Architecture

Annif architecture

Basic concepts

An installation of Annif may contain multiple independent projects, each of which specifies a set of settings (e.g. language and indexing vocabulary). Projects are limited to a single language; multilingual indexing can be performed by defining multiple projects, one per language.

Each project defines a (typically large) number of subjects, which reflect concepts from an indexing vocabulary. Subjects are typically created from a corpus extracted from existing metadata records and/or indexed documents.

Further, there can be several independent backends that provide analysis functionality. Backends can be integrated into Annif itself, or external services queried via APIs. A project can make use of several backends and combine their analysis results.

Software architecture

Annif has a core application (using Flask), which provides both a REST API (when run as a web application) and a command line interface.

In addition, there are separate, independent command line utilities for corpus management, quality evaluation and other auxiliary functions.