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Statistical parsing of English sentences

, 13 Dec 2006 458.4K 17.5K 227
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
Lithium.dll
ModelConverter.exe
OpenNLP Tools.chm
OpenNLP.dll
ParseTree.exe
SharpEntropy.dll
ToolsExample.exe
englishparsing_net2_0_bin.zip
ToolsExample.exe
Lithium.dll
ModelConverter.exe
OpenNLP Tools.chm
OpenNLP.dll
ParseTree.exe
SharpEntropy.dll
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 SDEventStream.java source file found in the
//original java implementation of OpenNLP.  That source file contains the following header:

// 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;

namespace OpenNLP.Tools.SentenceDetect
{
	/// <summary>
	/// An implementation of ITrainingEventReader which assumes that it is receiving
	/// its data as one (valid) sentence per token.  The default DataReader
	/// to use with this class is PlainTextByLineDataReader, but you can
	/// provide other types of ITrainingDataReaders if you wish to receive data from
	/// sources other than plain text files; however, be sure that each
	/// token your ITrainingDataReader returns is a valid sentence.
	/// </summary>
	public class SentenceDetectionEventReader : SharpEntropy.ITrainingEventReader
	{
		private SharpEntropy.ITrainingDataReader<string> mDataReader;
		private string mNext;
		private SentenceDetectionEvent mHead, mTail;
        private SharpEntropy.IContextGenerator<Util.Pair<System.Text.StringBuilder, int>> mContextGenerator;
		private System.Text.StringBuilder mBuffer = new System.Text.StringBuilder();
		private IEndOfSentenceScanner mScanner;
		
		/// <summary>
		/// Creates a new <code>SentenceDetectionEventReader</code> instance.  A
		/// DefaultEndOfSentenceScanner is used to locate sentence endings.
		/// </summary>
		/// <param name="dataReader">a <code>ITrainingDataReader</code> value
		/// </param>
		public SentenceDetectionEventReader(SharpEntropy.ITrainingDataReader<string> dataReader) : this(dataReader, new DefaultEndOfSentenceScanner(), new SentenceDetectionContextGenerator(DefaultEndOfSentenceScanner.GetEndOfSentenceCharacters()))
		{
		}
		
		/// <summary>
		/// Class constructor which uses the EndOfSentenceScanner to locate
		/// sentence endings.
		/// </summary>
		public SentenceDetectionEventReader(SharpEntropy.ITrainingDataReader<string> dataReader, IEndOfSentenceScanner scanner) : this(dataReader, scanner, new SentenceDetectionContextGenerator(DefaultEndOfSentenceScanner.GetEndOfSentenceCharacters()))
		{
		}

        public SentenceDetectionEventReader(SharpEntropy.ITrainingDataReader<string> dataReader, IEndOfSentenceScanner scanner, SharpEntropy.IContextGenerator<Util.Pair<System.Text.StringBuilder, int>> contextGenerator)
		{
			mDataReader = dataReader;
			mScanner = scanner;
			mContextGenerator = contextGenerator;
			if (mDataReader.HasNext())
			{
				string current = mDataReader.NextToken();
				if (mDataReader.HasNext())
				{
					mNext = mDataReader.NextToken();
				}
				AddNewEvents(current);
			}
		}
		
		public virtual SharpEntropy.TrainingEvent ReadNextEvent()
		{
			SentenceDetectionEvent topEvent = mHead;
			mHead = mHead.NextEvent;
			if (null == mHead)
			{
				mTail = null;
			}
			return topEvent;
		}
		
		private void AddNewEvents(string token)
		{
			System.Text.StringBuilder buffer = mBuffer;
			buffer.Append(token.Trim());
			int sentenceEndPosition = buffer.Length - 1;
			//add following word to stringbuilder
			if (mNext != null && token.Length > 0)
			{
				int positionAfterFirstWordInNext = mNext.IndexOf(" ");
				if (positionAfterFirstWordInNext != - 1)
				{
					// should maybe changes this so that it usually adds a space
					// before the next sentence, but sometimes leaves no space.
					buffer.Append(" ");
					buffer.Append(mNext.Substring(0, (positionAfterFirstWordInNext) - (0)));
				}
			}
			
			for (System.Collections.IEnumerator iterator = mScanner.GetPositions(buffer).GetEnumerator(); iterator.MoveNext(); )
			{
				int candidate = (int) iterator.Current;
                Util.Pair<System.Text.StringBuilder, int> pair = new Util.Pair<System.Text.StringBuilder, int>(buffer, candidate);
				string type = (candidate == sentenceEndPosition) ? "T" : "F";
				SentenceDetectionEvent sentenceEvent = new SentenceDetectionEvent(type, mContextGenerator.GetContext(pair));
				
				if (null != mTail)
				{
					mTail.NextEvent = sentenceEvent;
					mTail = sentenceEvent;
				}
				else if (null == mHead)
				{
					mHead = sentenceEvent;
				}
				else if (null == mHead.NextEvent)
				{
					mHead.NextEvent = mTail = sentenceEvent;
				}
			}
			
			buffer.Length = 0;
		}
		
		public virtual bool HasNext()
		{
			if (null != mHead)
			{
				return true;
			}
			
			while (null == mHead && (object) mNext != null)
			{
				string current = mNext;
				if (mDataReader.HasNext())
				{
					mNext = (mDataReader.NextToken());
				}
				else
				{
					mNext = null;
				}
				AddNewEvents(current);
			}
			return (null != mHead);
		}
		
//		[STAThread]
//		public static void  Main(System.String[] args)
//		{
//			EventStream es = new SDEventStream(new PlainTextByLineDataStream(new System.IO.StreamReader(System.Console.In)));
//			while (es.hasNext())
//			{
//				System.Console.Out.WriteLine(es.nextEvent());
//			}
//		}
	}
}

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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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