Language detection

The Annif REST API and CLI include functionalities to detect the language of text given some candidate languages. Annif projects are typically language specific, so a text of a given language needs to be processed with a project intended for that language. Annif's in-built language detection functionality can help in this.

The language detection feature utilizes the Simplemma library, and the candidate languages must be selected from those supported by Simplemma.

REST API

The /v1/detect-language endpoint accepts POST requests with a JSON object containing the text to be analyzed and a list of candidate languages given in IETF BCP 47 codes, for example:

{
  "languages": ["en", "fi"],
  "text": "A quick brown fox jumped over the lazy dog."
}

Note: The number of candidate languages is limited to 5.

The response is a JSON object that provides probability scores for each candidate language:

{
  "results": [
    {"language": "en", "score": 0.85},
    {"language": "fi", "score": 0.1},
    {"language": null, "score": 0.1} 
  ]
}

The scores range from 0 to 1 and a null value is used for an unknown language.

CLI

To detect the language using the CLI, use the detect-language command. Provide the candidate language codes as a comma-separated argument, and the text to analyze via standard input. For example:

$ echo "this is example text" | annif detect-language fi,sv,en
en	1.0000
sv	0.3333
fi	0.0000
?	0.0000

You can also analyze multiple files by specifying their paths, similarly as in the annif suggest command. For example:

$ annif detect-language fi,sv,en README.md LICENSE.txt 
Detected languages for README.md
en	0.7700
sv	0.2100
?	0.2000
fi	0.1400
Detected languages for LICENSE.txt
en	0.8857
sv	0.3714
fi	0.0857
?	0.0571

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