[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.List;
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| 7 |
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| 8 | import de.ugoe.cs.quest.eventcore.Event;
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| 9 |
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| 10 | /**
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| 11 | * <p>
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| 12 | * This interface defines the functionalities provided by stochastic processes.
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| 13 | * </p>
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| 14 | *
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| 15 | * @author Steffen Herbold
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| 16 | * @version 1.0
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| 17 | */
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| 18 | public interface IStochasticProcess extends Serializable {
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| 19 |
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| 20 | /**
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| 21 | * <p>
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| 22 | * Returns the probability, that the next event is {@code symbol} given the
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| 23 | * last events are {@code context}. The last element of {@code context} is
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| 24 | * the most recent in the history, the first element is the oldest.
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| 25 | * </p>
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| 26 | *
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| 27 | * @param context
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| 28 | * recently observed symbols
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| 29 | * @param symbol
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| 30 | * event for which the probability is calculated
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| 31 | * @return probabilty the {@code symbol} is the next event, given the last
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| 32 | * events {@code context}
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| 33 | * @throws InvalidParameterException
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| 34 | * thrown if context or symbol is null
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| 35 | */
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| 36 | double getProbability(List<? extends Event<?>> context, Event<?> symbol);
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| 37 |
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| 38 | /**
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| 39 | * <p>
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| 40 | * Returns the probabilitiy that a given sequence is generated by the
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| 41 | * stochastic process.
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| 42 | * </p>
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| 43 | *
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| 44 | * @param sequence
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| 45 | * sequences of which the probability is calculated
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| 46 | * @return probability of the sequences; 1.0 if sequence is empty or null
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| 47 | * @throws InvalidParameterException
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| 48 | * thrown if sequence is null
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| 49 | */
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| 50 | double getProbability(List<? extends Event<?>> sequence);
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| 51 |
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| 52 | /**
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| 53 | * <p>
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| 54 | * Generates a random sequence of events. The sequence starts with
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| 55 | * {@link Event#STARTEVENT} and finishes with {@link Event#ENDEVENT}.
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| 56 | * </p>
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| 57 | *
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| 58 | * @return randomly generated sequence
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| 59 | */
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| 60 | public List<? extends Event<?>> randomSequence();
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| 61 |
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| 62 | /**
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| 63 | * <p>
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| 64 | * Generates a random sequence of events. The sequence starts with
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| 65 | * {@link Event#STARTEVENT} and finishes with
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| 66 | * <ul>
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| 67 | * <li>{@link Event#ENDEVENT} if validEnd==true.</li>
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| 68 | * <li>b) if a generated sequences reaches {@link Event#ENDEVENT} before
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| 69 | * maxLength, the sequence finishes and is shorter than maxLenght.
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| 70 | * Otherwise, the sequence finishes as soon as maxLength is reached and the
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| 71 | * final event of the sequence must not be {@link Event#ENDEVENT}.</li>
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| 72 | * </ul>
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| 73 | * </p>
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| 74 | *
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| 75 | * @param maxLength
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| 76 | * maximum length of the generated sequence
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| 77 | * @param validEnd
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| 78 | * if true, only sequences that finish with
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| 79 | * {@link Event#ENDEVENT} are generated
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| 80 | * @return randomly generated sequence
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| 81 | *
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| 82 | */
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| 83 | public List<? extends Event<?>> randomSequence(int maxLength,
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| 84 | boolean validEnd);
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| 85 |
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| 86 | /**
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| 87 | * <p>
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| 88 | * Generates all sequences of a given length are possible, i.e., have a
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| 89 | * positive probability.<br>
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| 90 | * All states are used as possible starting states.
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| 91 | * </p>
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| 92 | *
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| 93 | * @param length
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| 94 | * length of the generated sequences
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| 95 | * @return generated sequences
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| 96 | * @see #generateSequences(int, boolean)
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| 97 | * @throws InvalidParameterException
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| 98 | * thrown if length is less than or equal to 0
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| 99 | */
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| 100 | public Collection<List<? extends Event<?>>> generateSequences(int length);
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| 101 |
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| 102 | /**
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| 103 | * <p>
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| 104 | * Generates all sequences of given length that can are possible, i.e., have
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| 105 | * positive probability.<br>
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| 106 | * If {@code fromStart==true}, all generated sequences start in
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| 107 | * {@link Event#STARTEVENT}. Otherwise this method is the same as
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| 108 | * {@link #generateSequences(int)}.
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| 109 | * </p>
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| 110 | *
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| 111 | * @param length
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| 112 | * length of the generated sequences
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| 113 | * @param fromStart
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| 114 | * if true, all generated sequences start with
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| 115 | * {@link Event#STARTEVENT}
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| 116 | * @return generated sequences
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| 117 | * @throws InvalidParameterException
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| 118 | * thrown if length is less than or equal to 0
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| 119 | */
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| 120 | public Collection<List<? extends Event<?>>> generateSequences(int length,
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| 121 | boolean fromStart);
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| 122 |
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| 123 | /**
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| 124 | * <p>
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| 125 | * Generates all sequences starting with {@link Event#STARTEVENT} and
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| 126 | * finishing with {@link Event#ENDEVENT} of a given length. It is possible
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| 127 | * that no such sequence exists with the defined length and the returned set
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| 128 | * is empty. If {@code length} is less than 2 the returned set is always
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| 129 | * empty.
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| 130 | * </p>
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| 131 | *
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| 132 | * @param length
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| 133 | * @return generated sequences
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| 134 | * @throws InvalidParameterException
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| 135 | * thrown if length is less than or equal to 0
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| 136 | */
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| 137 | public Collection<List<? extends Event<?>>> generateValidSequences(
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| 138 | int length);
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| 139 |
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| 140 | /**
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| 141 | * <p>
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| 142 | * Returns the number of states known by the stochastic process, i.e., the
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| 143 | * size of its alphabet.
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| 144 | * </p>
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| 145 | *
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| 146 | * @return number of states
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| 147 | */
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| 148 | public int getNumSymbols();
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| 149 |
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| 150 | /**
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| 151 | * <p>
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| 152 | * Returns a string representation of all known states.
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| 153 | * </p>
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| 154 | *
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| 155 | * @return string representation for all known states
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| 156 | */
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| 157 | public String[] getSymbolStrings();
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| 158 |
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| 159 | /**
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| 160 | * <p>
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| 161 | * Returns the number of states the process would have if it would be
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| 162 | * flattened through state-splitting to a first-order Markov model.
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| 163 | * </p>
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| 164 | * <p>
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| 165 | * If it is not possible to flatten the model, -1 is returned.
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| 166 | * </p>
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| 167 | *
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| 168 | * @return number of states an equivalent FOM would have; -1 if not
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| 169 | * available
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| 170 | */
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| 171 | public int getNumFOMStates();
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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 transitions the process would have if it would be
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| 176 | * flattened through state-splitting to a first-order Markov model.
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| 177 | * </p>
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| 178 | *
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| 179 | * @return number of transitions an equivalent FOM would have; -1 if not
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| 180 | * available
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| 181 | */
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| 182 | public int getNumTransitions();
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| 183 |
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| 184 | /**
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| 185 | * <p>
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| 186 | * Returns all states known by the stochastic process, i.e., its
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| 187 | * {@link Event}s.
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| 188 | * </p>
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| 189 | *
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| 190 | * @return events known by the process
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| 191 | */
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| 192 | public Collection<? extends Event<?>> getEvents();
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| 193 |
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| 194 | } |
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