dependency_parsing.md

Dependency parsing

Dependency parsing is the task of extracting a dependency parse of a sentence that represents its grammatical structure and defines the relationships between "head" words and words, which modify those heads.

Example:

     root
      |
      | +-------dobj---------+
      | |                    |
nsubj | |   +------det-----+ | +-----nmod------+
+--+  | |   |              | | |               |
|  |  | |   |      +-nmod-+| | |      +-case-+ |
+  |  + |   +      +      || + |      +      | |
I  prefer  the  morning   flight  through  Denver

Relations among the words are illustrated above the sentence with directed, labeled arcs from heads to dependents (+ indicates the dependent).

Penn Treebank

Models are evaluated on the Stanford Dependency conversion (v3.3.0) of the Penn Treebank with predicted POS-tags. Punctuation symbols are excluded from the evaluation. Evaluation metrics are unlabeled attachment score (UAS) and labeled attachment score (LAS). Here, we also mention the predicted POS tagging accuracy.

Model	POS	UAS	LAS	Paper / Source	Code
Deep Biaffine (Dozat and Manning, 2017)	97.3	95.44	93.76	Deep Biaffine Attention for Neural Dependency Parsing	Official
jPTDP (Nguyen and Verspoor, 2018)	97.97	94.51	92.87	An improved neural network model for joint POS tagging and dependency parsing	Official
Andor et al. (2016)	97.44	94.61	92.79	Globally Normalized Transition-Based Neural Networks
Distilled neural FOG (Kuncoro et al., 2016)	97.3	94.26	92.06	Distilling an Ensemble of Greedy Dependency Parsers into One MST Parser
Weiss et al. (2015)	97.44	93.99	92.05	Structured Training for Neural Network Transition-Based Parsing
BIST transition-based parser (Kiperwasser and Goldberg, 2016)	97.3	93.9	91.9	Simple and Accurate Dependency Parsing Using Bidirectional LSTM Feature Representations	Official
Arc-hybrid (Ballesteros et al., 2016)	97.3	93.56	91.42	Training with Exploration Improves a Greedy Stack-LSTM Parser
BIST graph-based parser (Kiperwasser and Goldberg, 2016)	97.3	93.1	91.0	Simple and Accurate Dependency Parsing Using Bidirectional LSTM Feature Representations	Official

The following results are just for references:

Model	UAS	LAS	Paper / Source	Note
Stack-only RNNG (Kuncoro et al., 2017)	95.8	94.6	What Do Recurrent Neural Network Grammars Learn About Syntax?	Constituent parser
Semi-supervised LSTM-LM (Choe and Charniak, 2016) (Constituent parser)	95.9	94.1	Parsing as Language Modeling	Constituent parser
Deep Biaffine (Dozat and Manning, 2017)	95.66	94.03	Deep Biaffine Attention for Neural Dependency Parsing	Stanford conversion v3.5.0

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