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package org.apache.cayenne.graph;

import java.io.Serializable;

/**
 * Represents a change in an object graph. This can be a simple change (like a node
 * property update) or a composite change that consists of a number of smaller changes.
 * 
 * @since 1.2
 * @author Andrus Adamchik
 */
public interface GraphDiff extends Serializable {

    /**
     * Returns true if this diff is simply a placeholder and does not perform any actual
     * operation.
     */
    boolean isNoop();

    /**
     * Calls appropriate methods on the handler to "replay" this change.
     */
    void apply(GraphChangeHandler handler);

    /**
     * Calls appropriate methods on the handler to revert this change.
     */
    void undo(GraphChangeHandler handler);
}
