Chinese Word Segmentation

Description

WordSegmenterModel (WSM) is based on maximum entropy probability model to detect word boundaries in Chinese text. Chinese text is written without white space between the words, and a computer-based application cannot know a priori which sequence of ideograms form a word. In many natural language processing tasks such as part-of-speech (POS) and named entity recognition (NER) require word segmentation as a initial step.

References:

  • Xue, Nianwen. “Chinese word segmentation as character tagging.” International Journal of Computational Linguistics & Chinese Language Processing, Volume 8, Number 1, February 2003: Special Issue on Word Formation and Chinese Language Processing. 2003.).

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How to use

Use as part of an nlp pipeline as a substitute of the Tokenizer stage.

document_assembler = DocumentAssembler()\
        .setInputCol("text")\
        .setOutputCol("document")

word_segmenter = WordSegmenterModel.pretrained('wordseg_msra', 'zh')\
        .setInputCols("document")\
        .setOutputCol("token")
        
pipeline = Pipeline(stages=[
        document_assembler,
        word_segmenter
        ])

model = pipeline.fit(spark.createDataFrame([[""]]).toDF("text"))

example = spark.createDataFrame(pd.DataFrame({'text': ["""然而,这样的处理也衍生了一些问题。"""]}))

result = model.transform(example)

...

val word_segmenter = WordSegmenterModel.pretrained("wordseg_msra", "zh")
        .setInputCols("document")
        .setOutputCol("token")

val pipeline = new Pipeline().setStages(Array(document_assembler, word_segmenter))

val result = pipeline.fit(Seq.empty["然而这样的处理也衍生了一些问题。"].toDS.toDF("text")).transform(data)

Results

+----------------------------------+--------------------------------------------------------+
|text                              |result                                                  |
+----------------------------------+--------------------------------------------------------+
|然而,这样的处理也衍生了一些问题。|[然而, ,, 这样, 的, 处理, 也, 衍生, 了, 一些, 问题, 。]|
+----------------------------------+--------------------------------------------------------+

Model Information

Model Name: wordseg_msra
Compatibility: Spark NLP 2.7.0+
Edition: Official
Input Labels: [document]
Output Labels: [token]
Language: zh

Data Source

We trained this model on the Microsoft Research Asia (MSRA) data set available on the Second International Chinese Word Segmentation Bakeoff SIGHAN 2005

Benchmarking

| Model         | precision    | recall       | f1-score     |
|---------------|--------------|--------------|--------------|
| WORSEG_CTB    |      0,6453  |      0,6341  |      0,6397  |
| WORDSEG_WEIBO |      0,5454  |      0,5655  |      0,5553  |
| WORDSEG_MSRA   |      0,5984  |      0,6088  |      0,6035  |
| WORDSEG_PKU   |      0,6094  |      0,6321  |      0,6206  |
| WORDSEG_LARGE |      0,6326  |      0,6269  |      0,6297  |