Improving entity extraction from text using the lookup table feature in rasa_nlu
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README.md

Phrase Matcher Demo

This is a simple demo of the new lookup table feature in rasa_nlu. See the blog post accompanying this repository here

The goal is to show how lookup tables may improve entity extraction under certain conditions and also give some advice on using this feature effectively.

This repo contains two demos:

  1. A simple restaurant example with very few training examples and only one entity.
  2. A medium-sized company name extraction example with a few thousand examples and several entities.

Running the demo.

No installation is necessary although you must have rasa_nlu installed and version > 0.13.3 or above.

To run one or both of the demos:

python run_lookup.py <demo_key>

where <demo_key> is one of {food, company}. If <demo_key> is ommitted, it will run both of the demos.

Code Structure

data/ holds the training data and lookup tables for each of the demos.

models/ is where the models are persisted.

configs/ holds the rasa_nlu configs to do the baseline evaluation and the lookup table evaluation.

img/ stores plots and outputs from the runs.

Cleaning lookup tables

The script filter_lookup.py may be used to clean up lookup tables by removing any elements that match with a cross-list.

You can call this scripy by running

python filter_lookup.py <lookup_in> <cross_list> <lookup_out>

<lookup_in> is a lookup table with newline-separated elements.

<cross_list> is either a comma or newline-separated list of elements that you'd like to remove from <lookup_in>

<lookup_out> is the name of the file that you'd like to write the filtered list to.

Speed Testing

We include the directory speed_test/ for testing the speed of training as a function of the lookup table size.

This generates random lookup tables and times each component of the training and evaluation process. We use the company dataset data/company/company_train_lookup.py.

cd speed_test
python time_lookups.py

See speed_test/README.md for more details.

Ngrams

A simple ngrams tester is included and can be run by

python run_ngrams.py

This loads two lookup tables, data/company/pos_ngrams.txt & data/company/neg_ngrams.txt, each containing ngrams that were found to be influential to classifying phrases as company names. We then compute the f1 score as a function of random noise injected into the entities. The 'noise' value is the probability of a character flip in each character of each company entity in the test set.

This gives the following plot