A Maximum Entropy Model for Prepositional Phrase Attachment
What it is about
The paper models the noun-or-verb attachment of a prepositional phrase with a maximum-entropy classifier over four head words: the verb, the first noun, the preposition and the second noun. Features are questions on single words, on word classes, and on both; the word classes come from a binary tree of mutual-information clusters. Features are chosen greedily by a ranking of log-likelihood gain, not by exhaustive search. On the Wall Street Journal test events the model scores 81.6% with words and classes (77.7% with words only, 79.1% with classes only); on computer-manual text it scores 84.1%. Humans given the same four head words score 88.2%, and humans who read the whole sentence score 93.2%, so the authors locate the gap in the sentence context.
Ideas
- I1. Cluster features in
en: build mutual-information word classes (deterministic, withBTreeMapordering) from the EWT vocabulary and add class-bit features to theenperceptron inen/src/parse.rsanden/src/ptag.rs; measure EWT test LAS with and without them. - I2. Feature selection as an explanation: use the paper's greedy log-likelihood ranking to choose feature templates for the
entagger and report the chosen templates with their gain, so that every template is justified inen explainterms. - I3. Sentence context for attachment: the paper's gap between head words and whole sentence (88.2 to 93.2) motivates testing
en/src/ctx.rsdocument and sentence features on PP attachments in EWT test.
For Mova
The code is en/src/parse.rs, en/src/ptag.rs and en/src/ctx.rs. The chapters are 22. Phrases: noun, adjective, adverb and prepositional phrases and 23-complementation.md. Measure first: the PP-attachment accuracy of the current en parser on EWT test against the paper's 81.6 and its human 93.2 with the sentence, so that the room is clear before any change.
Cite
@inproceedings{ratnaparkhi1994maximum,
title = {{A Maximum Entropy Model for Prepositional Phrase Attachment}},
author = {Ratnaparkhi, Adwait and Reynar, Jeff and Roukos, Salim},
booktitle = {Human Language Technology: Proceedings of a Workshop held at Plainsboro, New Jersey, March 8-11, 1994},
year = {1994},
doi = {10.3115/1075812.1075868},
url = {https://doi.org/10.3115/1075812.1075868}
}References
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