POS Parsing

Syntactic
Parsing

Task of recognizing a sentence
& assigning a syntactic structure

Goal

  • Produce the correct tree

Ambiguity

Occur when grammar can assign
more than one parse to a sentence

Structural Ambiguity

Attachment Ambiguity

  • A particular constituent can be attached
    to the parse tree at more than one place

Coordination Ambiguity

  • Sets of phrases can be conjoined by a conjunction
  • [old [men and women]] vs [[old men] and [women]]

Syntactic
Disambiguation

Statistical Parsing

  • Using probabilistic parsing

Probabilistic
CFG

Augmenting each rule in R with
a conditional probability

∑βP(A→β)=1

Probability
\( = P(A \rightarrow β | A) \)

Dependency
Parsing

Analyzes the grammatical structure of a sentence

Establishing relationships between "head" words & words which modify those heads

Core Relations

Clausal Relations

  • Describe syntactic roles with respect to predicate (often verb)

Modifier Relations

  • Categorize the ways that words that can modify their heads