001/**
002 * Copyright (c) 2011, The University of Southampton and the individual contributors.
003 * All rights reserved.
004 *
005 * Redistribution and use in source and binary forms, with or without modification,
006 * are permitted provided that the following conditions are met:
007 *
008 *   *  Redistributions of source code must retain the above copyright notice,
009 *      this list of conditions and the following disclaimer.
010 *
011 *   *  Redistributions in binary form must reproduce the above copyright notice,
012 *      this list of conditions and the following disclaimer in the documentation
013 *      and/or other materials provided with the distribution.
014 *
015 *   *  Neither the name of the University of Southampton nor the names of its
016 *      contributors may be used to endorse or promote products derived from this
017 *      software without specific prior written permission.
018 *
019 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
020 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
021 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
022 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
023 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
024 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
025 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
026 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
027 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
028 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029 */
030package org.openimaj.data.dataset;
031
032import java.util.Map;
033import java.util.Set;
034
035/**
036 * A {@link Dataset} that is grouped into separate classes or groups. Each group
037 * is represented by a key, and each key corresponds to a sub-dataset.
038 * <p>
039 * Sub-datasets can be any kind of {@link Dataset}, including
040 * {@link GroupedDataset}s, so it is possible to build tree structures.
041 * 
042 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
043 * 
044 * @param <KEY>
045 *            Type of dataset class key
046 * @param <DATASET>
047 *            Type of sub-datasets.
048 * @param <INSTANCE>
049 *            Type of instances in the dataset
050 */
051public interface GroupedDataset<KEY extends Object, DATASET extends Dataset<INSTANCE>, INSTANCE>
052                extends
053                Dataset<INSTANCE>, Map<KEY, DATASET>
054{
055        /**
056         * Get sub-dataset corresponding to the given group key
057         * 
058         * @param key
059         *            the key.
060         * @return the sub dataset, or null if the key was unknown
061         */
062        public DATASET getInstances(KEY key);
063
064        /**
065         * Get the set of all defined group keys.
066         * 
067         * @return the the set of all defined group keys.
068         */
069        public Set<KEY> getGroups();
070
071        /**
072         * Get a random instance from the sub-dataset corresponding to a specific
073         * group.
074         * 
075         * @param key
076         *            the group key
077         * @return a random item from the group.
078         */
079        public INSTANCE getRandomInstance(KEY key);
080}