[JAVA] Train Stanford NER Tagger with your own data

NER is an abbreviation for Named Entity Recognition and is one of the tasks of natural language processing called named entity recognition. Stanford NER Tagger is a tool for solving this task. This time, I will train this myself.

Advance preparation

First, download an example of training data. https://github.com/synalp/NER/blob/master/corpus/CoNLL-2003/eng.train

Then download Stanford NER Tagger. https://nlp.stanford.edu/software/CRF-NER.shtml#Download

Then install jdk.

apt install default-jdk

Preparation of training data

Format the downloaded eng.train.

out = []
with open("eng.train", "r") as f:
    for line in f:
        line = line.split()
        if len(line) > 2:
            out.append(str(line[0])+"\t"+str(line[-1]).replace("I-","").replace("B-","")+"\n")
        else:
            out.append("\n")

with open("train.tsv") as f:
    f.write(''.join(out))

Training

Training preparation

1. Unzip the stanford ner tagger and enter the unzipped directory.
2. Put train.tsv in that directory.

Creating a property file

train.prop

trainFile = train.tsv
serializeTo = ner-model.ser.gz
map = word=0,answer=1

useClassFeature=true
useWord=true
useNGrams=true
noMidNGrams=true
maxNGramLeng=6
usePrev=true
useNext=true
useSequences=true
usePrevSequences=true
maxLeft=1
useTypeSeqs=true
useTypeSeqs2=true
useTypeySequences=true
wordShape=chris2useLC
useDisjunctive=true

Save this as a file named train.prop.

Execution of training

java -cp stanford-ner.jar edu.stanford.nlp.ie.crf.CRFClassifier -prop train.prop

Then, the model will be created as a file named ner-model.ser.gz.

Use model from python

You can use the model from python with nltk's Stanford NER Tagger wrapper.

import nltk
from nltk.tag.stanford import StanfordNERTagger
sent = "Balack Obama kills people by AK47"
model = "./ner-model.ser.gz"
jar = "./stanford-ner.jar"
tagger = StanfordNERTagger(model, jar, encoding='utf-8')
print(tagger.tag(sent.split()))

[output]

[('Balack', 'PER'),
 ('Obama', 'PER'),
 ('kills', 'O'),
 ('people', 'O'),
 ('by', 'O'),
 ('AK47', 'O')]

reference

[0] https://nlp.stanford.edu/software/crf-faq.html#a [1] https://blog.sicara.com/train-ner-model-with-nltk-stanford-tagger-english-french-german-6d90573a9486