PolyglotDB is a Python package that focuses on representing linguistic data in relational and graph databases.

PolyglotDB represents language (speech and text corpora) using the annotation graph formalism put forth in Bird and Liberman (2001). Annotations are represented in a directed acyclic graph, where nodes are points in time in an audio file or points in a text file. Directed edges are labelled with annotations, and mulitples levels of annotations can be included or excluded as desired. They put forth a relational formalism for annotation graphs, and later work implemented the formalism in SQL.

Recently, NoSQL databases have been rising in popularity, and one type of these is the graph database. In this type of database, nodes and relationships are primitives rather than relational tables. Graph databases map on annotation graphs in a much cleaner fashion than relational databases. The graph database used is Neo4j (http://neo4j.com/).

Relational databases are also used in PolyglotDB. Lexicons and segmental inventories are represented in a relational database. These types of linguistic representations map well onto relational databases.

The idea of using multiple languages or technologies that suit individual problems has been known, particularly in the realm of merging SQL and NoSQL databases, as "polyglot persistence."

PolyglotDB was originally created for use in Phonological CorpusTools (http://phonologicalcorpustools.github.io/CorpusTools/), developed at the University of British Columbia. However, primary development shifted to the umbrella of Montreal Corpus Tools, developed by members of the Montreal Language Modelling Lab at McGill University.

Further documentation, including installation, can be found at http://polyglotdb.readthedocs.org/en/latest/.

Bird, S., & Liberman, M. (2001). A formal framework for linguistic annotation. Speech communication, 33(1), 23-60.