//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 BuildContextGenerator.java source file found in the
//original java implementation of OpenNLP. That source file contains the following header:
//Copyright (C) 2003 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.Generic;
using System.Text;
namespace OpenNLP.Tools.Parser
{
/// <summary>
/// Class to generator predictive contexts for deciding how constituents should be combined together.
/// </summary>
public class BuildContextGenerator : SharpEntropy.IContextGenerator
{
private const string mEndOfSentence = "eos";
/// <summary>
/// Creates a new context generator for making decisions about combining constituents together.
/// </summary>
public BuildContextGenerator()
{
}
/// <summary>
/// Returns the predictive context used to determine how the constituent at the specified index
/// should be combined with other constituents.
/// </summary>
/// <param name="input">
/// Object array containing an array of Parse objects (the uncombined constituents), and the index of the
/// relevant constituent.
/// </param>
public virtual string[] GetContext(object input)
{
object[] parameters = (object[]) input;
return GetContext((Parse[]) parameters[0], ((int) parameters[1]));
}
private string MakeConstituent(Parse inputParse, int index)
{
StringBuilder feature = new StringBuilder(20);
feature.Append(index).Append("=");
if (inputParse != null)
{
if (index < 0)
{
feature.Append(inputParse.Label).Append("|");
}
feature.Append(inputParse.Type).Append("|").Append(inputParse.Head.ToString());
}
else
{
feature.Append(mEndOfSentence).Append("|").Append(mEndOfSentence).Append("|").Append(mEndOfSentence);
}
return feature.ToString();
}
private string MakeConstituentBackOff(Parse inputParse, int index)
{
StringBuilder feature = new StringBuilder(20);
feature.Append(index).Append("*=");
if (inputParse != null)
{
if (index < 0)
{
feature.Append(inputParse.Label).Append("|");
}
feature.Append(inputParse.Type);
}
else
{
feature.Append(mEndOfSentence).Append("|").Append(mEndOfSentence);
}
return feature.ToString();
}
/// <summary>
/// Returns the predictive context used to determine how the constituent at the specified index
/// should be combined with other constituents.
/// </summary>
/// <param name="constituents">
/// The constituents which have yet to be combined into new constituents.
/// </param>
/// <param name="index">
/// The index of the constituent whcihi is being considered.
/// </param>
/// <returns>
/// the context for building constituents at the specified index.
/// </returns>
public virtual string[] GetContext(Parse[] constituents, int index)
{
List<string> features = new List<string>(100);
int constituentCount = constituents.Length;
//default
features.Add("default");
// cons(-2), cons(-1), cons(0), cons(1), cons(2)
// cons(-2)
Parse previousPreviousParse = null;
Parse previousParse = null;
Parse currentParse = null;
Parse nextParse = null;
Parse nextNextParse = null;
if (index - 2 >= 0)
{
previousPreviousParse = constituents[index - 2];
}
if (index - 1 >= 0)
{
previousParse = constituents[index - 1];
}
currentParse = constituents[index];
if (index + 1 < constituentCount)
{
nextParse = constituents[index + 1];
}
if (index + 2 < constituentCount)
{
nextNextParse = constituents[index + 2];
}
// cons(-2), cons(-1), cons(0), cons(1), cons(2)
string previousPreviousConstituent = MakeConstituent(previousPreviousParse, - 2);
string previousConstituent = MakeConstituent(previousParse, - 1);
string currentConstituent = MakeConstituent(currentParse, 0);
string nextConstituent = MakeConstituent(nextParse, 1);
string nextNextConstituent = MakeConstituent(nextNextParse, 2);
string previousPreviousConstituentBackOff = MakeConstituentBackOff(previousPreviousParse, - 2);
string previousConstituentBackOff = MakeConstituentBackOff(previousParse, - 1);
string currentConstituentBackOff = MakeConstituentBackOff(currentParse, 0);
string nextConstituentBackOff = MakeConstituentBackOff(nextParse, 1);
string nextNextConstituentBackOff = MakeConstituentBackOff(nextNextParse, 2);
// cons(-2), cons(-1), cons(0), cons(1), cons(2)
features.Add(previousPreviousConstituent);
features.Add(previousPreviousConstituentBackOff);
features.Add(previousConstituent);
features.Add(previousConstituentBackOff);
features.Add(currentConstituent);
features.Add(currentConstituentBackOff);
features.Add(nextConstituent);
features.Add(nextConstituentBackOff);
features.Add(nextNextConstituent);
features.Add(nextNextConstituentBackOff);
// cons(-1,0), cons(0,1)
features.Add(previousConstituent + "," + currentConstituent);
features.Add(previousConstituentBackOff + "," + currentConstituent);
features.Add(previousConstituent + "," + currentConstituentBackOff);
features.Add(previousConstituentBackOff + "," + currentConstituentBackOff);
features.Add(currentConstituent + "," + nextConstituent);
features.Add(currentConstituentBackOff + "," + nextConstituent);
features.Add(currentConstituent + "," + nextConstituentBackOff);
features.Add(currentConstituentBackOff + "," + nextConstituentBackOff);
// cons3(-2,-1,0), cons3(-1,0,1), cons3(0,1,2)
features.Add(previousPreviousConstituent + "," + previousConstituent + "," + currentConstituent);
features.Add(previousPreviousConstituentBackOff + "," + previousConstituent + "," + currentConstituent);
features.Add(previousPreviousConstituent + "," + previousConstituentBackOff + "," + currentConstituent);
features.Add(previousPreviousConstituentBackOff + "," + previousConstituentBackOff + "," + currentConstituent);
features.Add(previousPreviousConstituentBackOff + "," + previousConstituentBackOff + "," + currentConstituentBackOff);
features.Add(previousConstituent + "," + currentConstituent + "," + nextConstituent);
features.Add(previousConstituentBackOff + "," + currentConstituent + "," + nextConstituent);
features.Add(previousConstituent + "," + currentConstituent + "," + nextConstituentBackOff);
features.Add(previousConstituentBackOff + "," + currentConstituent + "," + nextConstituentBackOff);
features.Add(previousConstituentBackOff + "," + currentConstituentBackOff + "," + nextConstituentBackOff);
features.Add(currentConstituent + "," + nextConstituent + "," + nextNextConstituent);
features.Add(currentConstituent + "," + nextConstituentBackOff + "," + nextNextConstituent);
features.Add(currentConstituent + "," + nextConstituent + "," + nextNextConstituentBackOff);
features.Add(currentConstituent + "," + nextConstituentBackOff + "," + nextNextConstituentBackOff);
features.Add(currentConstituentBackOff + "," + nextConstituentBackOff + "," + nextNextConstituentBackOff);
// punct
string currentParseWord = currentParse.ToString();
if (currentParseWord == "-RRB-")
{
for (int parseIndex = index - 1; parseIndex >= 0; parseIndex--)
{
Parse testParse = constituents[parseIndex];
if (testParse.ToString() == "-LRB-")
{
features.Add("bracketsmatch");
break;
}
if (testParse.Label.StartsWith(MaximumEntropyParser.StartPrefix))
{
break;
}
}
}
if (currentParseWord == "-RCB-")
{
for (int parseIndex = index - 1; parseIndex >= 0; parseIndex--)
{
Parse testParse = constituents[parseIndex];
if (testParse.ToString() == "-LCB-")
{
features.Add("bracketsmatch");
break;
}
if (testParse.Label.StartsWith(MaximumEntropyParser.StartPrefix))
{
break;
}
}
}
if (currentParseWord == "''")
{
for (int parseIndex = index - 1; parseIndex >= 0; parseIndex--)
{
Parse testParse = constituents[parseIndex];
if (testParse.ToString() == "``")
{
features.Add("quotesmatch");
break;
}
if (testParse.Label.StartsWith(MaximumEntropyParser.StartPrefix))
{
break;
}
}
}
if (currentParseWord == "'")
{
for (int parseIndex = index - 1; parseIndex >= 0; parseIndex--)
{
Parse testParse = constituents[parseIndex];
if (testParse.ToString() == "`")
{
features.Add("quotesmatch");
break;
}
if (testParse.Label.StartsWith(MaximumEntropyParser.StartPrefix))
{
break;
}
}
}
if (currentParseWord == ",")
{
for (int parseIndex = index - 1; parseIndex >= 0; parseIndex--)
{
Parse testParse = constituents[parseIndex];
if (testParse.ToString() == ",")
{
features.Add("iscomma");
break;
}
if (testParse.Label.StartsWith(MaximumEntropyParser.StartPrefix))
{
break;
}
}
}
if (currentParseWord == (".") && index == constituentCount - 1)
{
for (int parseIndex = index - 1; parseIndex >= 0; parseIndex--)
{
Parse testParse = constituents[parseIndex];
if (testParse.Label.StartsWith(MaximumEntropyParser.StartPrefix))
{
if (parseIndex == 0)
{
features.Add("endofsentence");
}
break;
}
}
}
return features.ToArray();
}
}
}
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