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.util.Collection;
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5 | import java.util.List;
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6 |
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7 | import de.ugoe.cs.quest.eventcore.Event;
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8 |
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9 | /**
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10 | * <p>
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11 | * This interface defines the functionalities provided by stochastic processes.
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12 | * </p>
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13 | *
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14 | * @author Steffen Herbold
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15 | * @version 1.0
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16 | */
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17 | public interface IStochasticProcess extends Serializable {
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18 |
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19 | /**
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20 | * <p>
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21 | * Returns the probability, that the next event is {@code symbol} given the last events are
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22 | * {@code context}. The last element of {@code context} is the most recent in the history, the
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23 | * first element is the oldest.
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24 | * </p>
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25 | *
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26 | * @param context
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27 | * recently observed symbols
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28 | * @param symbol
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29 | * event for which the probability is calculated
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30 | * @return probabilty the {@code symbol} is the next event, given the last events
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31 | * {@code context}
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32 | * @throws IllegalArgumentException
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33 | * thrown if context or symbol is null
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34 | */
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35 | double getProbability(List<Event> context, Event symbol);
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36 |
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37 | /**
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38 | * <p>
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39 | * Returns the probabilitiy that a given sequence is generated by the stochastic process.
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40 | * </p>
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41 | *
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42 | * @param sequence
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43 | * sequences of which the probability is calculated
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44 | * @return probability of the sequences; 1.0 if sequence is empty or null
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45 | * @throws IllegalArgumentException
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46 | * thrown if sequence is null
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47 | */
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48 | double getProbability(List<Event> sequence);
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49 |
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50 | /**
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51 | * <p>
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52 | * Generates a random sequence of events. The sequence starts with {@link Event#STARTEVENT} and
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53 | * finishes with {@link Event#ENDEVENT}.
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54 | * </p>
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55 | *
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56 | * @return randomly generated sequence
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57 | */
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58 | public List<Event> randomSequence();
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59 |
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60 | /**
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61 | * <p>
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62 | * Generates a random sequence of events. The sequence starts with {@link Event#STARTEVENT} and
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63 | * finishes with
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64 | * <ul>
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65 | * <li>{@link Event#ENDEVENT} if validEnd==true.</li>
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66 | * <li>b) if a generated sequences reaches {@link Event#ENDEVENT} before maxLength, the sequence
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67 | * finishes and is shorter than maxLenght. Otherwise, the sequence finishes as soon as maxLength
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68 | * is reached and the final event of the sequence must not be {@link Event#ENDEVENT}.</li>
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69 | * </ul>
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70 | * </p>
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71 | *
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72 | * @param maxLength
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73 | * maximum length of the generated sequence
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74 | * @param validEnd
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75 | * if true, only sequences that finish with {@link Event#ENDEVENT} are generated
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76 | * @return randomly generated sequence
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77 | *
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78 | */
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79 | public List<Event> randomSequence(int maxLength, boolean validEnd);
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80 |
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81 | /**
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82 | * <p>
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83 | * Generates all sequences of a given length are possible, i.e., have a positive probability.<br>
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84 | * All states are used as possible starting states.
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85 | * </p>
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86 | *
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87 | * @param length
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88 | * length of the generated sequences
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89 | * @return generated sequences
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90 | * @see #generateSequences(int, boolean)
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91 | * @throws IllegalArgumentException
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92 | * thrown if length is less than or equal to 0
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93 | */
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94 | public Collection<List<Event>> generateSequences(int length);
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95 |
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96 | /**
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97 | * <p>
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98 | * Generates all sequences of given length that can are possible, i.e., have positive
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99 | * probability.<br>
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100 | * If {@code fromStart==true}, all generated sequences start in {@link Event#STARTEVENT}.
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101 | * Otherwise this method is the same as {@link #generateSequences(int)}.
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102 | * </p>
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103 | *
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104 | * @param length
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105 | * length of the generated sequences
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106 | * @param fromStart
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107 | * if true, all generated sequences start with {@link Event#STARTEVENT}
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108 | * @return generated sequences
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109 | * @throws IllegalArgumentException
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110 | * thrown if length is less than or equal to 0
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111 | */
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112 | public Collection<List<Event>> generateSequences(int length, boolean fromStart);
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113 |
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114 | /**
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115 | * <p>
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116 | * Generates all sequences starting with {@link Event#STARTEVENT} and finishing with
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117 | * {@link Event#ENDEVENT} of a given length. It is possible that no such sequence exists with
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118 | * the defined length and the returned set is empty. If {@code length} is less than 2 the
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119 | * returned set is always empty.
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120 | * </p>
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121 | *
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122 | * @param length
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123 | * @return generated sequences
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124 | * @throws IllegalArgumentException
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125 | * thrown if length is less than or equal to 0
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126 | */
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127 | public Collection<List<Event>> generateValidSequences(int length);
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128 |
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129 | /**
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130 | * <p>
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131 | * Returns the number of states known by the stochastic process, i.e., the size of its alphabet.
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132 | * </p>
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133 | *
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134 | * @return number of states
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135 | */
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136 | public int getNumSymbols();
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137 |
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138 | /**
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139 | * <p>
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140 | * Returns a string representation of all known states.
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141 | * </p>
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142 | *
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143 | * @return string representation for all known states
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144 | */
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145 | public String[] getSymbolStrings();
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146 |
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147 | /**
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148 | * <p>
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149 | * Returns the number of states the process would have if it would be flattened through
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150 | * state-splitting to a first-order Markov model.
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151 | * </p>
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152 | * <p>
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153 | * If it is not possible to flatten the model, -1 is returned.
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154 | * </p>
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155 | *
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156 | * @return number of states an equivalent FOM would have; -1 if not available
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157 | */
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158 | public int getNumFOMStates();
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159 |
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160 | /**
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161 | * <p>
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162 | * Returns the number of transitions the process would have if it would be flattened through
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163 | * state-splitting to a first-order Markov model.
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164 | * </p>
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165 | *
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166 | * @return number of transitions an equivalent FOM would have; -1 if not available
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167 | */
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168 | public int getNumTransitions();
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169 |
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170 | /**
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171 | * <p>
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172 | * Returns all states known by the stochastic process, i.e., its {@link Event}s.
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173 | * </p>
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174 | *
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175 | * @return events known by the process
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176 | */
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177 | public Collection<Event> getEvents();
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178 |
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179 | }
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