code: @Nonnull
    public EChange queueWorkItem (@Nonnull final IParticipantIdentifier aParticipantID,
                                  @Nonnull final EIndexerWorkItemType eType,
                                  @Nonnull @Nonempty final String sOwnerID,
                                  @Nonnull @Nonempty final String sRequestingHost)
    {
      // Build item
      final IIndexerWorkItem aWorkItem = new IndexerWorkItem (aParticipantID, eType, sOwnerID, sRequestingHost);
      // And queue it
      return _queueUniqueWorkItem (aWorkItem);
    }
docs: Queue a new work item
  
  @param aParticipantID
  Participant ID to use.
  @param eType
  Action type.
  @param sOwnerID
  Owner of this action
  @param sRequestingHost
  Requesting host (IP address)
  @return {@link EChange#UNCHANGED} if the item was queued,
  {@link EChange#UNCHANGED} if this item is already in the queue!