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Statistical parsing of English sentences

, 13 Dec 2006
Shows how to generate parse trees for English language sentences, using a C# port of OpenNLP, a statistical natural language parsing library.
englishparsing_bin.zip
englishparsing_net2_0_bin.zip
englishparsing_net2_0_src.zip
Lithium
Collections
Delegates
Enums
Interfaces
IO
Lithium.csproj.vspscc
LithiumControl.bmp
Shapes
UI
Visitors
ModelConverter
App.ico
ModelConverter.csproj.vspscc
ParseTree
App.ico
ParseTree.csproj.vspscc
ToolsExample
App.ico
ToolsExample.csproj.vspscc
OpenNLP
OpenNLP.csproj.vspscc
SharpEntropy.dll
Tools
Chunker
NameFind
Parser
PosTagger
SentenceDetect
Tokenize
Util
englishparsing_src.zip
Lithium.csproj.user
LithiumControl.bmp
App.ico
ModelConverter.csproj.user
OpenNLP.csproj.user
SharpEntropy.dll
vssver.scc
vssver.scc
vssver.scc
vssver.scc
vssver.scc
vssver.scc
vssver.scc
App.ico
ParseTree.csproj.user
App.ico
ToolsExample.csproj.user
//Copyright (C) 2005 Richard J. Northedge
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library 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 Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser 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.

//This file is based on the POSEventCollector.java and POSEventStream.java source files found in the
//original java implementation of OpenNLP.  Those source files contain the following headers:

// Copyright (C) 2003 Tom Morton
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library 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 Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser 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.

// Copyright (C) 2002 Jason Baldridge and Gann Bierner
// 
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
// 
// This library 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 Lesser General Public License for more details.
// 
// You should have received a copy of the GNU Lesser 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.

using System;
using System.Collections;

namespace OpenNLP.Tools.PosTagger
{
	/// <summary> 
	/// An event generator for the maxent POS Tagger.
	/// </summary>
	public class PosEventReader : SharpEntropy.ITrainingEventReader
	{
		private System.IO.TextReader mTextReader;
		private IPosContextGenerator mContextGenerator;
		private ArrayList mEventList = new ArrayList();
		private int mCurrentEvent = 0;
		
		public PosEventReader(System.IO.TextReader data) : this(data, new DefaultPosContextGenerator())
		{
		}

		public PosEventReader(System.IO.TextReader data, IPosContextGenerator contextGenerator)
		{
			mContextGenerator = contextGenerator;
			mTextReader = data;
			string nextLine = mTextReader.ReadLine();
			if (nextLine != null)
			{
				AddEvents(nextLine);
			}
		}
		
		public virtual bool HasNext()
		{
			return (mCurrentEvent < mEventList.Count);
		}
		
		public virtual SharpEntropy.TrainingEvent ReadNextEvent()
		{
			SharpEntropy.TrainingEvent trainingEvent = (SharpEntropy.TrainingEvent)mEventList[mCurrentEvent];
			mCurrentEvent++;
			if (mEventList.Count == mCurrentEvent)
			{
				mCurrentEvent = 0;
				mEventList.Clear();
				string nextLine = mTextReader.ReadLine();
				if (nextLine != null)
				{
					AddEvents(nextLine);
				}
			}
			return trainingEvent;
		}

		private void AddEvents(string line)
		{
			Util.Pair linePair = ConvertAnnotatedString(line);
			ArrayList tokens = (ArrayList) linePair.A;
			ArrayList outcomes = (ArrayList) linePair.B;
			ArrayList tags = new ArrayList();
					
			for (int currentToken = 0; currentToken < tokens.Count; currentToken++)
			{
				string[] context = mContextGenerator.GetContext(currentToken, tokens.ToArray(), (string[]) tags.ToArray(typeof(string)), null);
				SharpEntropy.TrainingEvent posTrainingEvent = new SharpEntropy.TrainingEvent((string) outcomes[currentToken], context);
				tags.Add(outcomes[currentToken]);
				mEventList.Add(posTrainingEvent);
			}
		}

		private static Util.Pair Split(string input)
		{
			int splitPosition = input.LastIndexOf("_");
			if (splitPosition == -1)
			{
				System.Console.Out.WriteLine("There is a problem in your training data: " + input + " does not conform to the format WORD_TAG.");
				return new Util.Pair(input, "UNKNOWN");
			}
			return new Util.Pair(input.Substring(0, (splitPosition) - (0)), input.Substring(splitPosition + 1));
		}
		
		public static Util.Pair ConvertAnnotatedString(string input)
		{
			ArrayList tokens = new ArrayList();
			ArrayList outcomes = new ArrayList();
			Util.StringTokenizer tokenizer = new Util.StringTokenizer(input);
			string token = tokenizer.NextToken();
			while (token != null)
			{
				Util.Pair linePair = Split(token);
				tokens.Add(linePair.A);
				outcomes.Add(linePair.B);
				token = tokenizer.NextToken();
			}
			return new Util.Pair(tokens, outcomes);
		}
			
//		[STAThread]
//		public static void Main(string[] args)
//		{
//			string sData = "the_DT stories_NNS about_IN well-heeled_JJ communities_NNS and_CC developers_NNS";
//			EventCollector oEventCollector = new PosEventCollector(new System.IO.StringReader(sData), new DefaultPosContextGenerator());
//			Event[] aoEvents = oEventCollector.GetEvents();
//			for (int iCurrentEvent = 0; iCurrentEvent < aoEvents.length; iCurrentEvent++)
//			{
//				System.Console.Out.WriteLine(aoEvents[iCurrentEvent].GetOutcome());
//			}
//		}
	}
}

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About the Author

Richard Northedge
Web Developer
United Kingdom United Kingdom
Richard Northedge is a senior developer with a UK Microsoft Gold Partner company. He has a postgraduate degree in English Literature, has been programming professionally since 1998 and has been an MCSD since 2000.

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