Syntax: Structural Descriptions of Sentences

Outline

• Constituency
• How does this notion arise?
• Type of constituents
• Representation: Tree Structure
• Formal device: Context Free Grammars
• Derived tree and derivation tree
• Grammar Equivalence
• Strong and weak generative capacity
• Chomsky Normal Form
• Other Formal Frameworks (Tree-Adjoining Grammar)
• Other topics in syntax
• Dependency
• Spoken language syntax
• Structural Priming

Constituency

• Words are grouped into part-of-speech groups
• Similar morphological inflections
• Allows us to create new word forms (“blog”, “xerox”)
• Nouns, Verbs, Determiners, Adjectives etc…
• Certain sequences of words in a sentence are grouped as constituents
• Distributionally similar behavior
• cohesive units (move around in a sentence as a unit)
• In the morning I take a walk
• I take a walk in the morning
• Substrings are typed “Clause”, “Noun Phrase”, “Verb Phrase” “Preposition Phrase” etc.

Constituency – contd.

• Examples of constituents:
• Noun phrase:
• the dog, two big light blue vans
• Preposition phrase:
• in the box, under the bridge
• Clause:
• the dog bit the man, John thought the dog bit the man
• The type of a constituent is derived from the “head word” of the constituent.

Constituent Structure

• Decomposition of a sentence into its constituents.
• Attaching constituents to each other to reflect relations among words: Emergence of Tree Structure
• John saw the man with the telescope
• (S (NP John) saw (NP (NP the man) (PP with (NP the telescope))))
• (S (NP John) saw (NP the man) (PP with (NP the telescope))))
• Select a sentence from a newspaper text and provide its constituent structure.
• Evidence of another constituent – verb phrase (“VP”)
• Substring involving a verb move around and can be referred to as a unit.
• VP-fronting (and quickly clean the carpet he did! )
• VP-ellipsis (He cleaned the carpets quickly, and so did she )
• Can have adjuncts before and after VP, but not in VP (He often eats beans, *he eats often beans )