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Lingua-Identify-0.05
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SYNOPSIS

use Lingua::Identify qw(langof);
$a = langof($textstring); # gives the most probable language

@a = langof($textstring); # gives pairs of languages / probabilities
                          # sorted from most to least probable

%a = langof($textstring); # gives a hash of language / probability

# or the hard (expert) way (see section OPTIONS, under HOW TO PERFORM
# IDENTIFICATION)

$a = langof({ method => [qw/smallwords prefix2 suffix2/] },$textstring);

DESCRIPTION

Lingua::Identify identifies the language a given string or file is written in.

See section WHY LINGUA::IDENTIFY for a list of Lingua::Identify's strong points.

See section KNOWN LANGUAGES for a list of available languages and HOW TO PERFORM IDENTIFICATION to know how to really use this module.

If you're in a hurry, jump to section EXAMPLES, way down below.

Also, don't forget to read the following section, IMPORTANT WARNING.

IMPORTANT WARNING

Take a word that exists in two different languages, take a good look at it and answer this question: "What language does this word belong to?".

You can't give an answer like "Language X", right? You can only say it looks like any of a set of languages.

Similarly, it isn't always easy to identify the language of a text if the only two active languages are very similar.

Now that we've taken out of the way the warning that language identification is not 100% accurate, please keep reading the documentation.

WHY LINGUA::IDENTIFY

You might be wondering why you should use Lingua::Identify instead of any other tool for language identification.

Here's a list of Lingua::Identify's strong points:

  • 4 different methods of language identification and still growing (see METHODS OF LANGUAGE IDENTIFICATION for more details on this one);

  • it's free and its source is open;

  • it's portable (it's Perl, which means it will work in lots of different platforms);

  • it's a module, which means you can easily write your own application (be it CGI, TK, whatever) using it;

  • it comes with langident, which means you don't actually need to write your own application;

  • lots of languages (OK, so I only have 19 so far... but that is intencional!! Just wait a little while);

  • it's flexible (you can actually chose the methods to use and their relevance, and pretty soon you'll be able to chose some other things)

  • it's easy to deal with languages (you can activate and deactivate the ones you chose whenever you want to, which can improve your times and accuracy);

  • and other things too, probably.

HOW TO PERFORM IDENTIFICATION

To identify the language a given text is written in, use the langof function. To get a single value, do:

$language = langof($text);

To get the most probable language and also the percentage of its probability, do:

($language, $probability) = langof($text);

If you want a hash where each active language is mapped into its percentage, use this:

%languages = langof($text);

OPTIONS

langof can also be given some configuration parameters, in this way:

$language = langof(\%config, $text);

These parameters are detailed here:

  • method

    You can chose which method or methods to use, and also the relevance of each of them.

    To chose a single method to use:

    langof( {method => 'smallwords' }, $text);

    To chose several methods:

    langof( {method => [qw/prefixes2 suffixes2/]}, $text);

    To chose several methods and give them different weight:

    langof( {method => {smallwords => 0.5, ngrams3 => 1.5} }, $text);

    To see the list of available methods, see section METHODS OF LANGUAGE IDENTIFICATION.

    If no method is specified, the configuration for this parameter is the following (this might change in the future):

    method => {
  smallwords => 0.5,
  prefixes2  => 1,
  suffixes3  => 1,
  ngrams3    => 1.3
};

LANGUAGE IDENTIFICATION IN GENERAL

Language identification is based in patterns.

In order to identify the language a given text is written in, we repeat a given process for each active language (see section LANGUAGES MANIPULATION); in that process, we look for common patterns of that language. Those patterns can be prefixes, suffixes, common words, ngrams or even sequences of words.

After repeating the process for each language, the total score for each of them is then used to compute the probability (in percentage) for each language to be the one of that text.

METHODS OF LANGUAGE IDENTIFICATION

Lingua::Identify currently comprises four different ways for language identification, in a total of thirteen variations of those.

The available methods are the following: smallwords, prefixes1, prefixes2, prefixes3, prefixes4, suffixes1, suffixes2, suffixes3, suffixes4, ngrams1, ngrams2, ngrams3 and ngrams4.

Here's a more detailed explanation of each of those ways and those methods

Small Word Technique - smallwords

The "Small Word Technique" searches the text for the most common words of each active language. These words are usually articles, pronouns, etc, which happen to be (usually) the shortest words of the language; hence, the method name.

This is usually a good method for big texts, especially if you happen to have few languages active.

Prefix Analysis - prefixes1, prefixes2, prefixes3, prefixes4

This method analyses text for the common prefixes of each active language.

The methods are, respectively, for prefixes of size 1, 2, 3 and 4.

Suffix Analysis - suffixes1, suffixes2, suffixes3, suffixes4

Similar to the Prefix Analysis (see above), but instead analysing common suffixes.

The methods are, respectively, for suffixes of size 1, 2, 3 and 4.

Ngram Categorization - ngrams1, ngrams2, ngrams3, ngrams4

Ngrams are sequences of tokens. You can think of them as syllables, but they are also more than that, as they are not only comprised by characters, but also by spaces (delimiting or separating words).

Ngrams are a very good way for identifying languages, given that the most common ones of each language are not generally very common in others.

This is usually the best method for small amounts of text or too many active languages.

The methods are, respectively, for ngrams of size 1, 2, 3 and 4.

LANGUAGES MANIPULATION

When trying to perform language identification, Lingua::Identify works not with all available languages, but instead with the ones that are active.

By default, all available languages are active, but that can be changed by the user.

For your convenience, several methods regarding language manipulation were created. In order to use them, load the module with the tag :language_manipulation.

These methods work with the two letters code for languages.

activate_language

Activate a language

activate_language('en');

# or

activate_language($_) for get_all_languages();
activate_all_languages

Activates all languages

activate_all_languages();
deactivate_language

Deactivates a language

deactivate_language('en');
deactivate_all_languages

Deactivates all languages

deactivate_all_languages();
get_all_languages

Returns the names of all available languages

my @all_languages = get_all_languages();
get_active_languages

Returns the names of all active languages

my @active_languages = get_active_languages();
get_inactive_languages

Returns the names of all inactive languages

my @active_languages = get_inactive_languages();
is_active

Returns the name of the language if it is active, an empty list otherwise

if (is_active('en')) {
  # YOUR CODE HERE
}
is_valid_language

Returns the name of the language if it exists, an empty list otherwise

if (is_valid_language('en')) {
  # YOUR CODE HERE
}
set_active_languages

Sets the active languages

set_active_languages('en', 'pt');

# or

set_active_languages(get_all_languages());

KNOWN LANGUAGES

Currently, Lingua::Identify knows the following languages:

AF - Afrikaans =item BR - Breton =item BS - Bosnian =item CY - Welsh =item DA - Danish =item DE - German =item EN - English =item EO - Esperanto =item ES - Spanish =item FI - Finnish =item FR - French =item FY - Frisian =item IT - Italian =item LA - Latin =item NL - Dutch =item NO - Norwegian =item PT - Portuguese =item SQ - Albanian =item SV - Swedish

TO DO

  • Implement something like a confidence_level(@results)

  • Add a section with examples, in the documentation;

  • Add examples of the values returned;

  • Configuration parameter to let the user chose which part(s) of the text to use;

  • Configuration parameter to let the user chose a maximum size of text to deal with;

  • WordNgrams based methods;

  • Easy way to learn new languages;

  • More languages;

  • File recognition and treatment;

  • Create sets of languages and permit their activation/deactivation;

SEE ALSO

langident(1), Text::ExtractWords(3), Text::Ngram(3), Text::Affixes(3).

A linguist and/or a shrink.

The latest CVS version of Lingua::Identify can be attained at http://natura.di.uminho.pt/natura/viewcvs.cgi/Lingua/Identify/

AUTHOR

Jose Alves de Castro, <cog@cpan.org>

COPYRIGHT AND LICENSE

Copyright (C) 2004 by Jose Alves de Castro

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.4 or, at your option, any later version of Perl 5 you may have available.