001/* 
002 * Copyright (c) 2013, Regents of the University of Colorado 
003 * All rights reserved.
004 * 
005 * Redistribution and use in source and binary forms, with or without
006 * modification, are permitted provided that the following conditions are met:
007 * 
008 * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 
009 * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. 
010 * Neither the name of the University of Colorado at Boulder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission. 
011 * 
012 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
013 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
014 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
015 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
016 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
017 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
018 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
019 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
020 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
021 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
022 * POSSIBILITY OF SUCH DAMAGE. 
023 */
024package org.cleartk.ml.chunking;
025
026import java.util.HashMap;
027import java.util.List;
028import java.util.Map;
029
030import org.apache.uima.cas.Feature;
031import org.apache.uima.fit.util.JCasUtil;
032import org.apache.uima.jcas.JCas;
033import org.apache.uima.jcas.tcas.Annotation;
034
035/**
036 * Chunking with Begin-Inside-End-Singleton-Outside labels.
037 * 
038 * Also known as BILOU (Begin-Inside-Last-Outside-Unit) and IOBES
039 * (Inside-Outside-Begin-End-Singleton).
040 * 
041 * <br>
042 * Copyright (c) 2013, Regents of the University of Colorado <br>
043 * All rights reserved.
044 * 
045 * @author Alexey V Romanov
046 * @author Steven Bethard
047 */
048public class BiesoChunking<SUB_CHUNK_TYPE extends Annotation, CHUNK_TYPE extends Annotation>
049    extends Chunking_ImplBase<SUB_CHUNK_TYPE, CHUNK_TYPE> {
050
051  public BiesoChunking(
052      Class<? extends SUB_CHUNK_TYPE> subChunkClass,
053      Class<? extends CHUNK_TYPE> chunkClass) {
054    super(subChunkClass, chunkClass, null);
055  }
056
057  public BiesoChunking(
058      Class<? extends SUB_CHUNK_TYPE> subChunkClass,
059      Class<? extends CHUNK_TYPE> chunkClass,
060      String featureName) {
061    super(subChunkClass, chunkClass, featureName);
062  }
063
064  @Override
065  protected Map<SUB_CHUNK_TYPE, String> getSubChunkToOutcomeMap(
066      JCas jCas,
067      List<SUB_CHUNK_TYPE> chunkComponents,
068      List<CHUNK_TYPE> chunks) {
069    Feature feature = this.getFeature(jCas);
070    Map<SUB_CHUNK_TYPE, String> subChunkToOutcome = new HashMap<SUB_CHUNK_TYPE, String>();
071    for (CHUNK_TYPE chunk : chunks) {
072      String suffix = this.getOutcomeSuffix(chunk, feature);
073      List<? extends SUB_CHUNK_TYPE> subChunks = JCasUtil.selectCovered(this.subChunkClass, chunk);
074      int nSubChunks = subChunks.size();
075      if (nSubChunks == 1) {
076        subChunkToOutcome.put(subChunks.get(0), "S" + suffix);
077      } else {
078        for (int i = 0; i < nSubChunks; ++i) {
079          SUB_CHUNK_TYPE subChunk = subChunks.get(i);
080          if (i == 0) {
081            subChunkToOutcome.put(subChunk, "B" + suffix);
082          } else if (i == nSubChunks - 1) {
083            subChunkToOutcome.put(subChunk, "E" + suffix);
084          } else {
085            subChunkToOutcome.put(subChunk, "I" + suffix);
086          }
087        }
088      }
089    }
090    return subChunkToOutcome;
091  }
092
093  @Override
094  protected boolean isEndOfChunk(
095      char currPrefix,
096      String currLabel,
097      char nextPrefix,
098      String nextLabel) {
099    return currPrefix == 'E' || currPrefix == 'S' || nextPrefix == 'O' || nextPrefix == 'B'
100        || !nextLabel.equals(currLabel);
101  }
102}