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XML-RPC version of the Stanford POS tagger

branch: master
README
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                              README                                   
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                          Stanford POS Tagger as XML-RPC service 
                          22 August 2010

	MaxentTaggerXML-RPC Service applicable to Stanford POS Tagger, v. 3.0 - 2010-05-10 (http://nlp.stanford.edu/software/tagger.shtml)
                                                                      
	Copyright (C) 2010-present, MetaOptimize LLC

  Coded by Ali Afshar (it.zvision@yahoo.com)
                                                                       
=====================================================================

Contents:
---------

1. Installation 

2. Getting started

   - Running the server
   - Java Client Example
   - Python Client Example

3. History 

4. Copyright

5. How it is done


----------------------------------------------------------------------

NOTE:
-----

The service is packed and delivered as a patch

It contains four modules:

1) edu/stanford/main/MaxentTaggerServer.java
   This is the server module. 

2) edu/stanford/nlp/tagger/maxent/MaxentTagger.java	
	 This is a copy of the module edu/stanford/nlp/tagger/maxent/MaxentTagger.java from Stanford POS Tagger, v. 3.0 - 2010-05-10 with minor changes.
	 
	 Visibilty for the three following methods have been changed.
	 
	 - protected TokenizerFactory<? extends HasWord> chooseTokenizerFactory()
	 changed to:
	 		public TokenizerFactory<? extends HasWord> chooseTokenizerFactory()
	 		
	 - private static String getTsvWords(ArrayList<TaggedWord> s)	
	 changed to:
	 		public static String getTsvWords(ArrayList<TaggedWord> s)
	 		
	 - private static void printErrWordsPerSec(long milliSec, int numWords)
	 changed to:
			public static void printErrWordsPerSec(long milliSec, int numWords)
			
3) edu/stanford/nlp/tagger/maxent/TaggerConfig.java
	 This is a copy of the module edu/stanford/nlp/tagger/maxent/TaggerConfig.java from Stanford POS Tagger, v. 3.0 - 2010-05-10 extended with serverPort parameter

4) edu/stanford/nlp/ling/CoreAnnotations.java
	 This is a copy of the module edu/stanford/nlp/ling/CoreAnnotations.java from Stanford POS Tagger, v. 3.0 - 2010-05-10 with no changes 
	 (MaxentTagger.java requires this, shouldn't really need it since we do not make any changes, (?) maybe a Generic-related issue in the implementaion of the TypesafeMap and/or CoreMap)  


The Service is developed in Java 1.6, on Eclipse under Win XP. 
It has been also tested on Windows XP and Windows 2000.  


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1. Installation:
----------------

Download the Stanford Postagger XML-RPC Service source. 

	 The src structure is: 
	 
		-src  
			-edu
				-stanford
					-main
						- MaxentTaggerServer.java
					-nlp
						-ling
							- CoreAnnotations.java
						-tagger
							-maxent
								- MaxentTagger.java
								- TaggerConfig.java		
		
	Compile and pack class files to a jar (e.g. tagger_server.jar) and copy into stanford-postagger-full-2010-05-26 home directory (TAGGER_HOME).
	 	
 
				
----------------------------------------------------------------------

2. Getting started:
-------------------

- Get stanford-postagger-full-2010-05-26.
  wget http://nlp.stanford.edu/software/stanford-postagger-full-2010-05-26.tgz
  tar zxvf stanford-postagger-full-2010-05-26.tgz
    
- Copy the tagger_server.jar into the stanford-postagger-full-2010-05-26 home directory (TAGGER_HOME)	 
	e.g. E:\progtams\stanford-postagger-full-2010-05-26\tagger_server.jar

- set TAGGER_RPC=%TAGGER_HOME%\tagger_server.jar;%TAGGER_HOME%\stanford-postagger-2010-05-26.jar
	Note tagger_server.jar comes first.
		
- Download:
    http://ftp.us.xemacs.org/pub/mirrors/maven2/xmlrpc/xmlrpc/1.2-b1/xmlrpc-1.2-b1.jar
	and add it also to your classpath.
    

* Running the server

Type at command prompt:
		
		java -cp %TAGGER_RPC%;%CLASSPATH% edu.stanford.main.MaxentTaggerServer -model <modelFile> [-serverPort <port>] [other parameters]  ; See TaggerConfig.java for a list of relevant parameters
		
		e.g. 
		java -cp %TAGGER_RPC%;%CLASSPATH% edu.stanford.main.MaxentTaggerServer -model models\left3words-distsim-wsj-0-18.tagger -serverPort 8090 
		

* Java Client Example
=====================================================
see TaggerClient.java

How to execute the Java client:
'''''''''''''''''''''''''''''''''''''''''''''''''''

Assume xmlrpc-1.2-b1.jar is included in the classpath.
 
Compile and then run the client by typing at command prompt: 

	java -ea TaggerClient <inputFile> [port]    // Default port 8000 is used
	
		e.g.
		java -ea TaggerClient E:\tmp\stanford-postagger-2010-05-26\sample-input.txt 8090

	
	If xmlrpc-1.2-b1.jar is not included in your classpath:
	
		java -ea -cp ./;E:\programs\tools\xmlrpc-1.2-b1\xmlrpc-1.2-b1.jar;	TaggerClient E:\tmp\stanford-postagger-2010-05-26\sample-input.txt 8090
		


* Python Client Example, 
=====================================================

See client.py

How to run the python client
'''''''''''''''''''''''''''''''''''''''''''''''''''

Invoke at command prompt:
    python client.py <inputFile> [port]

e.g.
		python client.py  E:/Temp/stanford-postagger-full-2010-05-26/sample-input.txt  8090  

----------------------------------------------------------------------

3. Further enhancement:
-----------------------

- test it with the latest XML-RPC library.

-----------------------------------------------------------------------

4. Copyright:
-------------



-----------------------------------------------------------------------

5. How it is done:
------------------

The service to be exposed is specified as follows: Given a (.txt) document and a model, words in provided document needed to be tagged.

After some investigation it turned out that the module edu.stanford.nlp.tagger.maxent.MaxentTagger.java is the starting point for this service. 

Assumptions:
	Training has taken place and a model is generated. 
	

Steps:
- Identify the relevant modules 
	See "NOTE:" above
- Create a module in which the XML-RPC service is to be started, in this case it is called edu/stanford/main/MaxentTaggerServer.java. 
- Identify the relevant methods from MaxentTagger and copy them into the edu/stanford/main/MaxentTaggerServer.java. 
	
	Three methods are identified:
	  public void runTagger(BufferedReader reader, BufferedWriter writer, String tagInside, boolean stdin)
   	private static void writeXMLSentence(Writer w, ArrayList<TaggedWord> s, int sentNum)
   	private static String getXMLWords(ArrayList<TaggedWord> s, int sentNum) 

		
- Initializations and modifications
	First we need to do some initializations including loading the model, specifying the output format, encoding etc. 	
	All these parameters are to be loaded prior to start up the service, this is handled by an instance of TaggerConfig.java
	TaggerConfig has been extended with additional parameter (serverPort) to handle the port to which the XML-RPC Service is listening to.
		
	Where we handle these issues is the main method in module MaxentTaggerServer.java 

	public static void main(String[] args) throws Exception  {			
		...
		TaggerConfig config = new TaggerConfig(args);
		MaxentTaggerServer tagger = new MaxentTaggerServer(config);
		try {
			WebServer server = new WebServer(config.getServerPort());
			//server.setParanoid(true);
			server.acceptClient(localhost);
			server.addHandler("tagger", tagger);
			server.start();
			System.out.println("MaxentTaggerServer started....Awaiting requests.");
		} catch (Exception e) {
			//java.lang.RuntimeException: Address already in use: JVM_Bind
			System.out.println(e.getMessage());
		}		
	}
	
		
 Further down in the constructor of MaxentTaggerServer an instance of MaxentTagger is created with a TaggerConfig object as parameter. 
	
	public MaxentTaggerServer(TaggerConfig c) throws IOException, ClassNotFoundException {		
		config = c;
		taggerInstance = new MaxentTagger(c.getModel(), c);		
	}
	
	
- Now we are ready to execute tagger function. 
	
	In the stand alone Stanford POS Tagger it is done by invoking following method in edu.stanford.nlp.tagger.maxent.MaxentTagger. 

 		public void runTagger(BufferedReader reader, BufferedWriter writer, String tagInside, boolean stdin) throws ...     (see line 1289 in MaxentTagger.java)

	We need to make modifications so that given .txt document the method returns a string. The corresponding method in MaxentTaggerServer would look like:

 		public String runTagger(String input) throws ...
	
	That is, given a string "input" (contents of .txt file) a string including tagged words is returned. 		
	The parameter "input" wrapped to a BufferedReader and other three parameters are eliminated. 
	
	We have three other method calls towards MaxentTagger, these methods have gotten their visibility changed to public as mentioned above. 
	
	There are two important methods which handle xml formatting of the output. 
		private static void writeXMLSentence(Writer w, ArrayList<TaggedWord> s, int sentNum)		
		private static String getXMLWords(ArrayList<TaggedWord> s, int sentNum)
		
	These two methods are merged to one singel method with the following definition:
		private static String writeXMLSentence(ArrayList<TaggedWord> s, int sentNum)
	The parameter Writer "w" is eliminated.
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