mechanism
• Can we exclude these two ill-formed structures ?
• The boy frightened sincerity.
• Sincerity kicked the boy.
• A system should include a mechanism which ensures
  that only nouns with appropriate properties are
  associated with given verbs in a given context

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Selectional Restrictions

• Inherent Properties of Nouns
• /- ABSTRACT, /- ANIMATE
• Like subcategorization properties, they are
  specified in the lexical entries
• Sincerity ABSTRACT
• Boy ANIMATE
• Lexical information of this type can be used to
  set up a context sensitive rewrite rule

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Selectional Restrictions

• Selectional Rules
• A selectional rule specifies certain selectional
  restrictions associated with a verb (presumably
  other categories N, A, P)

__


/-ABSTARCT
V
y
/
/-ANIMATE
__


__
V
/-ABSTARCT
frighten
/
__
ANIMATE
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Exercises

• Workout the subcategorization frame of each of
  the lexical items aspire, declare, conduct,
  aware, transport, arrange, deliver, silent
• Write selectional rules for the following verbs
  cry, rely, put, think, abandon, aspire

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Exercises

• Consider the following examples
• John believes that Mary left early.
• John believes if Mary left early.
• John wonders that Mary left early.
• John wonders if Mary left early.
• Suggest a formal way of encoding the property of
  the verbs believe and wonder .
• Tips
• Workout the subcategorization frame
• Write the subcategorization rules
• Assign selectional restrictions

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Sources and further reading

• Comsky, Noam. 1965. Aspects of the Theory of
  Syntax. CUP, Cambridge.
• Comsky, Noam. 1981. Lectures on Government and
  Binding. Foris, Dordrecht.
• Ouhalla, Jamal. 1994. Introducing
  Transformational grammar. Arnold, London.

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