langidentification: Language identification using fastText for Romanized South Asian and Arabic Scripts

This package is a language detector built using fastText with the objective of identifying languages written in non-native romanized scripts. There are two models supported in this package: original and augmented.

The original model was trained on freely available data found on the Tatoeba website. It is trained for 105 languages for which at least 100 sample sentences were present in the data.

The augmented model was trained on all the data used for the original model with the addition of three more datasets:

• The Dakshina Dataset (romanized sentences), with Wikipedia sentence data representing 12 South Asian languages: Bengali (bn), Gujarati (gu), Kannada (kn), Malayalam (ml), Sinhala (si), Tamil (ta), Telugu (te), Hindi (hi), Marathi (mr), Punjabi (pa), Urdu (ur) and Sindhi (sd)
• The Tunisian Arabizi Dialectal Dataset, representing Tunisian Arabic, which displays frequent use of French loanwords
• The Arabizi Identification in Twitter Data dataset, representing Egyptian and Lebanese Arabic, which have some use of English and French loanwords

Although built using fastText, these models are not comparable to the official fastText models, which are built on more data than the Tatoeba dataset. These models are however capable of identifying romanized South Asian language and Arabic (ar) text with the suffix -rom.

Model Performance

Model	Precision	Recall	F1 score
original	0.79	0.65	0.65
augmented	0.75	0.66	0.66

Installation

pip install langidentification

Usage

Valid model_types are original and augmented. The augmented model is capable of making romanized language predictions.

Both models are hosted on GitHub releases and are downloaded at runtime if not found.

>>> from langidentification import LangIdentification
>>> model = LangIdentification(model_type='augmented')
INFO:root:Model langdetect_augmented.ftz was not found. Checking for models directory and creating if not available...

INFO:root:Downloading langdetect_augmented.ftz...

100% [......................................................................] 276567331 / 276567331INFO:root:Loading model langdetect_augmented.ftz...

>>> model.predict_lang('ithu velai seyyuma?')
(('__label__ta-rom',), array([0.87046105]))

What is fastText and how were these models built?

fastText is the implementation of a text embedding method presented in Enriching Word Vectors with Subword Information by Bojanowski et al.

This method is an enhancement of the Word2vec skipgram model which attempts to learn a vector representation for every word by training it to predict other words that appear in the context of the given word. The objective of the skipgram model is to find a set of parameters, i.e. word vectors, such that the likelihood of observing a certain context word given a certain target word is maximized.

fastText builds on the skipgram model by representing words as a sum of the vector representations of their constituent character n-grams and training with the goal of independently predicting the presence of context words. "Positive" examples, being the actual context words, and "negative" examples, being other words randomly drawn from the vocabulary, are used to train on.

For example, in the sentence She is a pretty cat., if the target word is pretty, over the course of training, the vector representation for pretty should evolve to be closer to the representations for the words a and cat and further from other randomly sampled words, such as computer or dirt. As the word vector for pretty is adjusted during this process, so are the constituent character n-gram vectors, e.g. for pre, etty and rett.

The intuition here is that training subword representations helps to more accurately capture nuances in word morphology.

The character n-grams used for the models in this package are between two and four characters long. The vector representations learned are in 50 dimensions.

The models were quantized to make them smaller and faster at inference time.

What is quantization?

Quantization (relevant SciPy modules) is a process by which the embedding vectors (n vectors x d dimensions) are split into m distinct subvectors (n vectors x d/m dimensions), and then a k-means clustering algorithm is run on each of those subvectors. In doing so, a set of centroids (k clusters x d/m dimensions) is identified for each subvector.

This set of centroids acts as the encoding with which to transform the original word vectors (n vectors x d dimensions) into quantized vectors (n vectors x m dimensions). For each one of m subvectors, each of the original word vectors is classified with the cluster number or centroid index of the centroid closest to it. In this way, each word gets assigned m values, producing a final matrix of n vectors x m dimensions.