code: public ExtendedRelation addRelationship(String baseTableName,
  			String relatedTableName, UserMappingTable userMappingTable,
  			RelationType relationType) {
  		return addRelationship(baseTableName, relatedTableName,
  				userMappingTable, relationType.getName());
  	}
docs: Adds a relationship between the base and related table. Creates the user
  mapping table if needed.
  
  @param baseTableName
  base table name
  @param relatedTableName
  related table name
  @param userMappingTable
  user mapping table
  @param relationType
  relation type
  @return The relationship that was added