1 | // Copyright 2012 Georg-August-Universität Göttingen, Germany
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2 | //
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3 | // Licensed under the Apache License, Version 2.0 (the "License");
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4 | // you may not use this file except in compliance with the License.
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5 | // You may obtain a copy of the License at
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6 | //
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7 | // http://www.apache.org/licenses/LICENSE-2.0
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8 | //
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9 | // Unless required by applicable law or agreed to in writing, software
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10 | // distributed under the License is distributed on an "AS IS" BASIS,
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11 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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12 | // See the License for the specific language governing permissions and
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13 | // limitations under the License.
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14 |
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15 | package de.ugoe.cs.autoquest.usageprofiles;
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16 |
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17 | import java.util.ArrayList;
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18 | import java.util.Collection;
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19 | import java.util.HashSet;
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20 | import java.util.LinkedHashSet;
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21 | import java.util.LinkedList;
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22 | import java.util.List;
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23 | import java.util.Random;
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24 | import java.util.Set;
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25 |
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26 | import de.ugoe.cs.autoquest.eventcore.Event;
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27 | import de.ugoe.cs.autoquest.usageprofiles.Trie.Edge;
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28 | import de.ugoe.cs.autoquest.usageprofiles.Trie.TrieVertex;
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29 | import edu.uci.ics.jung.graph.Tree;
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30 |
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31 | /**
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32 | * <p>
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33 | * Implements a skeleton for stochastic processes that can calculate probabilities based on a trie.
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34 | * The skeleton provides all functionalities of {@link IStochasticProcess} except
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35 | * {@link IStochasticProcess#getProbability(List, Event)}.
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36 | * </p>
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37 | *
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38 | * @author Steffen Herbold
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39 | * @version 1.0
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40 | */
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41 | public abstract class TrieBasedModel implements IStochasticProcess {
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42 |
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43 | /**
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44 | * <p>
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45 | * Id for object serialization.
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46 | * </p>
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47 | */
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48 | private static final long serialVersionUID = 1L;
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49 |
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50 | /**
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51 | * <p>
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52 | * The order of the trie, i.e., the maximum length of subsequences stored in the trie.
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53 | * </p>
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54 | */
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55 | protected int trieOrder;
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56 |
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57 | /**
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58 | * <p>
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59 | * Trie on which the probability calculations are based.
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60 | * </p>
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61 | */
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62 | protected Trie<Event> trie = null;
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63 |
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64 | /**
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65 | * <p>
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66 | * Random number generator used by probabilistic sequence generation methods.
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67 | * </p>
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68 | */
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69 | protected final Random r;
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70 |
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71 | /**
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72 | * <p>
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73 | * Constructor. Creates a new TrieBasedModel that can be used for stochastic processes with a
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74 | * Markov order less than or equal to {@code markovOrder}.
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75 | * </p>
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76 | *
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77 | * @param markovOrder
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78 | * Markov order of the model
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79 | * @param r
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80 | * random number generator used by probabilistic methods of the class
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81 | * @throws IllegalArgumentException
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82 | * thrown if markovOrder is less than 0 or the random number generator r is null
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83 | */
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84 | public TrieBasedModel(int markovOrder, Random r) {
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85 | super();
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86 | if (markovOrder < 0) {
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87 | throw new IllegalArgumentException("markov order must not be less than 0");
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88 | }
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89 | if (r == null) {
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90 | throw new IllegalArgumentException("random number generator r must not be null");
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91 | }
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92 | this.trieOrder = markovOrder + 1;
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93 | this.r = r;
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94 | }
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95 |
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96 | /**
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97 | * <p>
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98 | * Trains the model by generating a trie from which probabilities are calculated. The trie is
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99 | * newly generated based solely on the passed sequences. If an existing model should only be
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100 | * updated, use {@link #update(Collection)} instead.
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101 | * </p>
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102 | *
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103 | * @param sequences
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104 | * training data
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105 | * @throws IllegalArgumentException
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106 | * thrown is sequences is null
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107 | */
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108 | public void train(Collection<List<Event>> sequences) {
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109 | trie = null;
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110 | update(sequences);
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111 | }
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112 |
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113 | /**
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114 | * <p>
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115 | * Trains the model by updating the trie from which the probabilities are calculated. This
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116 | * function updates an existing trie. In case no trie exists yet, a new trie is generated and
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117 | * the function behaves like {@link #train(Collection)}.
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118 | * </p>
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119 | *
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120 | * @param sequences
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121 | * training data
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122 | * @throws IllegalArgumentException
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123 | * thrown is sequences is null
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124 | */
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125 | public void update(Collection<List<Event>> sequences) {
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126 | if (sequences == null) {
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127 | throw new IllegalArgumentException("sequences must not be null");
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128 | }
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129 | if (trie == null) {
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130 | trie = new Trie<Event>();
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131 | }
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132 | for (List<Event> sequence : sequences) {
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133 | List<Event> currentSequence = new LinkedList<Event>(sequence); // defensive
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134 | // copy
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135 | currentSequence.add(0, Event.STARTEVENT);
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136 | currentSequence.add(Event.ENDEVENT);
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137 |
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138 | trie.train(currentSequence, trieOrder);
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139 | }
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140 | }
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141 |
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142 | /*
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143 | * (non-Javadoc)
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144 | *
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145 | * @see de.ugoe.cs.autoquest.usageprofiles.IStochasticProcess#randomSequence()
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146 | */
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147 | @Override
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148 | public List<Event> randomSequence() {
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149 | return randomSequence(Integer.MAX_VALUE, true);
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150 | }
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151 |
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152 | /*
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153 | * (non-Javadoc)
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154 | *
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155 | * @see de.ugoe.cs.autoquest.usageprofiles.IStochasticProcess#randomSequence()
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156 | */
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157 | @Override
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158 | public List<Event> randomSequence(int maxLength, boolean validEnd) {
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159 | List<Event> sequence = new LinkedList<Event>();
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160 | if (trie != null) {
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161 | boolean endFound = false;
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162 | while (!endFound) { // outer loop for length checking
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163 | sequence = new LinkedList<Event>();
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164 | IncompleteMemory<Event> context = new IncompleteMemory<Event>(trieOrder - 1);
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165 | context.add(Event.STARTEVENT);
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166 |
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167 | while (!endFound && sequence.size() <= maxLength) {
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168 | double randVal = r.nextDouble();
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169 | double probSum = 0.0;
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170 | List<Event> currentContext = context.getLast(trieOrder);
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171 | for (Event symbol : trie.getKnownSymbols()) {
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172 | probSum += getProbability(currentContext, symbol);
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173 | if (probSum >= randVal) {
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174 | if (!(Event.STARTEVENT.equals(symbol) || Event.ENDEVENT.equals(symbol)))
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175 | {
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176 | // only add the symbol the sequence if it is not
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177 | // START or END
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178 | context.add(symbol);
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179 | sequence.add(symbol);
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180 | }
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181 | endFound =
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182 | (Event.ENDEVENT.equals(symbol)) ||
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183 | (!validEnd && sequence.size() == maxLength);
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184 | break;
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185 | }
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186 | }
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187 | }
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188 | }
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189 | }
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190 | return sequence;
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191 | }
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192 |
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193 | /**
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194 | * <p>
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195 | * Returns a Dot representation of the internal trie.
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196 | * </p>
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197 | *
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198 | * @return dot representation of the internal trie
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199 | */
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200 | public String getTrieDotRepresentation() {
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201 | if (trie == null) {
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202 | return "";
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203 | }
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204 | else {
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205 | return trie.getDotRepresentation();
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206 | }
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207 | }
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208 |
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209 | /**
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210 | * <p>
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211 | * Returns a {@link Tree} of the internal trie that can be used for visualization.
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212 | * </p>
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213 | *
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214 | * @return {@link Tree} depicting the internal trie
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215 | */
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216 | public Tree<TrieVertex, Edge> getTrieGraph() {
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217 | if (trie == null) {
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218 | return null;
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219 | }
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220 | else {
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221 | return trie.getGraph();
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222 | }
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223 | }
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224 |
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225 | /**
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226 | * <p>
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227 | * The string representation of the model is {@link Trie#toString()} of {@link #trie}.
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228 | * </p>
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229 | *
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230 | * @see java.lang.Object#toString()
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231 | */
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232 | @Override
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233 | public String toString() {
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234 | if (trie == null) {
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235 | return "";
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236 | }
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237 | else {
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238 | return trie.toString();
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239 | }
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240 | }
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241 |
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242 | /*
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243 | * (non-Javadoc)
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244 | *
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245 | * @see de.ugoe.cs.autoquest.usageprofiles.IStochasticProcess#getNumStates()
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246 | */
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247 | @Override
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248 | public int getNumSymbols() {
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249 | if (trie == null) {
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250 | return 0;
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251 | }
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252 | else {
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253 | return trie.getNumSymbols();
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254 | }
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255 | }
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256 |
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257 | /*
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258 | * (non-Javadoc)
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259 | *
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260 | * @see de.ugoe.cs.autoquest.usageprofiles.IStochasticProcess#getStateStrings()
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261 | */
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262 | @Override
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263 | public String[] getSymbolStrings() {
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264 | if (trie == null) {
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265 | return new String[0];
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266 | }
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267 | String[] stateStrings = new String[getNumSymbols()];
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268 | int i = 0;
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269 | for (Event symbol : trie.getKnownSymbols()) {
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270 | if (symbol.toString() == null) {
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271 | stateStrings[i] = "null";
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272 | }
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273 | else {
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274 | stateStrings[i] = symbol.toString();
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275 | }
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276 | i++;
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277 | }
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278 | return stateStrings;
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279 | }
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280 |
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281 | /*
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282 | * (non-Javadoc)
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283 | *
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284 | * @see de.ugoe.cs.autoquest.usageprofiles.IStochasticProcess#getEvents()
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285 | */
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286 | @Override
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287 | public Collection<Event> getEvents() {
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288 | if (trie == null) {
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289 | return new HashSet<Event>();
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290 | }
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291 | else {
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292 | return trie.getKnownSymbols();
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293 | }
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294 | }
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295 |
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296 | /*
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297 | * (non-Javadoc)
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298 | *
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299 | * @see de.ugoe.cs.autoquest.usageprofiles.IStochasticProcess#generateSequences(int)
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300 | */
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301 | @Override
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302 | public Collection<List<Event>> generateSequences(int length) {
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303 | return generateSequences(length, false);
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304 | }
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305 |
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306 | /*
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307 | * (non-Javadoc)
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308 | *
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309 | * @see de.ugoe.cs.autoquest.usageprofiles.IStochasticProcess#generateSequences(int, boolean)
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310 | */
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311 | @Override
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312 | public Set<List<Event>> generateSequences(int length, boolean fromStart) {
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313 | Set<List<Event>> sequenceSet = new LinkedHashSet<List<Event>>();
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314 | if (length < 1) {
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315 | throw new IllegalArgumentException(
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316 | "Length of generated subsequences must be at least 1.");
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317 | }
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318 | if (length == 1) {
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319 | if (fromStart) {
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320 | List<Event> subSeq = new LinkedList<Event>();
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321 | subSeq.add(Event.STARTEVENT);
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322 | sequenceSet.add(subSeq);
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323 | }
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324 | else {
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325 | for (Event event : getEvents()) {
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326 | List<Event> subSeq = new LinkedList<Event>();
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327 | subSeq.add(event);
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328 | sequenceSet.add(subSeq);
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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 | Collection<Event> events = getEvents();
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334 | Collection<List<Event>> seqsShorter = generateSequences(length - 1, fromStart);
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335 | for (Event event : events) {
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336 | for (List<Event> seqShorter : seqsShorter) {
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337 | Event lastEvent = event;
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338 | if (getProbability(seqShorter, lastEvent) > 0.0) {
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339 | List<Event> subSeq = new ArrayList<Event>(seqShorter);
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340 | subSeq.add(lastEvent);
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341 | sequenceSet.add(subSeq);
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342 | }
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343 | }
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344 | }
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345 | return sequenceSet;
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346 | }
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347 |
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348 | /*
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349 | * (non-Javadoc)
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350 | *
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351 | * @see de.ugoe.cs.autoquest.usageprofiles.IStochasticProcess#generateValidSequences (int)
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352 | */
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353 | @Override
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354 | public Collection<List<Event>> generateValidSequences(int length) {
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355 | // check for min-length implicitly done by generateSequences
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356 | Collection<List<Event>> allSequences = generateSequences(length, true);
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357 | Collection<List<Event>> validSequences = new LinkedHashSet<List<Event>>();
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358 | for (List<Event> sequence : allSequences) {
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359 | if (sequence.size() == length &&
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360 | Event.ENDEVENT.equals(sequence.get(sequence.size() - 1)))
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361 | {
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362 | validSequences.add(sequence);
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363 | }
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364 | }
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365 | return validSequences;
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366 | }
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367 |
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368 | /*
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369 | * (non-Javadoc)
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370 | *
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371 | * @see de.ugoe.cs.autoquest.usageprofiles.IStochasticProcess#getProbability(java.util .List)
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372 | */
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373 | @Override
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374 | public double getProbability(List<Event> sequence) {
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375 | if (sequence == null) {
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376 | throw new IllegalArgumentException("sequence must not be null");
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377 | }
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378 | double prob = 1.0;
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379 | List<Event> context = new LinkedList<Event>();
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380 | for (Event event : sequence) {
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381 | prob *= getProbability(context, event);
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382 | context.add(event);
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383 | }
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384 | return prob;
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385 | }
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386 |
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387 | /*
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388 | * (non-Javadoc)
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389 | *
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390 | * @see de.ugoe.cs.autoquest.usageprofiles.IStochasticProcess#getNumFOMStates()
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391 | */
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392 | @Override
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393 | public int getNumFOMStates() {
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394 | if (trie == null) {
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395 | return 0;
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396 | }
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397 | else {
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398 | return trie.getNumLeafAncestors();
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399 | }
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400 | }
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401 |
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402 | /*
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403 | * (non-Javadoc)
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404 | *
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405 | * @see de.ugoe.cs.autoquest.usageprofiles.IStochasticProcess#getNumTransitions()
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406 | */
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407 | @Override
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408 | public int getNumTransitions() {
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409 | if (trie == null) {
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410 | return 0;
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411 | }
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412 | else {
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413 | return trie.getNumLeafs();
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414 | }
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415 | }
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416 | }
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