Siddharth Patwardhan > WordNet-SenseRelate-TargetWord > intro.pod

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NAME ^

intro.pod - introduction to WordNet::SenseRelate::TargetWord

CONTENTS ^

intro.pod, install.pod, utils.pod, modules.pod, developers.pod, config.pod, FDL.txt

SYNOPSIS ^

You can use pod2html, pod2latex, pod2man, or pod2text to get this documentation in a different format. See the man pages for pod2html, etc. These translators should come with Perl, but you can also download them from http://search.cpan.org.

DESCRIPTION ^

This package consists of a set of Perl modules along with supporting Perl programs that perform the task of Word Sense Disambiguation. The program(s) attempt to disambiguate the sense of a single target word in a given context as described by Banerjee and Pedersen (2002), Patwardhan et al. (2003) and Banerjee and Pedersen (2003). This package separates the disambiguation process into the following steps:

(a) Preprocessing

(b) Context Selection

(c) Postprocessing

(d) Sense Selection Algorithm

The context, which is typically 3 to 4 sentences of text, is passed through each of these stages. Each stage does some processing of the context. The final sense selection stage picks a sense of the target word, using the information from the context. For example, in order to determine which sense of a given word is being used in a particular context, the sense having the highest relatedness with its context word senses is most likely to be the sense being used.

Because of the wide range of possibilites for each of the stages, the package has been made highly configurable. The user is allowed to choose different modules for each of the stages. Additionally, various configuration options can be passed to the substages to control their behavior.

The WordNet::SenseRelate::TargetWord initializes the modules specified by the user for each substage. It then accepts instances of text, consisting of a few sentences, with one of the words marked as the target word to be disambiguated. It passes the text through each of the stages, and gets the chosen sense from the last (Algorithm) stage, and return the chosen sense as the answer for that instance. The substages are applied in the following order:

Preprocessing

WordNet::SenseRelate::TargetWord allows the user to apply multiple preprocessing modules to the input text. All of the preprocessing modules specified by the user are applied to the text in the order specified by the user.

Context Selection

The WordNet::SenseRelate::TargetWord package allows the user to select one Context Selection package, which when applied to the context would pick a subset of the words around the target word for the disambiguation algorithm to use in picking the intended sense of the target word.

Postprocessing

Like the preprocessing modules the user can select multiple postprocessing modules that would be applied to the text after the context selection has been done. Before the postprocessing modules are called the program determines the possible senses of the target word and the selected context words. The postprocessing stages are intended for any processing that involves the senses of the context words. For example, applying some heutistics to "prune" some of the senses of the target word, or the context words.

Sense Selection Algorithm

The goal of the sense selection algorithm is to use the senses of the context words to pick one of the senses of the target word as the answer. The WordNet::SenseRelate::TargetWord module allows the user to specify only one Algorithm module.

INSTALL ^

The package can be installed with the following four commands:

 perl Makefile.PL

 make

 make test

 make install

For a more detailed explanation or for non-standard installations, see install.pod.

MODULES ^

In this section, we list the modules provided in the package.

Preprocessing modules

Currently, only one preprocessing module is provided in the package:

WordNet::SenseRelate::Preprocess::Compounds

This module detects collocations within the text, and joins them with underscores. For example, a piece of text such as "the board of directors" would become "the board_of_directors".

Context Selection modules

One context selection module is provided in the package:

WordNet::SenseRelate::Context::NearestWords

This modules picks the N words nearest the target word as the context words that should be used by the disambiguation algorithm. A stop list can be specified to omit words like "a", "an, "the", etc. The value N can be set during initialization.

Postprocessing modules

As of this vesion, there are no postprocessing modules in the package. However, we intend to add some in future releases.

Sense Selection Algorithm

Four sense selection algorithm modules are provided in the pacakge:

WordNet::SenseRelate::Algorithm::Local

This modules selects that sense of the target word which is most related to the senses of the context words. To do this it uses the "Local" disambiguation algorithm as described by Banerjee and Pedersen (2002). In order to determine the relatedness of senses, the algorithm uses one of the WordNet::Similarity measures of relatedness. Using the configuration options for this module, the user can specify which measure the algorithm should use.

WordNet::SenseRelate::Algorithm::Global

This modules selects that sense of the target word which is most related to the senses of the context words. To do this it uses the "Global" disambiguation algorithm as described by Banerjee and Pedersen (2002). This algorithm is somewhat similar to the "Local" algorithm. It differs from the "Local" algorithm, in that it forms all possible combinations of the senses of the context words, and evaluates the semantic relatedness for each combination separately. The combination with the maximum score is is selected, and the sense of the target word in that combination is returned as the answer.

WordNet::SenseRelate::Algorithm::SenseOne

This module provides a baseline for the disambiguation process by always returning the first sense of the target word as the answer.

WordNet::SenseRelate::Algorithm::Random

This module provides another baseline by randomly selecting one of the senses of the target word as the answer.

Apart from all of the modules mentioned above that form the pieces of the bigger structure, the package also contains the WordNet::SenseRelate::TargetWord module which combines the above pieces.

In order to use these modules in a Perl program for Word Sense Disambiguation, we need only create an instance of the WordNet::SenseRelate::TargetWord module in our program, and provide it with options that indicate which of the above modules (along with configuration options) it should use in the disambiguation process.

Additionally, in order to be able to use this package for disambiguating instances from the Senseval2 or the Senseval3 data sets, the WordNet::SenseRelate::Reader::Senseval2 module has also been provided in the package. The reader module reads in an entire Senseval2 formatted XML file and builds a list of instances from the file. A Perl program can then iterate over these instances and pass them to the WordNet::SenseRelate::TargetWord object.

UTILITIES ^

Some Perl utilities that provide command-line and graphical interfaces to the Perl modules are provided in the '/utils' directory of the package.

disamb.pl

Performs Word Sense Disambiguation on Senseval-2 lexical sample data. It uses the WordNet::SenseRelate::Reader::Senseval2 module to read a Senseval2 lexical sample file, and then disambiguates each of the instances using the WordNet::SenseRelate::TargetWord module.

Usage: disamb.pl [ [--config FILE] [--wnpath WNPATH] [--trace] XMLFILE | --help | --version]

--config=FILENAME Specifies a configuration file (FILENAME) to set up the various configuration options.

--wnpath=WNPATH WNPATH specifies the path of the WordNet data files. Ordinarily, this path is determined from the $WNHOME environment variable. But this option overides this behavior.

--trace Indicates that trace information be printed.

--help Displays this help screen.

--version Displays version information.

Example:

To disambiguate an English lexical sample file using the default options

  disamb.pl eng-lex-samp.xml

To dismabiguate an English lexical sample file, specifying configuration options and trace output

  disamb.pl --config config.txt --trace eng-lex-sample.xml
wps2sk.pl

Creates a word#pos#sense to sensekey mapping of a Senseval-2 answer file (output by disamb.pl). In order to be able to evaluate the output of disamb.pl using software provided by the Senseval organizers, we need to covert the output of disamb.pl to the "SenseKey" format.

Usage: wps2sk.pl [ [--wnpath WNPATH] [FILE...] | --help | --version ]

--wnpath=WNPATH WNPATH specifies the path of the WordNet data files. Ordinarily, this path is determined from the $WNHOME environment variable. But this option overides this behavior.

--quiet Run in quiet mode -- does not print informational messages. But it does print warning or error messages if any.

--help Displays this help screen.

--version Displays version information.

Example:

To convert a captured output from disamb.pl

  wps2sk.pl output.txt

Typically used in a pipe with disamb.pl

  disamb.pl xmlfile.xml | wps2sk.pl --quiet
disamb-gui.pl

Performs Word Sense Disambiguation on Senseval-2 lexical sample data (graphical interface to WordNet::SenseRelate::TargetWord). It uses the WordNet::SenseRelate::Reader::Senseval2 module to read a Senseval2 lexical sample file, and then allows the user to pick the instances that she wishes to disambiguate.

Usage: disamb-gui.pl [ [--config FILE] [--wnpath WNPATH] [XMLFILE] | --help | --version]

--config=FILENAME Specifies a configuration file (FILENAME) to set up the various configuration options.

--wnpath=WNPATH WNPATH specifies the path of the WordNet data files. Ordinarily, this path is determined from the $WNHOME environment variable. But this option overides this behavior.

--help Displays this help screen.

--version Displays version information.

CONFIGURATION FILE ^

A configuration file can be passed to both, disamb.pl as well as to disamb-gui.pl in order to set up the configuration parameters for the modules. The format of this file is specified in this section.

The configuration file must start with a header, which is the string "WordNet::SenseRelate::TargetWord" on the first byte of the first line of the file.

It consists of a number of sections. Each section contains a list of modules for that section, along with the configuration options for the modules.

A section starts with the string

  [SECTION:section_name]

A new section header indicates the end of the previous section. The utilies in this package recognize four types of sections:

  [SECTION:PREPROCESS]

  [SECTION:CONTEXT]

  [SECTION:POSTPROCESS]

  [SECTION:ALGORITHM]

Any other section will be ignored by the program, without warning. Each of the sections is used to specify the list of modules for that section. A module is specified by [START modname] and [END] tags appearing on separate lines.

Configuration parameters for the module appear on separate lines in between the start and end tags as PARAMETER=VALUE pairs.

Example config file:

WordNet::SenseRelate::TargetWord

[SECTION:PREPROCESS]

[START WordNet::SenseRelate::Preprocess::Compounds]

[END]

[SECTION:CONTEXT]

[START WordNet::SenseRelate::Context::NearestWords]

windowsize=5

windowstop=/home/sid/window-stop.txt

[END]

[SECTION:POSTPROCESS]

[SECTION:ALGORITHM]

[START WordNet::SenseRelate::Algorithm::Local]

[END]

The above config file has four sections -- PREPROCESS, CONTEXT, POSTPROCESS and ALGORITHM. The PREPROCESS section contains a single module for compound detection, and has no config parameters. The CONTEXT section lists one module (NearestWords), with parameters windowsize and windowstop. There are no modules listed in the POSTPROCESS section. The ALGORITHM section lists the Local disambiguation algorithm module, also with no config parameters.

EXAMPLE USAGE AS AN APPLICATION PROGRAMMING INTERFACE ^

The WordNet::SenseRelate::TargetWord module handles the managerial task of initializing the processing modules, initializing the data and passing it between modules. The following pieces of code can serve as a guide for using the module to disambiguate a word within its context.

We would start by initializing the module:

    use WordNet::SenseRelate::TargetWord;

    # Create a hash with the config options
    my %wsd_options = (preprocess => [],
                       preprocessconfig => [],
                       context => 'WordNet::SenseRelate::Context::NearestWords',
                       contextconfig => {(windowsize => 5,
                                          contextpos => 'n')},
                       algorithm => 'WordNet::SenseRelate::Algorithm::Local',
                       algorithmconfig => {(measure => 'WordNet::Similarity::res')});

    # Initialize the object
    my ($wsd, $error) = WordNet::SenseRelate::TargetWord->new(\%wsd_options, 0);

In the current implementation, an "instance" is a hash reference with these fields: "text", "words", "head", "target", "wordobjects", "lexelt", "id", "answer" and "targetpos". The values of the hash reference corresponding to "text", "words" and "wordobjects" are array references. The remaining values are scalars. So an instance object can be created like so:

    my $hashRef = {};             # Creates a reference to an empty hash.
    $hashRef->{text} = [];        # Value is an empty array ref.
    $hashRef->{words} = [];       # Value is an empty array ref.
    $hashRef->{wordobjects} = []; # Value is an empty array ref.
    $hashRef->{head} = -1;        # Index into the text array (initialized to -1)
    $hashRef->{target} = -1;      # Index into the words & wordobjects arrays (initialized to -1)
    $hashRef->{lexelt} = "";      # Lexical element (terminology from Senseval2)
    $hashRef->{id} = "";          # Some ID assigned to this instance
    $hashRef->{answer} = "";      # Answer key (only required for evaluation)
    $hashRef->{targetpos} = "";   # Part-of-speech of the target word (if known).

The ones that are important to us are wordobjects and target. The wordobjects array is an array of WordNet::SenseRelate::Word objects. Given a word (say "bank"), a WordNet::SenseRelate::Word object can be created like this:

    use WordNet::SenseRelate::Word;

    my $wordobj = WordNet::SenseRelate::Word->new("bank");

The wordobject array represents your sentence/paragraph containing the word to be disambiguated. The target field is an index into this array, pointing to the word to be disambiguated. So, for a given example sentence, the disambiguation code would be as follows:

    my @sentence = ("The", "boat", "ran", "aground", "on", "the", "river", "bank");
    foreach my $theword (@sentence)
    {
      my $wordobj = WordNet::SenseRelate::Word->new($theword);
      push(@{$hashRef->{wordobjects}}, $wordobj);
      push(@{$hashRef->{words}}, $theword);
    }
    $hashRef->{target} = 7;              # Index of "bank"
    $hashRef->{id} = "Instance1";        # ID can be any string.

The remaining fields are not really used by the system, but they could be initialized (for use later in the system):

    $hashRef->{lexelt} = "bank.n";
    $hashRef->{answer} = "bank#n#1";
    $hashRef->{targetpos} = "n";         # n, v, a or r
    $hashRef->{text} = [("The boat ran aground on the river", "bank")];
    $hashRef->{head} = 1;                # Index to bank

Finally, the disambiguation is done as follows:

    my ($sense, $error) = $wsd->disambiguate($hashRef);
    print "$sense\n";

The scalar $sense contains the selected sense of the target word, and can be processed as required.

SOFTWARE COPYRIGHT AND LICENSE ^

Copyright (C) 2005 Ted Pedersen, Siddharth Patwardhan, and Satanjeev Banerjee

This suite of programs is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

Note: The text of the GNU General Public License is provided in the file 'GPL.txt' that you should have received with this distribution.

ACKNOWLEDGEMENTS ^

This research is partially supported by a National Science Foundation Faculty Early CAREER Development Award (#0092784).

REFERENCES ^

  1. S. Patwardhan and T. Pedersen. Using WordNet-based Context Vectors to Estimate the Semantic Relatedness of Concepts. In Proceedings of the EACL 2006 Workshop on Making Sense of Sense: Bringing Computational Linguistics and Psycholinguistics Together, pages 1-8, Trento, Italy, April 2006.
  2. S. Banerjee and T. Pedersen. Extended gloss overlaps as a measure of semantic relatedness. In Proceedings of the Eighteenth International Conference on Artificial Intelligence (IJCAI-03). Acapulco, Mexico. 2003.
  3. S. Patwardhan, S. Banerjee and T. Pedersen. Using Semantic Relatedness for Word Sense Disambiguation. In Proceedings of the Fourth International Conference on Intelligent Text Processing and Computational Linguistics (CiCLING-03). Mexico City, Mexico. 2003.
  4. S. Patwardhan. Incorporating Dictionary and Corpus Information into a Context Vector Measure of Semantic Relatedness. Masters Thesis, University of Minnesota, Duluth. 2003.
  5. S. Banerjee and T. Pedersen. An Adapted Lesk Algorithm for Word Sense Disambiguation Using WordNet. In Proceedings of the Fourth International Conference on Computational Linguistics and Intelligent Text Processing (CICLING-02). Mexico City, Mexico. 2002.
  6. S. Banerjee. Adapting the Lesk algorithm for Word Sense Disambiguation to WordNet. Masters Thesis, University of Minnesota, Duluth. 2002.
  7. Fellbaum C., editor. WordNet: An electronic lexical database. MIT Press. 1998.

SEE ALSO ^

http://groups.yahoo.com/group/senserelate

http://search.cpan.org/dist/WordNet-SenseRelate-TargetWord

http://senserelate.sourceforge.net

AUTHORS ^

 Ted Pedersen, University of Minnesota Duluth
 tpederse at d.umn.edu

 Siddharth Patwardhan, University of Utah
 sidd at cs.utah.edu

 Satanjeev Banerjee, Carnegie Mellon University
 banerjee+ at cs.cmu.edu

DOCUMENTATION COPYRIGHT AND LICENSE ^

Copyright (C) 2005 Ted Pedersen, Siddharth Patwardhan, and Satanjeev Banerjee

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.

Note: a copy of the GNU Free Documentation License is available on the web at http://www.gnu.org/copyleft/fdl.html and is included in this distribution as FDL.txt.

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