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  package org.apache.cayenne.dbsync.merge.token;
  
  import org.apache.cayenne.dbsync.merge.context.MergeDirection;
  import org.apache.cayenne.dbsync.merge.context.MergerContext;
  import org.apache.cayenne.dbsync.merge.factory.MergerTokenFactory;
  
  /**
   * Represents a minimal atomic synchronization operation between database and Cayenne model.
   */
  public interface MergerToken extends Comparable<MergerToken> {
  
      String getTokenName();
  
      String getTokenValue();
  
      int getSortingWeight();
  
      /**
       * The direction of this token. One of {@link MergeDirection#TO_DB} or
       * {@link MergeDirection#TO_MODEL}
       */
      MergeDirection getDirection();
  
      /**
       * Create a complimentary token with the reverse direction. AddColumn in one direction becomes
       * DropColumn in the other direction.
       * <p>
       * Not all tokens are reversible.
       */
      MergerToken createReverse(MergerTokenFactory factory);
  
      /**
       * Executes synchronization operation.
       *
       * @param context merge operation context.
       */
      void execute(MergerContext context);
  
      boolean isEmpty();
  
  }
  