POS Tagging (Parts of Speech Tagging ) is the process of assigning correct Parts of Speech Tag to words in a text. You can find a more elaborated definition from the wiki article “Part-of-speech tagging”.

So many POS Taggers are available for English under GPL and other licences. Some of the famous taggers are ‘Stanford POS Tagger’, Brill POS Tagger’, ‘Genia Tagger’ etc… Have a look on the Stanford NLP repository link.

Here in this post I would like to show how POS Tagging can be done with a simple Perl script.

There is Pertl module available in the CPAN site called Lingua::EN::Tagger . It is a tagger module for English and some other Europian Languages. Let us see how it can be used for POS Tagging.

Installing Lingua::EN::Tagger in GNU/Linux

Open Terminal. Run cpan as root. Type install Lingua::EN::Tagger enter(Assumes that you are connected to Internet). Follow the instructions. Make sure that tagger is installed. Exit CPAN.

Using Lingua::EN::Tagger

Now open your favourite editor (I prefer VIM). Copy and paste/type the below given code and save it in to a file called ‘tager.pl’. Run ‘perl tager.pl your_text_file .

#!/usr/bin/env perl
use Lingua::EN::Tagger qw(add_tags);
my $postagger = new Lingua::EN::Tagger;

while (<>) {
    chomp $_;
    my $text = $_;

    my $tagged = $postagger->add_tags($text);

    print $tagged, "\n";
}

Code Explanation

use Lingua::EN::Tagger qw(add_tags);

Imports Lingua::EN::Tagger

my $postagger = new Lingua::EN::Tagger;

Creates object of the tgger. Then it reads a text file given as argument and performs the tagging. Happy Hacking!!!!!

Migrated from my old blog jaganadhg.freeflux.net