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WordNet::Similarity::lUser)Contributed Perl DocumenWordNet::Similarity::lin(3)

       WordNet::Similarity::lin	- Perl module for computing semantic
       relatedness of word senses using	the information	content	based measure
       described by Lin	(1998).

	 use WordNet::Similarity::lin;

	 use WordNet::QueryData;

	 my $wn	= WordNet::QueryData->new();

	 my $mymeasure = WordNet::Similarity::lin->new($wn);

	 my $value = $mymeasure->getRelatedness("car#n#1", "bus#n#2");

	 ($error, $errorString)	= $mymeasure->getError();

	 die "$errorString\n" if($error);

	 print "car (sense 1) <-> bus (sense 2)	= $value\n";

       Lin (1998) describes a method to	compute	the semantic relatedness of
       word senses using the information content of the	concepts in WordNet
       and the 'Similarity Theorem' (also described in the paper). This	module
       implements this measure of semantic relatedness of concepts.

       $lin->getRelatedness ($synset1, $synset1)
	   Computes the	relatedness of two word	senses using an	information
	   content scheme.  The	relatedness is equal to	twice the information
	   content of the LCS divided by the sum of the	information content of
	   each	input synset.

	   Parameters: two word	senses in "word#pos#sense" format.

	   Returns: Unless a problem occurs, the return	value is the
	   relatedness score.  If no path exists between the two word senses,
	   then	a large	negative number	is returned.  If an error occurs, then
	   the error level is set to non-zero and an error string is created
	   (see	the description	of getError()).	 Note: the error level will
	   also	be set to 1 and	an error string	will be	created	if no path
	   exists between the words.

       The relatedness value returned by the lin measure is a number equal to
       2A *A IC(lcs)A /A (IC(synset1)A +A IC(synset2)).	 Where IC(x) is	the
       information content of x.  One can observe, then, that the relatedness
       value will be greater-than or equal-to zero and less-than or equal-to

       If the information content of any of either synset1 or synset2 is zero,
       then zero is returned as	the relatedness	score, due to lack of data.
       Ideally,	the information	content	of a synset would be zero only if that
       synset were the root node, but when the frequency of a synset is	zero,
       we use the value	of zero	as the information content because of a	lack
       of better alternatives.

       The semantic relatedness	modules	in this	distribution are built as
       classes that expose the following methods:

       See the WordNet::Similarity(3) documentation for	details	of these

       Typical Usage Examples

       To create an object of the lin measure, we would	have the following
       lines of	code in	the Perl program.

	  use WordNet::Similarity::lin;
	  $measure = WordNet::Similarity::lin->new($wn,	'/home/sid/lin.conf');

       The reference of	the initialized	object is stored in the	scalar
       variable	'$measure'. '$wn' contains a WordNet::QueryData	object that
       should have been	created	earlier	in the program.	The second parameter
       to the 'new' method is the path of the configuration file for the lin
       measure.	If the 'new' method is unable to create	the object, '$measure'
       would be	undefined. This, as well as any	other error/warning may	be

	  die "Unable to create	object.\n" if(!defined $measure);
	  ($err, $errString) = $measure->getError();
	  die $errString."\n" if($err);

       To find the semantic relatedness	of the first sense of the noun 'car'
       and the second sense of the noun	'bus' using the	measure, we would
       write the following piece of code:

	  $relatedness = $measure->getRelatedness('car#n#1', 'bus#n#2');

       To get traces for the above computation:

	  print	$measure->getTraceString();

       However,	traces must be enabled using configuration files. By default
       traces are turned off.

       The behavior of the measures of semantic	relatedness can	be controlled
       by using	configuration files. These configuration files specify how
       certain parameters are initialized within the object. A configuration
       file may	be specified as	a parameter during the creation	of an object
       using the new method. The configuration files must follow a fixed

       Every configuration file	starts with the	name of	the module ON THE
       FIRST LINE of the file. For example, a configuration file for the lin
       module will have	on the first line 'WordNet::Similarity::lin'. This is
       followed	by the various parameters, each	on a new line and having the
       form 'name::value'. The 'value' of a parameter is optional (in case of
       boolean parameters). In case 'value' is omitted,	we would have just
       'name::'	on that	line. Comments are supported in	the configuration
       file. Anything following	a '#' is ignored till the end of the line.

       The module parses the configuration file	and recognizes the following

	   The value of	this parameter specifies the level of tracing that
	   should be employed for generating the traces. This value is an
	   integer equal to 0, 1, or 2.	If the value is	omitted, then the
	   default value, 0, is	used. A	value of 0 switches tracing off. A
	   value of 1 or 2 switches tracing on.	 A trace level of 1 means the
	   synsets are represented as word#pos#sense strings, while for	level
	   2, the synsets are represented as word#pos#offset strings.

	   The value of	this parameter specifies whether or not	caching	of the
	   relatedness values should be	performed.  This value is an integer
	   equal to  0 or 1.  If the value is omitted, then the	default	value,
	   1, is used. A value of 0 switches caching 'off', and	a value	of 1
	   switches caching 'on'.

	   The value of	this parameter indicates the size of the cache,	used
	   for storing the computed relatedness	value. The specified value
	   must	be a non-negative integer.  If the value is omitted, then the
	   default value, 5,000, is used. Setting maxCacheSize to zero has the
	   same	effect as setting cache	to zero, but setting cache to zero is
	   likely to be	more efficient.	 Caching and tracing at	the same time
	   can result in excessive memory usage	because	the trace strings are
	   also	cached.	 If you	intend to perform a large number of
	   relatedness queries,	then you might want to turn tracing off.

	   The value of	this parameter indicates whether or not	a unique root
	   node	should be used.	In WordNet, there is no	unique root node for
	   the noun and	verb taxonomies. If this parameter is set to 1 (or if
	   the value is	omitted), then certain measures	(wup, path, lch, res,
	   lin,	and jcn) will "fake" a unique root node. If the	value is set
	   to 0, then no unique	root node will be used.	 If the	value is
	   omitted, then the default value, 1, is used.

	   The value for this parameter	should be a string that	specifies the
	   path	of an information content file containing the frequency	of
	   occurrence of every WordNet concept in a large corpus. A number of
	   utility programs are	included in this distribution that can be used
	   to generate an infocontent file (see	utils.pod).  If	no path	is
	   specified, then the default infocontent file	is used, which was
	   generated from SemCor using the sense-tags.

       perl(1),	WordNet::Similarity(3),	WordNet::QueryData(3)

	 Ted Pedersen, University of Minnesota Duluth
	 tpederse at

	 Siddharth Patwardhan, University of Utah, Salt	Lake City
	 sidd at

	 Jason Michelizzi, University of Minnesota Duluth
	 mich0212 at

       Copyright (c) 2005, Ted Pedersen, Siddharth Patwardhan and Jason

       This program 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
       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: a copy of the GNU General Public License is available on the web
       at <>	and is included	in this
       distribution as GPL.txt.

perl v5.32.0			  2008-03-27	   WordNet::Similarity::lin(3)


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