AbstractionCreator_Qualitative.java

package ca.pfv.spmf.algorithms.sequentialpatterns.clasp_AGP.dataStructures.creators;

import java.util.ArrayList;
import java.util.List;

import ca.pfv.spmf.algorithms.sequentialpatterns.clasp_AGP.dataStructures.Item;
import ca.pfv.spmf.algorithms.sequentialpatterns.clasp_AGP.dataStructures.abstracciones.Abstraction_Generic;
import ca.pfv.spmf.algorithms.sequentialpatterns.clasp_AGP.dataStructures.abstracciones.Abstraction_Qualitative;
import ca.pfv.spmf.algorithms.sequentialpatterns.clasp_AGP.dataStructures.abstracciones.ItemAbstractionPair;
import ca.pfv.spmf.algorithms.sequentialpatterns.clasp_AGP.dataStructures.patterns.Pattern;
import ca.pfv.spmf.algorithms.sequentialpatterns.clasp_AGP.dataStructures.patterns.PatternCreator;

/**
 * Class that implements a qualitative abstraction. Two different values are
 * possible: to be with an equal relation with respect to a previous pair (if
 * occurs at the same time), or to be with an after relation with respect to
 * that previous pair (the previous pair have a before relation with respect to
 * this one)
 *
 * Copyright Antonio Gomariz Peñalver 2013
 *
 * This file is part of the SPMF DATA MINING SOFTWARE
 * (http://www.philippe-fournier-viger.com/spmf).
 *
 * SPMF is free software: you can redistribute it and/or modify it under the
 * terms of the GNU General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any later
 * version.
 *
 * SPMF 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * SPMF. If not, see <http://www.gnu.org/licenses/>.
 *
 * @author agomariz
 */
public class AbstractionCreator_Qualitative extends AbstractionCreator {

    private static AbstractionCreator_Qualitative instance = null;

    public static void sclear() {
        instance = null;
    }

    private AbstractionCreator_Qualitative() {
    }

    public static AbstractionCreator_Qualitative getInstance() {
        if (instance == null) {
            instance = new AbstractionCreator_Qualitative();
        }
        return instance;
    }

    /**
     * It creates a default abstraction. The abstraction is established to false
     * @return the abstraction
     */
    @Override
    public Abstraction_Generic createDefaultAbstraction() {
        return Abstraction_Qualitative.create(false);
    }

    /**
     * It creates a relation with the given parameter.
     * @param hasEqualRelation The boolean indicatin if the item has an equal 
     * relation with the previous item in the pattern
     * @return the created relation
     */
    public Abstraction_Generic crearAbstraccion(boolean hasEqualRelation) {
        return Abstraction_Qualitative.create(hasEqualRelation);
    }

    /**
     * It obtains the subpattern that is derived from removing from the given
     * pattern ,the item specified in the position pointed out by the given index 
     * @param extension the pattern
     * @param index the index
     * @return the subpattern
     */
    @Override
    public Pattern getSubpattern(Pattern extension, int index) {
        ItemAbstractionPairCreator pairCreator = ItemAbstractionPairCreator.getInstance();
        PatternCreator patternCreator = PatternCreator.getInstance();
        List<ItemAbstractionPair> subpatternElements = new ArrayList<ItemAbstractionPair>(extension.size() - 1);
        Abstraction_Generic abstraction = null;
        int nextIndex = index + 1;
        for (int i = 0; i < extension.size(); i++) {
            if (i != index) {
                if (i == nextIndex) {
                    if (abstraction == null) {
                        abstraction = extension.getIthElement(i).getAbstraction();
                    }
                    subpatternElements.add(pairCreator.getItemAbstractionPair(extension.getIthElement(i).getItem(), abstraction));
                } else {
                    subpatternElements.add(extension.getIthElement(i));
                }                
            } else {
                if (index == 0) {
                    abstraction = createDefaultAbstraction();
                } else {
                    Abstraction_Qualitative abstraccionDelQuitado = (Abstraction_Qualitative) extension.getIthElement(i).getAbstraction();
                    if (!abstraccionDelQuitado.hasEqualRelation()) {
                        abstraction = crearAbstraccion(false);
                    }
                }
            }
        }
        return patternCreator.createPattern(subpatternElements);
    }

    @Override
    public void clear() {
    }

    /**
     * Method that check if for the two patterns given as parameters, the
     * shortest one is a subpattern of the longest one
     * @param shorter The pattern which we check if is a subpattern of another
     * longer than it
     * @param larger Pattern which we want to check if another pattern is 
     * subpattern of itself
     * @param index index that indicates which position we have to take into account
     * @param positions List of positions of the appearances of the elements of
     * the shorter pattern in the longer one
     * @return true if it is a subpattern, otherwise false
     */
    @Override
    public boolean isSubpattern(Pattern shorter, Pattern larger, int index, List<Integer> positions) {
        //We get the pair indicated by index
        ItemAbstractionPair pair = shorter.getIthElement(index);
        Item itemPair = pair.getItem();
        Abstraction_Generic absPair = pair.getAbstraction();
        
        //And we also get the abstraction that was in the index-1 position
        Abstraction_Generic previousAbs = index > 0 ? shorter.getIthElement(index - 1).getAbstraction() : null;
        //Flag in order to cancel the search
        boolean cancelled = false;
        Integer pos;
        /* While the item index pointed out by the position is less than the 
         * size of the largest pattern
         */
        while (positions.get(index) < larger.size()) {
            /* 
             * We search for the item of the shorter pattern pointed by index in 
             * the longer one
             */
            if (index == 0) {
                pos = searchForFirstAppearance(larger, positions.get(index), itemPair);
            } else {
                pos = findItemPositionInPattern(larger, itemPair, absPair, previousAbs, positions.get(index), positions.get(index - 1));
            }
            //If we found any position
            if (pos != null) {
                //We set it in the array of positions
                positions.set(index, pos);

                //if we are not in the last element of the shorter pattern
                if (index + 1 < shorter.size()) {
                    //We create a new position that is just one position after
                    Integer newPos = increasePosition(positions.get(index));
                    //And we initialize the next index position to that new position
                    positions.set(index + 1, newPos);
                    /* And we make a recursive call to go on checking if shorter
                     * is a subpattern of longer
                     */
                    boolean output = isSubpattern(shorter, larger, index + 1, positions);
                    //If we have found a matching between both patterns
                    if (output) {
                        positions.clear();
                        //we return a true answer
                        return true;
                    }
                } else {//If, conversely, we are in the last element of the shorter pattern
                    /* 
                     * We have already found a matching between shorter and 
                     * longer and we conclude that one is a subpattern of the 
                     * other one
                     */
                    positions.clear();
                    return true;
                }
            } else {//If conversely, we did not find any position for the current index
                //If we are not in the first element of the pattern
                if (index > 0) {
                    /* We increase the itemset position of the previous index in 
                     * order to find other matching elements
                     */
                    int newPos = increaseItemset(larger, positions.get(index - 1));
                    //And we update that position
                    positions.set(index - 1, newPos);
                }
                //We set to to true the flag that indicates the end of the method
                cancelled = true;
                /* 
                 * And break the loop in order to go back and try to find other 
                 * matching elements that makes the subsequence possible
                 */
                break;
            }
        }
        /* If we are finish the loop and not by breaking it, and we are not looking
         * for the first element of the shorter pattern
         */
        if (index > 0 && !cancelled) {
            /* We increase the itemset position of the previous index in order 
             * to find other matching elements
             */
            int newPos = increaseItemset(larger, positions.get(index - 1));
            //And we update that position
            positions.set(index - 1, newPos);
        }
        /* 
         * We return a false value, indicating that we cannot reach a matching 
         * with the current choices of elements in the longer pattern
         */
        return false;
    }

    /**
     * Method that search the first appearance of an item (given as parameter)
     * in a pattern, starting from a beginning index
     * @param p Pattern where we search for an item
     * @param beginning Index from which we start to search from the item
     * @param itemPair Item to search for
     * @return The item position where we found the item, or null if this
     * does not appear
     */
    public Integer searchForFirstAppearance(Pattern p, Integer beginning, Item itemPair) {
        for (int i = beginning; i < p.size(); i++) {
            Item currentItem = p.getIthElement(i).getItem();
            if (currentItem.equals(itemPair)) {
                return i;
            }
        }
        return null;
    }

    /**
     * It searches for a position in the pattern given as parameter where
     * an item, also given as a parameter, appears
     * @param p Pattern where we are going to search for
     * @param itemPair Item to search for
     * @param currentAbs Abstraction of the current element of the pattern 
     * where the item appeared
     * @param previousAbs Astraction of the previous element of the pattern 
     * where the item appeared
     * @param currentPosition Position for the current element
     * @param previousPosition Position of the previous element
     * @return the position
     */
    public Integer findItemPositionInPattern(Pattern p, Item itemPair, Abstraction_Generic currentAbs, Abstraction_Generic previousAbs, Integer currentPosition, Integer previousPosition) {
        Abstraction_Qualitative abs = (Abstraction_Qualitative) currentAbs;
        Integer pos;
        //If the current Abstraction has an equal relation with the previous pair
        if (abs.hasEqualRelation()) {
            //We search for the item in the same itemset where the previous item appeared
            pos = searchForInTheSameItemset(p, itemPair, currentPosition);
        } else {//Otherwise
            //We start keeping the currentPosition
            int positionToSearchFor = currentPosition;
            /* 
             * If the positions of both the current item and the previous one 
             * are not in different itemsets
             */
            if (!areInDifferentItemsets(p, previousPosition, currentPosition)) {
                /*
                 * We increase the position until we get the first element that 
                 * appear in another itemset
                 */
                positionToSearchFor = increaseItemset(p, currentPosition);
            }
            pos = searchForFirstAppearance(p, positionToSearchFor, itemPair);
        }
        return pos;
    }

    /**
     * It increase the position of a given position by 1.
     * @param beginning the position
     * @return the position +1
     */
    public Integer increasePosition(Integer beginning) {
        return beginning + 1;
    }

    /**
     * Increase a position to the first element position where it starts 
     * another itemset
     * @param p Pattern in which we search for the beginning of another itemset
     * @param beginning Index from which we start to search for
     * @return The item index where a new Itemset starts
     */
    public int increaseItemset(Pattern p, Integer beginning) {
        //For all the elements appearing after beginning index
        for (int i = beginning + 1; i < p.size(); i++) {
            ItemAbstractionPair currentPair = p.getIthElement(i);
            Abstraction_Qualitative qualitativeAbs = (Abstraction_Qualitative) currentPair.getAbstraction();
            //If the relation is not an equal relation, then we have changed of itemset
            if (!qualitativeAbs.hasEqualRelation()) {
                //And return the index
                return i;
            }
        }
        /* 
         * If we have got this point that means that we were in the last itemset
         * of the pattern and, therefore, we return the size of the pattern, 
         * since there can not be any index bigger than this value
         */
        return p.size();
    }

    /**
     * Search for an item in the same itemset that the previous one appeared
     * @param pattern Pattern where we are goin to search for the item
     * @param itemPair Item to search for
     * @param beginning Index from which we are going to start to search for
     * @return the index where the item appears, or null if this index does not
     * exist
     */
    private Integer searchForInTheSameItemset(Pattern pattern, Item itemPair, Integer beginning) {
        //From the beginning index and on
        for (int i = beginning; i < pattern.size(); i++) {
            ItemAbstractionPair currentPair = pattern.getIthElement(i);
            Abstraction_Qualitative qualitativeAbstraction = (Abstraction_Qualitative) currentPair.getAbstraction();
            //If the item has not an equal relation
            if (!qualitativeAbstraction.hasEqualRelation()) {
                /*
                 * We have finished without finding the item, since we have 
                 * already change of itemset
                 */
                return null;
            } else {
                /*
                 * If, conversely, there is an equal relation, we check if this 
                 * item is equal to which we are searching for
                 */
                if (currentPair.getItem().equals(itemPair)) {
                    //In that case we return the index position
                    return i;
                }
            }
        }
        return null;
    }

    /**
     * Method that informs if for a pattern, two positions correspond 
     * to a same itemset or not
     * @param pattern Pattern in which we check the two positions
     * @param p1 First position
     * @param p2 Second position
     * @return True if they are in different itemsets, False otherwise
     */
    private boolean areInDifferentItemsets(Pattern pattern, Integer p1, Integer p2) {
        //For all the elements between positions p1 and p2
        for (int i = p1+1; i <= p2 && i < pattern.size(); i++) {
            ItemAbstractionPair currentPair = pattern.getIthElement(i);
            Abstraction_Qualitative qualitativeAbs = (Abstraction_Qualitative) currentPair.getAbstraction();
            /*
             * If the ith element does not have an equal relation, we conclude 
             * that p1 and p2 are not in the same itemset and we can finish
             */
            if(!qualitativeAbs.hasEqualRelation())
                return true;
        }
        //If we get this point that means p1 and p2 are in the same itemset
        return false;
    }
}