[518] | 1 | package de.ugoe.cs.quest.usageprofiles;
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| 2 |
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| 3 | import java.io.Serializable;
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| 4 | import java.security.InvalidParameterException;
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| 5 | import java.util.Collection;
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| 6 | import java.util.HashSet;
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| 7 | import java.util.LinkedHashSet;
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| 8 | import java.util.LinkedList;
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| 9 | import java.util.List;
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| 10 |
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| 11 | import de.ugoe.cs.util.StringTools;
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| 12 |
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| 13 | import edu.uci.ics.jung.graph.DelegateTree;
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| 14 | import edu.uci.ics.jung.graph.Graph;
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| 15 | import edu.uci.ics.jung.graph.Tree;
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| 16 |
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| 17 | /**
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| 18 | * <p>
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| 19 | * This class implements a <it>trie</it>, i.e., a tree of sequences that the
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| 20 | * occurence of subsequences up to a predefined length. This length is the trie
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| 21 | * order.
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| 22 | * </p>
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| 23 | *
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| 24 | * @author Steffen Herbold
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| 25 | *
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| 26 | * @param <T>
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| 27 | * Type of the symbols that are stored in the trie.
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| 28 | *
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| 29 | * @see TrieNode
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| 30 | */
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| 31 | public class Trie<T> implements IDotCompatible, Serializable {
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| 32 |
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| 33 | /**
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| 34 | * <p>
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| 35 | * Id for object serialization.
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| 36 | * </p>
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| 37 | */
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| 38 | private static final long serialVersionUID = 1L;
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| 39 |
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| 40 | /**
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| 41 | * <p>
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| 42 | * Collection of all symbols occuring in the trie.
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| 43 | * </p>
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| 44 | */
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| 45 | private Collection<T> knownSymbols;
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| 46 |
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| 47 | /**
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| 48 | * <p>
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| 49 | * Reference to the root of the trie.
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| 50 | * </p>
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| 51 | */
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| 52 | private final TrieNode<T> rootNode;
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| 53 |
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| 54 | /**
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| 55 | * <p>
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| 56 | * Contructor. Creates a new Trie.
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| 57 | * </p>
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| 58 | */
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| 59 | public Trie() {
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| 60 | rootNode = new TrieNode<T>();
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| 61 | knownSymbols = new LinkedHashSet<T>();
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| 62 | }
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| 63 |
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| 64 | /**
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| 65 | * <p>
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| 66 | * Copy-Constructor. Creates a new Trie as the copy of other. The other trie
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| 67 | * must noch be null.
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| 68 | * </p>
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| 69 | *
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| 70 | * @param other
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| 71 | * Trie that is copied
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| 72 | */
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| 73 | public Trie(Trie<T> other) {
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| 74 | if (other == null) {
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| 75 | throw new InvalidParameterException("other trie must not be null");
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| 76 | }
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| 77 | rootNode = new TrieNode<T>(other.rootNode);
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| 78 | knownSymbols = new LinkedHashSet<T>(other.knownSymbols);
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| 79 | }
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| 80 |
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| 81 | /**
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| 82 | * <p>
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| 83 | * Returns a collection of all symbols occuring in the trie.
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| 84 | * </p>
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| 85 | *
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| 86 | * @return symbols occuring in the trie
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| 87 | */
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| 88 | public Collection<T> getKnownSymbols() {
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| 89 | return new LinkedHashSet<T>(knownSymbols);
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| 90 | }
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| 91 |
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| 92 | /**
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| 93 | * <p>
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| 94 | * Trains the current trie using the given sequence and adds all subsequence
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| 95 | * of length {@code maxOrder}.
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| 96 | * </p>
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| 97 | *
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| 98 | * @param sequence
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| 99 | * sequence whose subsequences are added to the trie
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| 100 | * @param maxOrder
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| 101 | * maximum length of the subsequences added to the trie
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| 102 | */
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| 103 | public void train(List<T> sequence, int maxOrder) {
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| 104 | if (maxOrder < 1) {
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| 105 | return;
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| 106 | }
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| 107 | IncompleteMemory<T> latestActions = new IncompleteMemory<T>(maxOrder);
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| 108 | int i = 0;
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| 109 | for (T currentEvent : sequence) {
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| 110 | latestActions.add(currentEvent);
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| 111 | knownSymbols.add(currentEvent);
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| 112 | i++;
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| 113 | if (i >= maxOrder) {
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| 114 | add(latestActions.getLast(maxOrder));
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| 115 | }
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| 116 | }
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| 117 | int sequenceLength = sequence.size();
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| 118 | for (int j = maxOrder - 1; j > 0; j--) {
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| 119 | add(sequence.subList(sequenceLength - j, sequenceLength));
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| 120 | }
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| 121 | }
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| 122 |
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| 123 | /**
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| 124 | * <p>
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| 125 | * Adds a given subsequence to the trie and increases the counters
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| 126 | * accordingly.
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| 127 | * </p>
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| 128 | *
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| 129 | * @param subsequence
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| 130 | * subsequence whose counters are increased
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| 131 | * @see TrieNode#add(List)
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| 132 | */
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| 133 | protected void add(List<T> subsequence) {
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| 134 | if (subsequence != null && !subsequence.isEmpty()) {
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| 135 | knownSymbols.addAll(subsequence);
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| 136 | subsequence = new LinkedList<T>(subsequence); // defensive copy!
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| 137 | T firstSymbol = subsequence.get(0);
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| 138 | TrieNode<T> node = getChildCreate(firstSymbol);
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| 139 | node.add(subsequence);
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| 140 | }
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| 141 | }
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| 142 |
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| 143 | /**
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| 144 | * <p>
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| 145 | * Returns the child of the root node associated with the given symbol or
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| 146 | * creates it if it does not exist yet.
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| 147 | * </p>
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| 148 | *
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| 149 | * @param symbol
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| 150 | * symbol whose node is required
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| 151 | * @return node associated with the symbol
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| 152 | * @see TrieNode#getChildCreate(Object)
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| 153 | */
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| 154 | protected TrieNode<T> getChildCreate(T symbol) {
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| 155 | return rootNode.getChildCreate(symbol);
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| 156 | }
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| 157 |
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| 158 | /**
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| 159 | * <p>
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| 160 | * Returns the child of the root node associated with the given symbol or
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| 161 | * null if it does not exist.
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| 162 | * </p>
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| 163 | *
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| 164 | * @param symbol
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| 165 | * symbol whose node is required
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| 166 | * @return node associated with the symbol; null if no such node exists
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| 167 | * @see TrieNode#getChild(Object)
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| 168 | */
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| 169 | protected TrieNode<T> getChild(T symbol) {
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| 170 | return rootNode.getChild(symbol);
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| 171 | }
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| 172 |
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| 173 | /**
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| 174 | * <p>
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| 175 | * Returns the number of occurences of the given sequence.
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| 176 | * </p>
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| 177 | *
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| 178 | * @param sequence
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| 179 | * sequence whose number of occurences is required
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| 180 | * @return number of occurences of the sequence
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| 181 | */
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| 182 | public int getCount(List<T> sequence) {
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| 183 | int count = 0;
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| 184 | TrieNode<T> node = find(sequence);
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| 185 | if (node != null) {
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| 186 | count = node.getCount();
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| 187 | }
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| 188 | return count;
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| 189 | }
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| 190 |
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| 191 | /**
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| 192 | * <p>
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| 193 | * Returns the number of occurences of the given prefix and a symbol that
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| 194 | * follows it.<br>
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| 195 | * Convenience function to simplify usage of {@link #getCount(List)}.
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| 196 | * </p>
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| 197 | *
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| 198 | * @param sequence
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| 199 | * prefix of the sequence
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| 200 | * @param follower
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| 201 | * suffix of the sequence
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| 202 | * @return number of occurences of the sequence
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| 203 | * @see #getCount(List)
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| 204 | */
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| 205 | public int getCount(List<T> sequence, T follower) {
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| 206 | List<T> tmpSequence = new LinkedList<T>(sequence);
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| 207 | tmpSequence.add(follower);
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| 208 | return getCount(tmpSequence);
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| 209 |
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| 210 | }
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| 211 |
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| 212 | /**
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| 213 | * <p>
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| 214 | * Searches the trie for a given sequence and returns the node associated
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| 215 | * with the sequence or null if no such node is found.
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| 216 | * </p>
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| 217 | *
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| 218 | * @param sequence
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| 219 | * sequence that is searched for
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| 220 | * @return node associated with the sequence
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| 221 | * @see TrieNode#find(List)
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| 222 | */
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| 223 | public TrieNode<T> find(List<T> sequence) {
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| 224 | if (sequence == null || sequence.isEmpty()) {
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| 225 | return rootNode;
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| 226 | }
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| 227 | List<T> sequenceCopy = new LinkedList<T>(sequence);
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| 228 | TrieNode<T> result = null;
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| 229 | TrieNode<T> node = getChild(sequenceCopy.get(0));
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| 230 | if (node != null) {
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| 231 | sequenceCopy.remove(0);
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| 232 | result = node.find(sequenceCopy);
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| 233 | }
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| 234 | return result;
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| 235 | }
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| 236 |
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| 237 | /**
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| 238 | * <p>
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| 239 | * Returns a collection of all symbols that follow a given sequence in the
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| 240 | * trie. In case the sequence is not found or no symbols follow the sequence
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| 241 | * the result will be empty.
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| 242 | * </p>
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| 243 | *
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| 244 | * @param sequence
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| 245 | * sequence whose followers are returned
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| 246 | * @return symbols following the given sequence
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| 247 | * @see TrieNode#getFollowingSymbols()
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| 248 | */
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| 249 | public Collection<T> getFollowingSymbols(List<T> sequence) {
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| 250 | Collection<T> result = new LinkedList<T>();
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| 251 | TrieNode<T> node = find(sequence);
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| 252 | if (node != null) {
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| 253 | result = node.getFollowingSymbols();
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| 254 | }
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| 255 | return result;
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| 256 | }
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| 257 |
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| 258 | /**
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| 259 | * <p>
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| 260 | * Returns the longest suffix of the given context that is contained in the
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| 261 | * tree and whose children are leaves.
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| 262 | * </p>
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| 263 | *
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| 264 | * @param context
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| 265 | * context whose suffix is searched for
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| 266 | * @return longest suffix of the context
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| 267 | */
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| 268 | public List<T> getContextSuffix(List<T> context) {
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| 269 | List<T> contextSuffix;
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| 270 | if (context != null) {
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| 271 | contextSuffix = new LinkedList<T>(context); // defensive copy
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| 272 | } else {
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| 273 | contextSuffix = new LinkedList<T>();
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| 274 | }
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| 275 | boolean suffixFound = false;
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| 276 |
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| 277 | while (!suffixFound) {
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| 278 | if (contextSuffix.isEmpty()) {
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| 279 | suffixFound = true; // suffix is the empty word
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| 280 | } else {
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| 281 | TrieNode<T> node = find(contextSuffix);
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| 282 | if (node != null) {
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| 283 | if (!node.getFollowingSymbols().isEmpty()) {
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| 284 | suffixFound = true;
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| 285 | }
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| 286 | }
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| 287 | if (!suffixFound) {
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| 288 | contextSuffix.remove(0);
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| 289 | }
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| 290 | }
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| 291 | }
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| 292 |
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| 293 | return contextSuffix;
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| 294 | }
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| 295 |
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| 296 | /**
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| 297 | * <p>
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| 298 | * Helper class for graph visualization of a trie.
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| 299 | * </p>
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| 300 | *
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| 301 | * @author Steffen Herbold
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| 302 | * @version 1.0
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| 303 | */
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| 304 | static public class Edge {
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| 305 | }
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| 306 |
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| 307 | /**
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| 308 | * <p>
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| 309 | * Helper class for graph visualization of a trie.
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| 310 | * </p>
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| 311 | *
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| 312 | * @author Steffen Herbold
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| 313 | * @version 1.0
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| 314 | */
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| 315 | static public class TrieVertex {
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| 316 |
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| 317 | /**
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| 318 | * <p>
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| 319 | * Id of the vertex.
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| 320 | * </p>
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| 321 | */
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| 322 | private String id;
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| 323 |
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| 324 | /**
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| 325 | * <p>
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| 326 | * Contructor. Creates a new TrieVertex.
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| 327 | * </p>
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| 328 | *
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| 329 | * @param id
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| 330 | * id of the vertex
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| 331 | */
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| 332 | protected TrieVertex(String id) {
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| 333 | this.id = id;
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| 334 | }
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| 335 |
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| 336 | /**
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| 337 | * <p>
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| 338 | * Returns the id of the vertex.
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| 339 | * </p>
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| 340 | *
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| 341 | * @see java.lang.Object#toString()
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| 342 | */
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| 343 | @Override
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| 344 | public String toString() {
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| 345 | return id;
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| 346 | }
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| 347 | }
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| 348 |
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| 349 | /**
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| 350 | * <p>
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| 351 | * Returns a {@link Graph} representation of the trie.
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| 352 | * </p>
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| 353 | *
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| 354 | * @return {@link Graph} representation of the trie
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| 355 | */
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| 356 | protected Tree<TrieVertex, Edge> getGraph() {
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| 357 | DelegateTree<TrieVertex, Edge> graph = new DelegateTree<TrieVertex, Edge>();
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| 358 | rootNode.getGraph(null, graph);
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| 359 | return graph;
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| 360 | }
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| 361 |
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| 362 | /*
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| 363 | * (non-Javadoc)
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| 364 | *
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| 365 | * @see de.ugoe.cs.quest.usageprofiles.IDotCompatible#getDotRepresentation()
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| 366 | */
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| 367 | public String getDotRepresentation() {
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| 368 | StringBuilder stringBuilder = new StringBuilder();
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| 369 | stringBuilder.append("digraph model {" + StringTools.ENDLINE);
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| 370 | rootNode.appendDotRepresentation(stringBuilder);
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| 371 | stringBuilder.append('}' + StringTools.ENDLINE);
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| 372 | return stringBuilder.toString();
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| 373 | }
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| 374 |
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| 375 | /**
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| 376 | * <p>
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| 377 | * Returns the string representation of the root node.
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| 378 | * </p>
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| 379 | *
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| 380 | * @see TrieNode#toString()
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| 381 | * @see java.lang.Object#toString()
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| 382 | */
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| 383 | @Override
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| 384 | public String toString() {
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| 385 | return rootNode.toString();
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| 386 | }
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| 387 |
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| 388 | /**
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| 389 | * <p>
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| 390 | * Returns the number of symbols contained in the trie.
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| 391 | * </p>
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| 392 | *
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| 393 | * @return number of symbols contained in the trie
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| 394 | */
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| 395 | public int getNumSymbols() {
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| 396 | return knownSymbols.size();
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| 397 | }
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| 398 |
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| 399 | /**
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| 400 | * <p>
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| 401 | * Returns the number of trie nodes that are ancestors of a leaf. This is
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| 402 | * the equivalent to the number of states a first-order markov model would
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| 403 | * have.
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| 404 | * <p>
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| 405 | *
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| 406 | * @return number of trie nodes that are ancestors of leafs.
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| 407 | */
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| 408 | public int getNumLeafAncestors() {
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| 409 | List<TrieNode<T>> ancestors = new LinkedList<TrieNode<T>>();
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| 410 | rootNode.getLeafAncestors(ancestors);
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| 411 | return ancestors.size();
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| 412 | }
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| 413 |
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| 414 | /**
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| 415 | * <p>
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| 416 | * Returns the number of trie nodes that are leafs.
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| 417 | * </p>
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| 418 | *
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| 419 | * @return number of leafs in the trie
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| 420 | */
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| 421 | public int getNumLeafs() {
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| 422 | return rootNode.getNumLeafs();
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| 423 | }
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| 424 |
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| 425 | /**
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| 426 | * <p>
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| 427 | * Updates the list of known symbols by replacing it with all symbols that
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| 428 | * are found in the child nodes of the root node. This should be the same as
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| 429 | * all symbols that are contained in the trie.
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| 430 | * </p>
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| 431 | */
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| 432 | public void updateKnownSymbols() {
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| 433 | knownSymbols = new HashSet<T>();
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| 434 | for (TrieNode<T> node : rootNode.getChildren()) {
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| 435 | knownSymbols.add(node.getSymbol());
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| 436 | }
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| 437 | }
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| 438 |
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| 439 | /**
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| 440 | * <p>
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| 441 | * Two Tries are defined as equal, if their {@link #rootNode} are equal.
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| 442 | * </p>
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| 443 | *
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| 444 | * @see java.lang.Object#equals(java.lang.Object)
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| 445 | */
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| 446 | @SuppressWarnings("rawtypes")
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| 447 | @Override
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| 448 | public boolean equals(Object other) {
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| 449 | if (other == this) {
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| 450 | return true;
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| 451 | }
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| 452 | if (other instanceof Trie) {
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| 453 | return rootNode.equals(((Trie) other).rootNode);
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| 454 | }
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| 455 | return false;
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| 456 | }
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| 457 |
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| 458 | /*
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| 459 | * (non-Javadoc)
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| 460 | *
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| 461 | * @see java.lang.Object#hashCode()
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| 462 | */
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| 463 | @Override
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| 464 | public int hashCode() {
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| 465 | int multiplier = 17;
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| 466 | int hash = 42;
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| 467 | if (rootNode != null) {
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| 468 | hash = multiplier * hash + rootNode.hashCode();
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| 469 | }
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| 470 | return hash;
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| 471 | }
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| 472 | }
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