Corpus formats

Corpus formats

Annif uses different kinds of corpora. This document specifies the formats.

Full-text document corpus

The full text corpus is a directory with UTF-8 encoded text files that have the file extension .txt.

The directory may also contain subject files that list the assigned subjects for each file. The file name is the same as the document file, but with the file extension .key. For example, document1.txt may have a corresponding subject file document1.key. Subject files come in two formats:

Simple subject file format

This file lists subject labels, UTF-8 encoded, one per line. For example:

networking
computer science
Internet Protocol

Note that the labels must exactly match the preferred labels of concepts in the subject vocabulary.

This format corresponds to the Maui topic file format.

Extended subject file format

This is otherwise similar to the simple subject file format, but the subject file is now a UTF-8 encoded TSV (tab separated values) file with the file extension .tsv, where the first column contains a subject URI and the second column its label. For example:

<http://example.org/thesaurus/subj1>	networking
<http://example.org/thesaurus/subj2>	computer science
<http://example.org/thesaurus/subj3>	Internet Protocol

Any additional columns beyond the first two are ignored.

When using this format, subject comparison is performed based on URIs, not the labels. Since URIs are more persistent than labels, this ensures that subjects can be matched even if the labels have changed in the subject vocabulary.

Subject corpus

TBD

Metadata only corpus

TBD