Thutmose Tagger: Single-pass Tagger-based ITN Model#
Inverse text normalization(ITN) converts text from spoken domain (e.g., an ASR output) into its written form:
on may third we paid one hundred and twenty three dollars
on may 3 we paid $123
ThutmoseTaggerModel is a single-pass tagger-based model mapping spoken-domain words to written-domain fragments. Additionally this model predicts “semiotic” classes of the spoken words (e.g., words belonging to the spans that are about times, dates, or monetary amounts)
The typical workflow is to first prepare the dataset, which requires to find granular alignments between spoken-domain words and written-domain fragments. An example bash-script for data preparation pipeline is provided: prepare_dataset_en.sh. After getting the dataset you can train the model. An example training script is provided: normalization_as_tagging_train.py. The script for inference from a raw text file is provided here: normalization_as_tagging_infer.py. An example bash-script that runs inference and evaluation is provided here: run_infer.sh.
Quick Start Guide#
To run the pretrained models see Model Inference.
The initial data from which the dataset is prepared is Google text normalization dataset.
It is stored in TAB separated files (
.tsv) with three columns.
The first column is the “semiotic class” (e.g., numbers, times, dates) , the second is the token
in written form, and the third is the spoken form. An example sentence in the dataset is shown below.
In the example,
<self> denotes that the spoken form is the same as the written form.
PLAIN The <self> PLAIN company <self> PLAIN revenues <self> PLAIN grew <self> PLAIN four <self> PLAIN fold <self> PLAIN between <self> DATE 2005 two thousand five PLAIN and <self> DATE 2008 two thousand eight PUNCT . <self> <eos> <eos>
More information about the Google Text Normalization Dataset can be found in the paper RNN Approaches to Text Normalization: A Challenge [NLP-TEXTNORM2].
Our preprocessing is rather complicated, because we need to find granular alignments for semiotic spans that are aligned at phrase-level in Google Text Normalization Dataset. Right now we only provide data preparation scripts for English and Russian languages, see prepare_dataset_en.sh and prepare_dataset_ru.sh. Data preparation includes running the GIZA++ automatic alignment tool, see install_requirements.sh for installation details. The purpose of the preprocessing scripts is to build the training dataset for the tagging model. The final dataset has a simple 3-column tsv format: 1) input sentence, 2) tags for input words, 3) coordinates of “semiotic” spans if any
this plan was first enacted in nineteen eighty four and continued to be followed for nineteen years <SELF> <SELF> <SELF> <SELF> <SELF> <SELF> _19 8 4_ <SELF> <SELF> <SELF> <SELF> <SELF> <SELF> _19_ <SELF> DATE 6 9;CARDINAL 15 16
An example training script is provided: normalization_as_tagging_train.py. The config file used by default is thutmose_tagger_itn_config.yaml. You can change any of the parameters directly from the config file or update them with the command-line arguments.
Most arguments in the example config file are quite self-explanatory (e.g., model.optim.lr refers to the learning rate for training the decoder). We have set most of the hyper-parameters to be the values that we found to be effective (for the English and the Russian subsets of the Google TN dataset). Some arguments that you may want to modify are:
lang: The language of the dataset.
data.train_ds.data_path: The path to the training file.
data.validation_ds.data_path: The path to the validation file.
model.language_model.pretrained_model_name: The huggingface transformer model used to initialize the model weights
model.label_map: The path/…/label_map.txt. This is the dictionary of possible output tags that model may produce.
model.semiotic_classes: The path/to/…/semiotic_classes.txt. This is the list of possible semiotic classes.
Example of a training command:
python examples/nlp/text_normalization_as_tagging/normalization_as_tagging_train.py \ lang=en \ data.validation_ds.data_path=<PATH_TO_DATASET_DIR>/valid.tsv \ data.train_ds.data_path=<PATH_TO_DATASET_DIR>/train.tsv \ model.language_model.pretrained_model_name=bert-base-uncased \ model.label_map=<PATH_TO_DATASET_DIR>/label_map.txt \ model.semiotic_classes=<PATH_TO_DATASET_DIR>/semiotic_classes.txt \ trainer.max_epochs=5
Run the inference:
python examples/nlp/text_normalization_as_tagging/normalization_as_tagging_infer.py \ pretrained_model=itn_en_thutmose_bert \ inference.from_file=./test_sent.txt \ inference.out_file=./output.tsv
The output tsv file consists of 5 columns:
Final output text - it is generated from predicted tags after some simple post-processing.
Sequence of predicted tags - one tag for each input word.
Sequence of tags after post-processing (some swaps may be applied).
Sequence of predicted semiotic classes - one class for each input word.
The model first uses a Transformer encoder (e.g., bert-base-uncased) to build a contextualized representation for each input token. It then uses a classification head to predict the tag for each token. Another classification head is used to predict a “semiotic” class label for each token.
Overall, our design is partly inspired by the LaserTagger approach proposed in the paper Encode, tag, realize: High-precision text editing [NLP-TEXTNORM1].
The LaserTagger method is not directly applicable to ITN because it can only regard the whole non-common fragment as a single replacement tag, whereas spoken-to-written conversion, e.g. a date, needs to be aligned on a more granular level. Otherwise, the tag vocabulary should include all possible numbers, dates etc. which is impossible. For example, given an example pair “over four hundred thousand fish” - “over 400,000 fish”, LaserTagger will need a single replacement “400,000” in the tag vocabulary. To overcome this problem, we use another method of collecting the vocabulary of replacement tags, based on automatic alignment of spoken-domain words to small fragments of written-domain text along with <SELF> and <DELETE> tags.
Eric Malmi, Sebastian Krause, Sascha Rothe, Daniil Mirylenka, and Aliaksei Severyn. Encode, tag, realize: high-precision text editing. arXiv preprint arXiv:1909.01187, 2019.
Richard Sproat and Navdeep Jaitly. Rnn approaches to text normalization: a challenge. arXiv preprint arXiv:1611.00068, 2016.