Class: Treat::Workers::Extractors::NameTag::Stanford

Inherits:
Object
  • Object
show all
Defined in:
lib/treat/workers/extractors/name_tag/stanford.rb

Overview

Named entity tag extraction using the Stanford NLP Deterministic Coreference Resolver, which implements a multi-pass sieve coreference resolution (or anaphora resolution) system based on conditional random fields.

Original paper: Heeyoung Lee, Yves Peirsman, Angel Chang, Nathanael Chambers, Mihai Surdeanu, Dan Jurafsky. Stanford’s Multi-Pass Sieve Coreference Resolution System at the CoNLL-2011 Shared Task. In Proceedings of the CoNLL-2011 Shared Task, 2011.

Constant Summary collapse

@@classifiers = 
{}

Class Method Summary collapse

Class Method Details

.name_tag(entity, options = {}) ⇒ Object 



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# File 'lib/treat/workers/extractors/name_tag/stanford.rb', line 17

def self.name_tag(entity, options = {})

  language = entity.language
  Treat::Loaders::Stanford.load(language)
  
  isolated_token = entity.is_a?(Treat::Entities::Token)
  tokens = isolated_token ? [entity] : entity.tokens
  
  unless classifier = @@classifiers[language]
    model = Treat::Loaders::Stanford.find_model(:ner, language)
    unless StanfordCoreNLP.const_defined?('CRFClassifier')
      StanfordCoreNLP.load_class('CRFClassifier', 'edu.stanford.nlp.ie.crf')
    end
    classifier = StanfordCoreNLP::CRFClassifier.getClassifier(model)
    @@classifiers[language] = classifier
  end
  
  token_list = StanfordCoreNLP.get_list(tokens)
  sentence = classifier.classify_sentence(token_list)
  i = 0
  
  sentence.each do |s_token|
    tag = s_token.get(:answer).to_s.downcase
    tag = nil if tag == 'o'
    return tag if isolated_token
    if tag
      tokens[i].set :name_tag, tag
    end
    i += 1
  end
  
end