Centre for Language and Speech Technology

Colibri Core

“Efficient n-gram & skipgram modelling on text corpora„

Colibri Core is software to quickly and efficiently count and extract patterns from large corpus data, to extract various statistics on the extracted patterns, and to compute relations between the extracted patterns. The employed notion of pattern or construction encompasses the following categories:

N-gram extraction may seem fairly trivial at first, with a few lines in your favourite scripting language, you can move a simple sliding window of size **n** over your corpus and store the results in some kind of hashmap. This trivial approach however makes an unnecessarily high demand on memory resources, this often becomes prohibitive if unleashed on large corpora. Colibri Core tries to minimise these space requirements in several ways:

Skipgram and flexgram extraction are computationally more demanding but have been implemented with similar optimisations. Skipgrams are computed by abstracting over n-grams, and flexgrams in turn are computed either by abstracting over skipgrams, or directly from n-grams on the basis of co-occurrence information (mutual pointwise information).

At the heart of the sofware is the notion of pattern models. The core tool, to be used from the command-line, is colibri-patternmodeller which enables you to build pattern models, generate statistical reports, query for specific patterns and relations, and manipulate models.

A pattern model is simply a collection of extracted patterns (any of the three categories) and their counts from a specific corpus. Pattern models come in two varieties:

The Indexed Pattern Model is much more powerful, and allows more statistics and relations to be inferred.

The generation of pattern models is optionally parametrised by a minimum occurrence threshold, a maximum pattern length, and a lower-boundary on the different types that may instantiate a skipgram (i.e. possible fillings of the gaps).

Colibri Core is available as a collection of standalone command-line tools, as a C++ library, and as a Python library.

Documentation & Resources

Colibri Core was developed by Maarten van Gompel at the Centre of Language Studies, Radboud University Nijmegen, under supervision of Antal van den Bosch. Please cite our publication in the Journal of Open Reseach Software in your papers if you make use of Colibri Core.