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/*******************************************************************************
* Copyright (c) 2010-2014, Miklos Foldenyi, Andras Szabolcs Nagy, Abel Hegedus, Akos Horvath, Zoltan Ujhelyi and Daniel Varro
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0 which is available at
* http://www.eclipse.org/legal/epl-v20.html.
*
* SPDX-License-Identifier: EPL-2.0
*******************************************************************************/
package org.eclipse.viatra.dse.statecode;
import org.eclipse.emf.common.notify.Notifier;
import org.eclipse.viatra.query.runtime.api.IPatternMatch;
/**
* <p>
* To be able to efficiently explore a design space, a state that has been explored before through an other trajectory
* needs to be recognized and ignored accordingly.
* </p>
*
* <p>
* This is done by generating a pseudo-unique value (object) that is only depended on the relevant parts of the model's
* internal state, that is, the values of two states can only be equal if the states themselves can be considered equal.
* </p>
*
* <p>
* The processing engine however assumes, that any two states that share this pseudo-unique value has the same
* characteristics, meaning they have the same amount and type of outgoing transitions available, and firing the
* appropriate transitions from both states also result in states that share their pseudo-unique identifier. If this
* condition is not satisfied, the exploration process's result will be non-deterministic, and in consequence, solutions
* can be lost.
* </p>
*
* <p>
* In addition to providing pseudo-unique identifiers to model states, the state coder must provide pseud-unique
* identifiers to the outgoing transitions as well, but they only need to be unique on the scope of the particular
* state, not globally. Global addressing thus can be achieved by considering the pseudo-unique identifier of the state
* and the pseudo-unique identifier of the transition together if needed.
* </p>
*
* <p>
* Both identifiers can be arbitrary objects, and equality is checked by calling {@link Object#equals(Object)} on the
* two identifiers.
* </p>
*
* <p>
* For any particular implementation an {@link IStateCoderFactory} implementation must also be supplied that handles the
* creation of {@link IStateCoder} instances.
* </p>
*
* <p>
* Usually it is unnecessary to represent everything from the model in a state code, only the parts which are modified
* by the transformation rules.
* </p>
*
* @author Miklos Foldenyi, Andras Szabolcs Nagy
*
*/
public interface IStateCoder {
/**
* Initializes the state coder on the given model.
*
* @param notifier
*/
void init(Notifier notifier);
/**
* Returns a pseudo-unique identifier that describes the underlying model's current internal state.
*
* @return an arbitrary {@link Object} that can be used as the identifier.
*/
Object createStateCode();
/**
* Returns a pseudo-unique identifier that describes the given {@link IPatternMatch} in the context of the
* underlying model's current internal state.
*
* @return an arbitrary {@link Object} that can be used as the identifier in the given state.
*/
Object createActivationCode(IPatternMatch match);
}
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