1 | package de.ugoe.cs.quest.usageprofiles;
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2 |
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3 | import java.util.ArrayList;
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4 | import java.util.Collection;
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5 | import java.util.HashSet;
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6 | import java.util.LinkedHashSet;
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7 | import java.util.LinkedList;
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8 | import java.util.List;
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9 | import java.util.Random;
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10 | import java.util.Set;
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11 |
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12 | import de.ugoe.cs.quest.eventcore.Event;
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13 | import de.ugoe.cs.quest.usageprofiles.Trie.Edge;
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14 | import de.ugoe.cs.quest.usageprofiles.Trie.TrieVertex;
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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 | * Implements a skeleton for stochastic processes that can calculate probabilities based on a trie.
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20 | * The skeleton provides all functionalities of {@link IStochasticProcess} except
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21 | * {@link IStochasticProcess#getProbability(List, Event)}.
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22 | * </p>
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23 | *
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24 | * @author Steffen Herbold
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25 | * @version 1.0
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26 | */
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27 | public abstract class TrieBasedModel implements IStochasticProcess {
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28 |
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29 | /**
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30 | * <p>
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31 | * Id for object serialization.
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32 | * </p>
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33 | */
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34 | private static final long serialVersionUID = 1L;
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35 |
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36 | /**
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37 | * <p>
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38 | * The order of the trie, i.e., the maximum length of subsequences stored in the trie.
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39 | * </p>
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40 | */
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41 | protected int trieOrder;
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42 |
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43 | /**
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44 | * <p>
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45 | * Trie on which the probability calculations are based.
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46 | * </p>
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47 | */
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48 | protected Trie<Event> trie = null;
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49 |
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50 | /**
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51 | * <p>
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52 | * Random number generator used by probabilistic sequence generation methods.
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53 | * </p>
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54 | */
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55 | protected final Random r;
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56 |
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57 | /**
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58 | * <p>
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59 | * Constructor. Creates a new TrieBasedModel that can be used for stochastic processes with a
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60 | * Markov order less than or equal to {@code markovOrder}.
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61 | * </p>
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62 | *
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63 | * @param markovOrder
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64 | * Markov order of the model
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65 | * @param r
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66 | * random number generator used by probabilistic methods of the class
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67 | * @throws IllegalArgumentException
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68 | * thrown if markovOrder is less than 0 or the random number generator r is null
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69 | */
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70 | public TrieBasedModel(int markovOrder, Random r) {
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71 | super();
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72 | if (markovOrder < 0) {
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73 | throw new IllegalArgumentException("markov order must not be less than 0");
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74 | }
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75 | if (r == null) {
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76 | throw new IllegalArgumentException("random number generator r must not be null");
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77 | }
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78 | this.trieOrder = markovOrder + 1;
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79 | this.r = r;
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80 | }
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81 |
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82 | /**
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83 | * <p>
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84 | * Trains the model by generating a trie from which probabilities are calculated. The trie is
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85 | * newly generated based solely on the passed sequences. If an existing model should only be
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86 | * updated, use {@link #update(Collection)} instead.
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87 | * </p>
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88 | *
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89 | * @param sequences
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90 | * training data
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91 | * @throws IllegalArgumentException
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92 | * thrown is sequences is null
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93 | */
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94 | public void train(Collection<List<Event>> sequences) {
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95 | trie = null;
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96 | update(sequences);
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97 | }
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98 |
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99 | /**
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100 | * <p>
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101 | * Trains the model by updating the trie from which the probabilities are calculated. This
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102 | * function updates an existing trie. In case no trie exists yet, a new trie is generated and
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103 | * the function behaves like {@link #train(Collection)}.
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104 | * </p>
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105 | *
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106 | * @param sequences
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107 | * training data
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108 | * @throws IllegalArgumentException
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109 | * thrown is sequences is null
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110 | */
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111 | public void update(Collection<List<Event>> sequences) {
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112 | if (sequences == null) {
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113 | throw new IllegalArgumentException("sequences must not be null");
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114 | }
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115 | if (trie == null) {
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116 | trie = new Trie<Event>();
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117 | }
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118 | for (List<Event> sequence : sequences) {
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119 | List<Event> currentSequence = new LinkedList<Event>(sequence); // defensive
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120 | // copy
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121 | currentSequence.add(0, Event.STARTEVENT);
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122 | currentSequence.add(Event.ENDEVENT);
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123 |
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124 | trie.train(currentSequence, trieOrder);
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125 | }
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126 | }
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127 |
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128 | /*
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129 | * (non-Javadoc)
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130 | *
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131 | * @see de.ugoe.cs.quest.usageprofiles.IStochasticProcess#randomSequence()
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132 | */
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133 | @Override
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134 | public List<Event> randomSequence() {
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135 | return randomSequence(Integer.MAX_VALUE, true);
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136 | }
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137 |
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138 | /*
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139 | * (non-Javadoc)
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140 | *
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141 | * @see de.ugoe.cs.quest.usageprofiles.IStochasticProcess#randomSequence()
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142 | */
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143 | @Override
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144 | public List<Event> randomSequence(int maxLength, boolean validEnd) {
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145 | List<Event> sequence = new LinkedList<Event>();
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146 | if (trie != null) {
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147 | boolean endFound = false;
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148 | while (!endFound) { // outer loop for length checking
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149 | sequence = new LinkedList<Event>();
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150 | IncompleteMemory<Event> context = new IncompleteMemory<Event>(trieOrder - 1);
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151 | context.add(Event.STARTEVENT);
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152 |
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153 | while (!endFound && sequence.size() <= maxLength) {
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154 | double randVal = r.nextDouble();
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155 | double probSum = 0.0;
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156 | List<Event> currentContext = context.getLast(trieOrder);
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157 | for (Event symbol : trie.getKnownSymbols()) {
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158 | probSum += getProbability(currentContext, symbol);
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159 | if (probSum >= randVal) {
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160 | if (!(Event.STARTEVENT.equals(symbol) || Event.ENDEVENT.equals(symbol)))
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161 | {
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162 | // only add the symbol the sequence if it is not
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163 | // START or END
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164 | context.add(symbol);
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165 | sequence.add(symbol);
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166 | }
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167 | endFound =
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168 | (Event.ENDEVENT.equals(symbol)) ||
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169 | (!validEnd && sequence.size() == maxLength);
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170 | break;
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171 | }
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172 | }
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173 | }
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174 | }
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175 | }
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176 | return sequence;
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177 | }
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178 |
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179 | /**
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180 | * <p>
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181 | * Returns a Dot representation of the internal trie.
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182 | * </p>
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183 | *
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184 | * @return dot representation of the internal trie
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185 | */
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186 | public String getTrieDotRepresentation() {
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187 | if (trie == null) {
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188 | return "";
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189 | }
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190 | else {
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191 | return trie.getDotRepresentation();
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192 | }
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193 | }
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194 |
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195 | /**
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196 | * <p>
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197 | * Returns a {@link Tree} of the internal trie that can be used for visualization.
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198 | * </p>
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199 | *
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200 | * @return {@link Tree} depicting the internal trie
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201 | */
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202 | public Tree<TrieVertex, Edge> getTrieGraph() {
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203 | if (trie == null) {
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204 | return null;
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205 | }
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206 | else {
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207 | return trie.getGraph();
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208 | }
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209 | }
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210 |
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211 | /**
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212 | * <p>
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213 | * The string representation of the model is {@link Trie#toString()} of {@link #trie}.
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214 | * </p>
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215 | *
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216 | * @see java.lang.Object#toString()
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217 | */
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218 | @Override
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219 | public String toString() {
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220 | if (trie == null) {
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221 | return "";
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222 | }
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223 | else {
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224 | return trie.toString();
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225 | }
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226 | }
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227 |
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228 | /*
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229 | * (non-Javadoc)
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230 | *
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231 | * @see de.ugoe.cs.quest.usageprofiles.IStochasticProcess#getNumStates()
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232 | */
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233 | @Override
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234 | public int getNumSymbols() {
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235 | if (trie == null) {
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236 | return 0;
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237 | }
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238 | else {
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239 | return trie.getNumSymbols();
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240 | }
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241 | }
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242 |
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243 | /*
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244 | * (non-Javadoc)
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245 | *
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246 | * @see de.ugoe.cs.quest.usageprofiles.IStochasticProcess#getStateStrings()
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247 | */
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248 | @Override
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249 | public String[] getSymbolStrings() {
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250 | if (trie == null) {
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251 | return new String[0];
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252 | }
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253 | String[] stateStrings = new String[getNumSymbols()];
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254 | int i = 0;
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255 | for (Event symbol : trie.getKnownSymbols()) {
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256 | if (symbol.toString() == null) {
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257 | stateStrings[i] = "null";
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258 | }
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259 | else {
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260 | stateStrings[i] = symbol.toString();
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261 | }
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262 | i++;
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263 | }
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264 | return stateStrings;
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265 | }
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266 |
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267 | /*
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268 | * (non-Javadoc)
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269 | *
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270 | * @see de.ugoe.cs.quest.usageprofiles.IStochasticProcess#getEvents()
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271 | */
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272 | @Override
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273 | public Collection<Event> getEvents() {
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274 | if (trie == null) {
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275 | return new HashSet<Event>();
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276 | }
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277 | else {
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278 | return trie.getKnownSymbols();
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279 | }
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280 | }
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281 |
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282 | /*
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283 | * (non-Javadoc)
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284 | *
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285 | * @see de.ugoe.cs.quest.usageprofiles.IStochasticProcess#generateSequences(int)
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286 | */
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287 | @Override
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288 | public Collection<List<Event>> generateSequences(int length) {
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289 | return generateSequences(length, false);
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290 | }
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291 |
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292 | /*
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293 | * (non-Javadoc)
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294 | *
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295 | * @see de.ugoe.cs.quest.usageprofiles.IStochasticProcess#generateSequences(int, boolean)
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296 | */
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297 | @Override
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298 | public Set<List<Event>> generateSequences(int length, boolean fromStart) {
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299 | Set<List<Event>> sequenceSet = new LinkedHashSet<List<Event>>();
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300 | if (length < 1) {
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301 | throw new IllegalArgumentException(
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302 | "Length of generated subsequences must be at least 1.");
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303 | }
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304 | if (length == 1) {
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305 | if (fromStart) {
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306 | List<Event> subSeq = new LinkedList<Event>();
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307 | subSeq.add(Event.STARTEVENT);
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308 | sequenceSet.add(subSeq);
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309 | }
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310 | else {
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311 | for (Event event : getEvents()) {
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312 | List<Event> subSeq = new LinkedList<Event>();
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313 | subSeq.add(event);
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314 | sequenceSet.add(subSeq);
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315 | }
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316 | }
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317 | return sequenceSet;
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318 | }
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319 | Collection<Event> events = getEvents();
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320 | Collection<List<Event>> seqsShorter = generateSequences(length - 1, fromStart);
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321 | for (Event event : events) {
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322 | for (List<Event> seqShorter : seqsShorter) {
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323 | Event lastEvent = event;
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324 | if (getProbability(seqShorter, lastEvent) > 0.0) {
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325 | List<Event> subSeq = new ArrayList<Event>(seqShorter);
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326 | subSeq.add(lastEvent);
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327 | sequenceSet.add(subSeq);
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328 | }
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329 | }
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330 | }
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331 | return sequenceSet;
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332 | }
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333 |
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334 | /*
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335 | * (non-Javadoc)
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336 | *
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337 | * @see de.ugoe.cs.quest.usageprofiles.IStochasticProcess#generateValidSequences (int)
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338 | */
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339 | @Override
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340 | public Collection<List<Event>> generateValidSequences(int length) {
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341 | // check for min-length implicitly done by generateSequences
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342 | Collection<List<Event>> allSequences = generateSequences(length, true);
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343 | Collection<List<Event>> validSequences = new LinkedHashSet<List<Event>>();
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344 | for (List<Event> sequence : allSequences) {
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345 | if (sequence.size() == length &&
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346 | Event.ENDEVENT.equals(sequence.get(sequence.size() - 1)))
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347 | {
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348 | validSequences.add(sequence);
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349 | }
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350 | }
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351 | return validSequences;
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352 | }
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353 |
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354 | /*
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355 | * (non-Javadoc)
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356 | *
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357 | * @see de.ugoe.cs.quest.usageprofiles.IStochasticProcess#getProbability(java.util .List)
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358 | */
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359 | @Override
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360 | public double getProbability(List<Event> sequence) {
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361 | if (sequence == null) {
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362 | throw new IllegalArgumentException("sequence must not be null");
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363 | }
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364 | double prob = 1.0;
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365 | List<Event> context = new LinkedList<Event>();
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366 | for (Event event : sequence) {
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367 | prob *= getProbability(context, event);
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368 | context.add(event);
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369 | }
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370 | return prob;
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371 | }
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372 |
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373 | /*
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374 | * (non-Javadoc)
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375 | *
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376 | * @see de.ugoe.cs.quest.usageprofiles.IStochasticProcess#getNumFOMStates()
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377 | */
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378 | @Override
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379 | public int getNumFOMStates() {
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380 | if (trie == null) {
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381 | return 0;
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382 | }
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383 | else {
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384 | return trie.getNumLeafAncestors();
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385 | }
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386 | }
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387 |
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388 | /*
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389 | * (non-Javadoc)
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390 | *
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391 | * @see de.ugoe.cs.quest.usageprofiles.IStochasticProcess#getNumTransitions()
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392 | */
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393 | @Override
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394 | public int getNumTransitions() {
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395 | if (trie == null) {
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396 | return 0;
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397 | }
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398 | else {
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399 | return trie.getNumLeafs();
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400 | }
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401 | }
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402 | }
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