001/** 
002 * Copyright (c) 2012, 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 */
024
025package org.cleartk.ml.feature.transform;
026
027import java.io.IOException;
028import java.net.URI;
029
030import org.cleartk.ml.Instance;
031
032/**
033 * Copyright (c) 2012, Regents of the University of Colorado <br>
034 * All rights reserved.
035 * <p>
036 * TrainableExtractors defines a extractors that can be trained to fix up data based on a set of
037 * instances. Prototypical cases include computing statistics for normalization such as mean,
038 * standard deviation, min, max, or for computing corpus tf*idf values
039 * 
040 * <p>
041 * TrainableExtractors that have not yet been trained cannot be used as subextractors inside of any
042 * other feature extractor, though they can have subextractors of their own. So for example, while
043 * the following will work:
044 * <p>
045 * 
046 * <code>
047 * new TfidfExtractor(new ContextExtractor<Token>(Token.class, new CoveredTextExtractor(), new
048 * Preceding(2)))
049 * </code>
050 * <p>
051 * the following will not:
052 * <p>
053 * <code>
054 * new ContextExtractor<Token>(Token.class, new TfidfExtractor(new CoveredTextExtractor()), new
055 * Preceding(2))
056 * </code>
057 */
058public interface TrainableExtractor<OUTCOME_T> {
059
060  /**
061   * In the prototypical case, train takes a collection of instances and computes statistics over
062   * the values such as computing mean, standard deviation, TF*IDF, etc...
063   * 
064   * @param instances
065   *          - URI pointing to the output location for saving statistics
066   */
067  public void train(Iterable<Instance<OUTCOME_T>> instances);
068
069  /**
070   * Saves statistics from train in location URI
071   */
072  public void save(URI uri) throws IOException;
073
074  /**
075   * Loads statistics from location URI
076   */
077  public void load(URI uri) throws IOException;
078
079  /**
080   * Transforms all features handled by this extractor. Called on an Instance that was created
081   * before {@link #train(Iterable)} was called, to complete the processing of the Instance.
082   * 
083   * @param instance
084   *          An instance that was created before {@link #train(Iterable)} was called.
085   * @return A copy of the instance, where processing of the instances is complete.
086   */
087  public Instance<OUTCOME_T> transform(Instance<OUTCOME_T> instance);
088
089}