Extensible select and enumeration types

and their elements in schema Product_group_arm taking into account BASED_ON types


 classification_item - EXTENSIBLE GENERIC_ENTITY SELECT
          Product_group
          Product_group_relationship

 date_or_date_time_item - EXTENSIBLE SELECT

 effectivity_item - EXTENSIBLE SELECT
          Product_group
          Product_group_membership
          Product_group_relationship

 identification_item - EXTENSIBLE SELECT
          Product_as_individual
          Product_as_individual_version
          Product_as_individual_view

 measure_value - EXTENSIBLE SELECT
          any_number_value
          any_string_value
          length_measure
          plane_angle_measure

 product_select - EXTENSIBLE SELECT
          Product
          Product_as_individual
          Product_concept
          Product_group
          Product_version

 property_assignment_select - EXTENSIBLE SELECT
          Product_group_membership

 represented_definition - EXTENSIBLE SELECT
          Assigned_property
          Independent_property