Introduction to Natural Language Processing (600.465)HMM Algorithms: Trellis and Viterbi

HMM: The Two Tasks

Trellis - Deterministic Output

Creating the Trellis: The Start

Trellis: The Next Step

Trellis: The Last Step

PPT Slide

General Trellis: The Next Step

Trellis: The Complete Example

The Case of Trigrams

Trigrams with Classes

Class Trigrams: the Trellis

Overlapping Classes

Overlapping Classes: Trellis Example

Trellis: Remarks

The Viterbi Algorithm

The Crucial Observation

Viterbi Example

Viterbi Computation

n-best State Sequences

Tracking Back the n-best paths

Pruning