Lingua/Identify version 0.06 ============================ Lingua::Identify - Language identification =head1 SYNOPSIS use Lingua::Identify qw(:language_identification); $a = langof($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); =head1 DESCRIPTION C identifies the language a given string or file is written in. See section WHY LINGUA::IDENTIFY for a list of C'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. =head1 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. =head1 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: =over 6 =item * it's free and its source is open; =item * it's portable (it's Perl, which means it will work in lots of different platforms); =item * 4 different methods of language identification and still growing (see METHODS OF LANGUAGE IDENTIFICATION for more details on this one); =item * it's a module, which means you can easily write your own application (be it CGI, TK, whatever) using it; =item * it comes with I, which means you don't actually need to write your own application; =item * 19 languages and growing; =item * 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) =item * 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); =item * and other things too, probably. =back =head1 HOW TO PERFORM IDENTIFICATION To identify the language a given text is written in, use the I 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); =head2 OPTIONS I can also be given some configuration parameters, in this way: $language = langof(\%config, $text); These parameters are detailed here: =over 6 =item * B 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} }, $text); To see the list of available methods, see section METHODS OF LANGUAGE IDENTIFICATION. If no method is specified, the configuration for this parameter is the following (this might change in the future): method => { smallwords => 0.5, prefixes2 => 1, suffixes3 => 1, ngrams3 => 1.3 }; =back =head2 ACCURACY After getting the results into an array, its first element is the most probable language. That doesn't mean it is very probable or not. You can find more about the likeliness of the results to be accurate by computing its confidence level. use Lingua::Identify qw/:language_identification/; my @results = langof($text); my $confidence_level = confidence(@results); # $confidence_level now return a value between 0 and 1; the higher that # value, the more accurate the results seem to be =head3 =head1 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. =head1 METHODS OF LANGUAGE IDENTIFICATION C currently comprises four different ways for language identification, in a total of thirteen variations of those. The available methods are the following: B, B, B, B, B, B, B, B, B, B, B, B and B. Here's a more detailed explanation of each of those ways and those methods =head2 Small Word Technique - B 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. =head2 Prefix Analysis - B, B, B, B 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. =head2 Suffix Analysis - B, B, B, B 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. =head2 Ngram Categorization - B, B, B, B 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. =head1 LANGUAGE MANIPULATION When trying to perform language identification, C 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. =over 6 =item B Activate a language activate_language('en'); # or activate_language($_) for get_all_languages(); =item B Activates all languages activate_all_languages(); =item B Deactivates a language deactivate_language('en'); =item B Deactivates all languages deactivate_all_languages(); =item B Returns the names of all available languages my @all_languages = get_all_languages(); =item B Returns the names of all active languages my @active_languages = get_active_languages(); =item B Returns the names of all inactive languages my @active_languages = get_inactive_languages(); =item B Returns the name of the language if it is active, an empty list otherwise if (is_active('en')) { # YOUR CODE HERE } =item B Returns the name of the language if it exists, an empty list otherwise if (is_valid_language('en')) { # YOUR CODE HERE } =item B Sets the active languages set_active_languages('en', 'pt'); # or set_active_languages(get_all_languages()); =item B Given the two letter tag of a language, returns its name my $language_name = name_of('pt'); =back =head1 KNOWN LANGUAGES Currently, C knows the following languages: =over 6 =item 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 =back =head1 EXAMPLES =head2 THE BASIC EXAMPLE Check the language a given text file is written in: use Lingua::Identify qw/langof/; my $text = join "\n", <>; # identify the language by letting the module decide on the best way # to do so my $language = langof($text); =head2 IDENTIFYING BETWEEN TWO LANGUAGES Check the language a given text file is written in, supposing you happen to know it's either Portuguese or English: use Lingua::Identify qw/langof activate_language/; activate_language(qw/pt en/); my $text = join "\n", <>; # identify the language by letting the module decide on the best way # to do so my $language = langof($text); =head1 TO DO =over 6 =item * Add more examples in the documentation; =item * Add examples of the values returned; =item * Configuration parameter to let the user chose which part(s) of the text to use; =item * Configuration parameter to let the user chose a maximum size of text to deal with; =item * WordNgrams based methods; =item * Easy way to learn new languages; =item * More languages; =item * File recognition and treatment; =item * Create sets of languages and permit their activation/deactivation; =item * What happens when { method => [] } ? =back =head1 SEE ALSO langident(1), Text::ExtractWords(3), Text::Ngram(3), Text::Affixes(3). A linguist and/or a shrink. The latest CVS version of C can be attained at http://natura.di.uminho.pt/natura/viewcvs.cgi/Lingua/Identify/ =head1 AUTHOR Jose Castro, C<< >> =head1 COPYRIGHT & LICENSE Copyright 2004 Jose Castro, All Rights Reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. =cut