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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 Sequence.java source file found in the
//original java implementation of OpenNLP.  That source file contains the following header:

//Copyright (C) 2003 Gann Bierner and Thomas 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.

using System;
using System.Collections;

namespace OpenNLP.Tools.Util
{
	/// <summary>Represents a weighted sequence of outcomes. </summary>
	public class Sequence : System.IComparable
	{
		private double mScore;
		private ArrayList mOutcomes;
		private ArrayList mProbabilities;

		/// <summary>
		/// Returns a list of outcomes for this sequence.
		/// </summary>
		/// <returns> a list of outcomes.
		/// </returns>
		public virtual ArrayList Outcomes
		{
			get
			{
				return mOutcomes;
			}
			
		}

		private ArrayList Probabilities
		{
			get
			{
				return mProbabilities;
			}
		}

		/// <summary>
		/// Creates a new sequence of outcomes.
		/// </summary>
		public Sequence()
		{
			mOutcomes = new ArrayList(1);
			mProbabilities = new ArrayList(1);
			mScore = 0;
		}
		
		/// <summary>
		/// Creates a new sequence of outcomes by cloning an existing sequence.
		/// </summary>
		/// <param name="sequenceToCopy">
		/// The sequence to create the clone from.
		/// </param>
		public Sequence(Sequence sequenceToCopy)
		{
			mOutcomes = new ArrayList(sequenceToCopy.Outcomes.Count + 1);
			mOutcomes.AddRange(sequenceToCopy.Outcomes);
			
			mProbabilities = new ArrayList(sequenceToCopy.Probabilities.Count + 1);
			mProbabilities.AddRange(sequenceToCopy.Probabilities);

			mScore = sequenceToCopy.Score;
		}
		
		/// <summary>
		/// Creates a new sequence of outcomes based on an existing sequence.
		/// </summary>
		/// <param name="sequenceToCopy">
		/// The sequence to base the new sequence on.
		/// </param>
		/// <param name="outcome">
		/// An additional outcome to add onto the sequence.
		/// </param>
		/// <param name="probability">
		/// An existing probability to add onto the sequence.
		/// </param>
		public Sequence(Sequence sequenceToCopy, string outcome, double probability)
		{
			mOutcomes = new ArrayList(sequenceToCopy.Outcomes.Count + 1);
			mOutcomes.AddRange(sequenceToCopy.Outcomes);
			mOutcomes.Add(outcome);

			mProbabilities = new ArrayList(sequenceToCopy.Probabilities.Count + 1);
			mProbabilities.AddRange(sequenceToCopy.Probabilities);
			mProbabilities.Add(probability);

			mScore = sequenceToCopy.Score + System.Math.Log(probability);
		}
		
		/// <summary>
		/// Creates a new sequence of outcomes based on a list of outcomes.
		/// Each is given a probability of 1.
		/// </summary>
		/// <param name="outcomes">
		/// List of outcomes to create the sequence from.
		/// </param>
		public Sequence(ArrayList outcomes)
		{
			mOutcomes = outcomes;
			mProbabilities = ArrayList.Repeat(1, mOutcomes.Count);
		}
		
		/// <summary>
		/// Compares two Sequence objects.
		/// </summary>
		/// <param name="o">
		/// Object to compare this Sequence to.
		/// </param>
		/// <returns>
		/// Value indicating which sequence is the larger.
		/// </returns>
		public virtual int CompareTo(object o)
		{
			Sequence sequence = (Sequence) o;

			if (mScore < sequence.Score)
			{
				return 1;
			}
			if (mScore > sequence.Score)
			{
				return -1;
			}
			return 0;
		}
		
		/// <summary>
		/// Tests for equality of Sequence objects.
		/// </summary>
		/// <param name="o">
		/// Object to compare this Sequence to.
		/// </param>
		/// <returns>
		/// True if the objects are equal; false otherwise.
		/// </returns>
		public override bool Equals (object o)
		{
			if (!(o is Sequence))
			{
				return false;
			}
			Sequence sequence = (Sequence) o;
			return mScore == sequence.Score;
		}  

		public override int GetHashCode ()
		{
			return mScore.GetHashCode();
		}  

		public static bool operator == (Sequence firstSequence, Sequence secondSequence)
		{
			return firstSequence.Score == secondSequence.Score;
		}  

		public static bool operator != (Sequence firstSequence, Sequence secondSequence)
		{
			return firstSequence.Score != secondSequence.Score;
		}  

		public static bool operator < (Sequence firstSequence, Sequence secondSequence)
		{
			return firstSequence.Score < secondSequence.Score;
		}  

		public static bool operator > (Sequence firstSequence, Sequence secondSequence)
		{
			return firstSequence.Score > secondSequence.Score;
		}  

		/// <summary>
		/// Adds an outcome and probability to this sequence.
		/// </summary>
		/// <param name="outcome">
		/// the outcome to be added.
		/// </param>
		/// <param name="probability">
		/// the probability associated with this outcome.
		/// </param>
		public virtual void Add(string outcome, double probability)
		{
			mOutcomes.Add(outcome);
			mProbabilities.Add(probability);
			mScore += System.Math.Log(probability);
		}
		
		/// <summary>
		/// Returns an array of probabilities associated with the outcomes of this sequence.
		/// </summary>
		/// <returns>
		/// an array of probabilities.
		/// </returns>
		public virtual double[] GetProbabilities()
		{
			double[] probabilities = new double[mProbabilities.Count];
			GetProbabilities(probabilities);
			return probabilities;
		}
		
		/// <summary>
		/// Populates an array with the probabilities associated with the outcomes of this sequence.</summary>
		/// <param name="probabilities">
		/// a pre-allocated array to use to hold the values of the probabilities of the outcomes for this sequence.
		/// </param>
		public virtual void GetProbabilities(double[] probabilities)
		{
			for (int currentProbability = 0, probabilityCount = mProbabilities.Count; currentProbability < probabilityCount; currentProbability++)
			{
				probabilities[currentProbability] = ((double) mProbabilities[currentProbability]);
			}
		}
		
		/// <summary>
		/// Returns the score of this sequence.
		/// </summary>
		/// <returns>
		/// The score of this sequence.
		/// </returns>
		public double Score
		{
			get
			{
				return mScore;
			}
		}

		public override string ToString()
		{
			return mScore + " " + mOutcomes.ToString();
		}
	}
}

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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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